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Title: The Riddle of the Universe at the close of the nineteenth century
Author: Haeckel, Ernst, 1834-1919
Language: English
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    Every effort has been made to replicate this text as faithfully as
    possible, including inconsistencies in hyphenation. It seems that
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[Illustration: ERNST HAECKEL]

                               THE RIDDLE
                            OF THE UNIVERSE

                            _AT THE CLOSE OF
                        THE NINETEENTH CENTURY_


                             ERNST HAECKEL

            (Ph.D., M.D., LL.D., Sc.D., and Professor at the
                          University of Jena)

                      "THE EVOLUTION OF MAN" ETC.

                             TRANSLATED BY

                             JOSEPH McCABE


                      HARPER & BROTHERS PUBLISHERS
                          NEW YORK AND LONDON

                 Copyright, 1900, by HARPER & BROTHERS.

                         _All rights reserved._



    AUTHOR'S PREFACE                      v

    TRANSLATOR'S PREFACE                 xi

    THE NATURE OF THE PROBLEM             1

    OUR BODILY FRAME                     22

    OUR LIFE                             39



    THE NATURE OF THE SOUL               88

    PSYCHIC GRADATIONS                  108


    THE PHYLOGENY OF THE SOUL           148

    CONSCIOUSNESS                       170


    THE LAW OF SUBSTANCE                211


    THE UNITY OF NATURE                 254

    GOD AND THE WORLD                   275

    KNOWLEDGE AND BELIEF                292


    OUR MONISTIC RELIGION               331

    OUR MONISTIC ETHICS                 347


    CONCLUSION                          380

    INDEX                               385


The present study of the monistic philosophy is intended for thoughtful
readers of every condition who are united in an honest search for the
truth. An intensification of this effort of man to attain a knowledge
of the truth is one of the most salient features of the nineteenth
century. That is easily explained, in the first place, by the immense
progress of science, especially in its most important branch, the
history of humanity; it is due, in the second place, to the open
contradiction that has developed during the century between science
and the traditional "Revelation"; and, finally, it arises from the
inevitable extension and deepening of the rational demand for an
elucidation of the innumerable facts that have been recently brought to
light, and for a fuller knowledge of their causes.

Unfortunately, this vast progress of empirical knowledge in our
"Century of Science" has not been accompanied by a corresponding
advancement of its theoretical interpretation--that higher knowledge of
the causal nexus of individual phenomena which we call philosophy. We
find, on the contrary, that the abstract and almost wholly metaphysical
science which has been taught in our universities for the last hundred
years under the name of "philosophy" is far from assimilating our
hard-earned treasures of experimental research. On the other hand, we
have to admit, with equal regret, that most of the representatives
of what is called "exact science" are content with the special care
of their own narrow branches of observation and experiment, and
deem superfluous the deeper study of the universal connection of
the phenomena they observe--that is, philosophy. While these pure
empiricists "do not see the wood for the trees," the metaphysicians, on
the other hand, are satisfied with the mere picture of the wood, and
trouble not about its individual trees. The idea of a "philosophy of
nature," to which both those methods of research, the empirical and the
speculative, naturally converge, is even yet contemptuously rejected by
large numbers of representatives of both tendencies.

This unnatural and fatal opposition between science and philosophy,
between the results of experience and of thought, is undoubtedly
becoming more and more onerous and painful to thoughtful people. That
is easily proved by the increasing spread of the immense popular
literature of "natural philosophy" which has sprung up in the course
of the last half-century. It is seen, too, in the welcome fact that,
in spite of the mutual aversion of the scientific observer and the
speculative philosopher, nevertheless eminent thinkers from both
camps league themselves in a united effort to attain the solution
of that highest object of inquiry which we briefly denominate the
"world-riddles." The studies of these "world-riddles" which I offer in
the present work cannot reasonably claim to give a perfect solution of
them; they merely offer to a wide circle of readers a critical inquiry
into the problem, and seek to answer the question as to how nearly we
have approached that solution at the present day. What stage in the
attainment of truth have we actually arrived at in this closing year of
the nineteenth century? What progress have we really made during its
course towards that immeasurably distant goal?

The answer which I give to these great questions must, naturally, be
merely subjective and only partly correct; for my knowledge of nature
and my ability to interpret its objective reality are limited, as are
those of every man. The one point that I can claim for it, and which,
indeed, I must ask of my strongest opponents, is that my Monistic
Philosophy is sincere from beginning to end--it is the complete
expression of the conviction that has come to me, after many years of
ardent research into Nature and unceasing reflection, as to the true
basis of its phenomena. For fully half a century has my mind's work
proceeded, and I now, in my sixty-sixth year, may venture to claim
that it is mature; I am fully convinced that this "ripe fruit" of the
tree of knowledge will receive no important addition and suffer no
substantial modification during the brief spell of life that remains to

I presented all the essential and distinctive elements of my monistic
and genetic philosophy thirty-three years ago, in my _General
Morphology of Organisms_, a large and laborious work, which has had but
a limited circulation. It was the first attempt to apply in detail the
newly established theory of evolution to the whole science of organic
forms. In order to secure the acceptance of at least one part of the
new thought which it contained, and to kindle a wider interest in the
greatest advancement of knowledge that our century has witnessed, I
published my _Natural History of Creation_ two years afterwards.
As this less complicated work, in spite of its great defects, ran
into nine large editions and twelve different translations, it has
contributed not a little to the spread of monistic views. The same
may be said of the less known _Anthropogeny_[1] (1874), in which I
set myself the difficult task of rendering the most important facts
of the theory of man's descent accessible and intelligible to the
general reader; the fourth, enlarged, edition of that work appeared in
1891. In the paper which I read at the fourth International Congress
of Zoology at Cambridge, in 1898, on "Our Present Knowledge of the
Descent of Man"[2] (a seventh edition of which appeared in 1899), I
treated certain significant and particularly valuable advances which
this important branch of anthropology has recently made. Other isolated
questions of our modern natural philosophy, which are peculiarly
interesting, have been dealt with in my _Collected Popular Lectures on
the Subject of Evolution_ (1878). Finally, I have briefly presented
the broad principles of my monistic philosophy and its relation to the
dominant faith in my _Confession of Faith of a Man of Science: Monism
as a Connecting Link between Religion and Science_[3] (1892, eighth
edition, 1899).

The present work on _The Riddle of the Universe_ is the continuation,
confirmation, and integration of the views which I have urged for a
generation in the aforesaid volumes. It marks the close of my studies
on the monistic conception of the universe. The earlier plan, which
I projected many years ago, of constructing a complete "System of
Monistic Philosophy" on the basis of evolution will never be carried
into effect now. My strength is no longer equal to the task, and many
warnings of approaching age urge me to desist. Indeed, I am wholly a
child of the nineteenth century, and with its close I draw the line
under my life's work.

The vast extension of human knowledge which has taken place during
the present century, owing to a happy division of labor, makes
it impossible to-day to range over all its branches with equal
thoroughness, and to show their essential unity and connection.
Even a genius of the highest type, having an equal command of every
branch of science, and largely endowed with the artistic faculty of
comprehensive presentation, would be incapable of setting forth a
complete view of the cosmos in the space of a moderate volume. My own
command of the various branches of science is uneven and defective,
so that I can attempt no more than to sketch the general plan of such
a world-picture, and point out the pervading unity of its parts,
however imperfect be the execution. Thus it is that this work on the
world-enigma has something of the character of a sketch-book, in which
studies of unequal value are associated. As the material of the book
was partly written many years ago, and partly produced for the first
time during the last few years, the composition is, unfortunately,
uneven at times; repetitions, too, have proved unavoidable. I trust
those defects will be overlooked.

In taking leave of my readers, I venture the hope that, through my
sincere and conscientious work--in spite of its faults, of which I am
not unconscious--I have contributed a little towards the solution
of the great enigma. Amid the clash of theories, I trust that I have
indicated to many a reader who is absorbed in the zealous pursuit of
purely rational knowledge that path which, it is my firm conviction,
alone leads to the truth--the path of empirical investigation and of
the Monistic Philosophy which is based upon it.

                                                          ERNST HAECKEL.



The hour is close upon us when we shall commence our retrospect of one
of the most wonderful sections of time that was ever measured by the
sweep of the earth. Already the expert is at work, dissecting out and
studying his particular phase of that vast world of thought and action
we call the nineteenth century. Art, literature, commerce, industry,
politics, ethics--all have their high interpreters among us; but in
the chance of life it has fallen out that there is none to read aright
for us, in historic retrospect, what after ages will probably regard
as the most salient feature of the nineteenth century--the conflict
of theology with philosophy and science. The pens of our Huxleys,
and Tyndalls, and Darwins lie where they fell; there is none left in
strength among us to sum up the issues of that struggle with knowledge
and sympathy.

In these circumstances it has been thought fitting that we should
introduce to English readers the latest work of Professor Haeckel.
Germany, as the reader will quickly perceive, is witnessing the same
strange reaction of thought that we see about us here in England,
yet _Die Welträthsel_ found an immediate and very extensive circle
of readers. One of the most prominent zoologists of the century,
Professor Haeckel, has a unique claim to pronounce with authority, from
the scientific side, on what is known as "the conflict of science and
religion." In the contradictory estimates that are urged on us--for
the modern ecclesiastic is as emphatic in his assurance that the
conflict has ended favorably to theology as the rationalist is with his
counter-assertion--the last words of one of the leading combatants of
the second half of the century, still, happily, in full vigor of mind,
will be heard with respect and close attention.

A glance at the index of the work suffices to indicate its comprehensive
character. The judgment of the distinguished scientist cannot fail
to have weight on all the topics included; yet the reader will soon
discover a vein of exceptionally interesting thought in the chapters
on evolution. The evolution of the human body is no longer a matter
of serious dispute. It has passed the first two tribunals--those of
theology and of an _à priori_ philosophy--and is only challenged at the
third and last--that of empirical proof--by the decorative heads of
scientific bodies and a few isolated thinkers.

    "_Apparent rari nantes in gurgite vasto._"

But the question of the evolution of the human mind, or soul, has been
successfully divorced from that of the body. Roman Catholic advanced
theologians, whose precise terminology demanded a clear position, admit
the latter and deny the former categorically. Other theologians, and
many philosophers, have still a vague notion that the evidence for
the one does not impair their sentimental objection to the other. Dr.
Haeckel's work summarizes the evidence for the evolution of mind in
a masterly and profoundly interesting fashion. It seems impossible to
follow his broad survey of the psychic world, from protist to man,
without bearing away a conviction of the natural origin of every power
and content of the human soul.


_October, 1900._




    The Condition of Civilization and of Thought at the Close of
    the Nineteenth Century--Progress of Our Knowledge of Nature,
    of the Organic and Inorganic Sciences--The Law of Substance
    and the Law of Evolution--Progress of Technical Science and
    of Applied Chemistry--Stagnancy in other Departments of
    Life: Legal and Political Administration, Education, and the
    Church--Conflict of Reason and Dogma--Anthropism--Cosmological
    Perspective--Cosmological Theorems--Refutation of the Delusion
    of Man's Importance--Number of "World-Riddles"--Criticism of
    the "Seven" Enigmas--The Way to Solve Them--Function of the
    Senses and of the Brain--Induction and Deduction--Reason,
    Sentiment, and Revelation--Philosophy and Science--Experience and
    Speculation--Dualism and Monism

The close of the nineteenth century offers one of the most remarkable
spectacles to the thoughtful observer. All educated people are
agreed that it has in many respects immeasurably outstripped its
predecessors, and has achieved tasks that were deemed impracticable at
its commencement. An entirely new character has been given to the whole
of our modern civilization, not only by our astounding theoretical
progress in sound knowledge of nature, but also by the remarkably
fertile practical application of that knowledge in technical science,
industry, commerce, and so forth. On the other hand, however, we have
made little or no progress in moral and social life, in comparison with
earlier centuries; at times there has been serious reaction. And from
this obvious conflict there have arisen, not only an uneasy sense of
dismemberment and falseness, but even the danger of grave catastrophes
in the political and social world. It is, then, not merely the right,
but the sacred duty, of every honorable and humanitarian thinker to
devote himself conscientiously to the settlement of that conflict,
and to warding off the dangers that it brings in its train. In our
conviction this can only be done by a courageous effort to attain the
truth, and by the formation of a clear view of the world--a view that
shall be based on truth and conformity to reality.

If we recall to mind the imperfect condition of science at the
beginning of the century, and compare this with the magnificent
structure of its closing years, we are compelled to admit that
marvellous progress has been made during its course. Every single
branch of science can boast that it has, especially during the latter
half of the century, made numerous acquisitions of the utmost value.
Both in our microscopic knowledge of the little and in our telescopic
investigation of the great we have attained an invaluable insight
that seemed inconceivable a hundred years ago. Improved methods of
microscopic and biological research have not only revealed to us an
invisible world of living things in the kingdom of the protists, full
of an infinite wealth of forms, but they have taught us to recognize in
the tiny cell the all-pervading "elementary organism" of whose social
communities--the tissues--the body of every multicellular plant and
animal, even that of man, is composed. This anatomical knowledge is
of extreme importance; and it is supplemented by the embryological
discovery that each of the higher multicellular organisms is developed
out of one simple cell, the impregnated ovum. The "cellular theory,"
which has been founded on that discovery, has given us the first true
interpretation of the physical, chemical, and even the psychological
processes of life--those mysterious phenomena for whose explanation
it had been customary to postulate a supernatural "vital force" or
"immortal soul." Moreover, the true character of disease has been made
clear and intelligible to the physician for the first time by the
cognate science of Cellular Pathology.

The discoveries of the nineteenth century in the inorganic world are no
less important. Physics has made astounding progress in every section
of its province--in optics and acoustics, in magnetism and electricity,
in mechanics and thermo-dynamics; and, what is still more important,
it has proved the unity of the forces of the entire universe. The
mechanical theory of heat has shown how intimately they are connected,
and how each can, in certain conditions, transform itself directly
into another. Spectral analysis has taught us that the same matter
which enters into the composition of all bodies on earth, including
its living inhabitants, builds up the rest of the planets, the sun,
and the most distant stars. Astro-physics has considerably enlarged
our cosmic perspective in revealing to us, in the immeasurable depths
of space, millions of circling spheres larger than our earth, and,
like it, in endless transformation, in an eternal rhythm of life and
death. Chemistry has introduced us to a multitude of new substances,
all of which arise from the combination of a few (about seventy)
elements that are incapable of further analysis; some of them play a
most important part in every branch of life. It has been shown that one
of these elements--carbon--is the remarkable substance that effects
the endless variety of organic syntheses, and thus may be considered
"the chemical basis of life." All the particular advances, however, of
physics and chemistry yield in theoretical importance to the discovery
of the great law which brings them all to one common focus, the "Law
of Substance." As this fundamental cosmic law establishes the eternal
persistence of matter and force, their unvarying constancy throughout
the entire universe, it has become the pole-star that guides our
Monistic Philosophy through the mighty labyrinth to a solution of the

Since we intend to make a general survey of the actual condition of
our knowledge of nature and its progress during the present century in
the following chapters, we shall delay no longer with the review of
its particular branches. We would only mention one important advance,
which was contemporary with the discovery of the law of substance, and
which supplements it--the establishment of the theory of evolution.
It is true that there were philosophers who spoke of the evolution
of things a thousand years ago; but the recognition that such a law
dominates the entire universe, and that the world is nothing else than
an eternal "evolution of substance," is a fruit of the nineteenth
century. It was not until the second half of this century that it
attained to perfect clearness and a universal application. The immortal
merit of establishing the doctrine on an empirical basis, and pointing
out its world-wide application, belongs to the great scientist Charles
Darwin; he it was who, in 1859, supplied a solid foundation for the
theory of descent, which the able French naturalist Jean Lamarck had
already sketched in its broad outlines in 1809, and the fundamental
idea of which had been almost prophetically enunciated in 1799 by
Germany's greatest poet and thinker, Wolfgang Goethe. In that theory we
have the key to "the question of all questions," to the great enigma
of "the place of man in nature," and of his natural development. If we
are in a position to-day to recognize the sovereignty of the law of
evolution--and, indeed, of a monistic evolution--in every province of
nature, and to use it, in conjunction with the law of substance, for a
simple interpretation of all natural phenomena, we owe it chiefly to
those three distinguished naturalists; they shine as three stars of the
first magnitude amid all the great men of the century.

This marvellous progress in a theoretical knowledge of nature has
been followed by a manifold practical application in every branch
of civilized life. If we are to-day in the "age of commerce," if
international trade and communication have attained dimensions beyond
the conception of any previous age, if we have transcended the limits
of space and time by our telegraph and telephone, we owe it, in the
first place, to the technical advancement of physics, especially in
the application of steam and electricity. If, in photography, we can,
with the utmost ease, compel the sunbeam to create for us in a moment's
time a correct picture of any object we like; if we have made enormous
progress in agriculture, and in a variety of other pursuits; if, in
surgery, we have brought an infinite relief to human pain by our
chloroform and morphia, our antiseptics and serous therapeutics, we
owe it all to applied chemistry. But it is so well known how much we
have surpassed all earlier centuries through these and other scientific
discoveries that we need linger over the question no longer.

While we look back with a just pride on the immense progress of the
nineteenth century in a knowledge of nature and in its practical
application, we find, unfortunately, a very different and far from
agreeable picture when we turn to another and not less important
province of modern life. To our great regret we must endorse the words
of Alfred Wallace: "Compared with our astounding progress in physical
science and its practical application, our system of government, of
administrative justice, and of national education, and our entire
social and moral organization, remain in a state of barbarism." To
convince ourselves of the truth of this grave indictment we need only
cast an unprejudiced glance at our public life, or look into the mirror
that is daily offered to us by the press, the organ of public sentiment.

We begin our review with justice, the _fundamentum regnorum_. No one
can maintain that its condition to-day is in harmony with our advanced
knowledge of man and the world. Not a week passes in which we do not
read of judicial decisions over which every thoughtful man shakes his
head in despair; many of the decisions of our higher and lower courts
are simply unintelligible. We are not referring in the treatment of
this particular "world-problem" to the fact that many modern states, in
spite of their paper constitutions, are really governed with absolute
despotism, and that many who occupy the bench give judgment less in
accordance with their sincere conviction than with wishes expressed
in higher quarters. We readily admit that the majority of judges and
counsel decide conscientiously, and err simply from human frailty.
Most of their errors, indeed, are due to defective preparation. It is
popularly supposed that these are just the men of highest education,
and that on that very account they have the preference in nominations
to different offices. However, this famed "legal education" is for the
most part rather of a formal and technical character. They have but a
superficial acquaintance with that chief and peculiar object of their
activity, the human organism, and its most important function, the
mind. That is evident from the curious views as to the liberty of the
will, responsibility, etc., which we encounter daily. I once told an
eminent jurist that the tiny spherical ovum from which every man is
developed is as truly endowed with life as the embryo of two, or seven,
or even nine months; he laughed incredulously. Most of the students
of jurisprudence have no acquaintance with anthropology, psychology,
and the doctrine of evolution--the very first requisites for a correct
estimate of human nature. They have "no time" for it; their time is
already too largely bespoken for an exhaustive study of beer and wine
and for the noble art of fencing. The rest of their valuable study-time
is required for the purpose of learning some hundreds of paragraphs of
law books, a knowledge of which is supposed to qualify the jurist for
any position whatever in our modern civilized community.

We shall touch but lightly on the unfortunate province of politics, for
the unsatisfactory condition of the modern political world is only too
familiar. In a great measure its evils are due to the fact that most of
our officials are jurists--that is, men of high technical education,
but utterly devoid of that thorough knowledge of human nature which is
only obtained by the study of comparative anthropology and the monistic
psychology--men without an acquaintance with those social relations of
which we find the earlier types in comparative zoology and the theory
of evolution, in the cellular theory, and the study of the protists. We
can only arrive at a correct knowledge of the structure and life of the
social body, the state, through a scientific knowledge of the structure
and life of the individuals who compose it, and the cells of which they
are in turn composed. If our political rulers and our "representatives
of the people" possessed this invaluable biological and anthropological
knowledge, we should not find our journals so full of the sociological
blunders and political nonsense which at present are far from adorning
our parliamentary reports, and even many of our official documents.
Worst of all is it when the modern state flings itself into the arms
of the reactionary Church, and when the narrow-minded self-interest
of parties and the infatuation of short-sighted party-leaders lend
their support to the hierarchy. Then are witnessed such sad scenes
as the German Reichstag puts before our eyes even at the close of
the nineteenth century. We have the spectacle of the educated German
people in the power of the ultramontane Centre, under the rule of the
Roman papacy, which is its bitterest and most dangerous enemy. Then
superstition and stupidity reign instead of right and reason. Never
will our government improve until it casts off the fetters of the
Church and raises the views of the citizens on man and the world to a
higher level by a general scientific education. That does not raise
the question of any special form of constitution. Whether a monarchy
or a republic be preferable, whether the constitution should be
aristocratic or democratic, are subordinate questions in comparison
with the supreme question: Shall the modern civilized state be
spiritual or secular? Shall it be _theocratic_--ruled by the irrational
formulæ of faith and by clerical despotism--or _nomocratic_--under the
sovereignty of rational laws and civic right? The first task is to
kindle a rational interest in our youth, and to uplift our citizens
and free them from superstition. That can only be achieved by a timely
reform of our schools.

Our education of the young is no more in harmony with modern scientific
progress than our legal and political world. Physical science, which
is so much more important than all other sciences, and which, properly
understood, really embraces all the so-called moral sciences, is still
regarded as a mere accessory in our schools, if not treated as the
Cinderella of the curriculum. Most of our teachers still give the
most prominent place to that dead learning which has come down from
the cloistral schools of the Middle Ages. In the front rank we have
grammatical gymnastics and an immense waste of time over a "thorough
knowledge" of classics and of the history of foreign nations. Ethics,
the most important object of practical philosophy, is entirely
neglected, and its place is usurped by the ecclesiastical creed. Faith
must take precedence over knowledge--not that scientific faith which
leads to a monistic religion, but the irrational superstition that
lays the foundation of a perverted Christianity. The valuable teaching
of modern cosmology and anthropology, of biology and evolution, is
most inadequately imparted, if not entirely unknown, in our higher
schools; while the memory is burdened with a mass of philological and
historical facts which are utterly useless, either from the point of
view of theoretical education or for the practical purposes of life.
Moreover, the antiquated arrangements and the distribution of faculties
in the universities are just as little in harmony with the point we
have reached in monistic science as the curriculum of the primary and
secondary schools.

The climax of the opposition to modern education and its foundation,
advanced natural philosophy, is reached, of course, in the Church. We
are not speaking here of ultramontane papistry, nor of the orthodox
evangelical tendencies, which do not fall far short of it in ignorance
and in the crass superstition of their dogmas. We are imagining
ourselves for the moment to be in the church of a liberal Protestant
minister, who has a good average education, and who finds room for
"the rights of reason" by the side of his faith. There, besides
excellent moral teaching, which is in perfect harmony with our own
monistic ethics, and humanitarian discussion of which we cordially
approve, we hear ideas on the nature of God, of the world, of man, and
of life which are directly opposed to all scientific experience. It
is no wonder that physicists and chemists, doctors and philosophers,
who have made a thorough study of nature, refuse a hearing to such
preachers. Our theologians and our politicians are just as ignorant
as our philosophers and our jurists of that elementary knowledge of
nature which is based on the monistic theory of evolution, and which is
already far exceeded in the triumph of our modern learning.

From this opposition, which we can only briefly point out at present,
there arise grave conflicts in our modern life which urgently demand
a settlement. Our modern education, the outcome of our great advance
in knowledge, has a claim upon every department of public and private
life; it would see humanity raised, by the instrumentality of
reason, to that higher grade of culture, and, consequently, to that
better path towards happiness which has been opened out to us by the
progress of modern science. That aim, however, is vigorously opposed
by the influential parties who would detain the mind in the exploded
views of the Middle Ages with regard to the most important problems
of life; they linger in the fold of traditional dogma, and would
have reason prostrate itself before their "higher revelation." That
is the condition of things, to a very large extent, in theology and
philosophy, in sociology and jurisprudence. It is not that the motives
of the latter are to be attributed, as a rule, to pure self-interest;
they spring partly from ignorance of the facts, and partly from an
indolent acquiescence in tradition. The most dangerous of the three
great enemies of reason and knowledge is not malice; but ignorance, or,
perhaps, indolence. The gods themselves still strive in vain against
these two latter influences when they have happily vanquished the first.

One of the main supports of that reactionary system is still what
we may call "anthropism." I designate by this term "that powerful
and world-wide group of erroneous opinions which opposes the human
organism to the whole of the rest of nature, and represents it to be
the preordained end of the organic creation, an entity essentially
distinct from it, a godlike being." Closer examination of this group of
ideas shows it to be made up of three different dogmas, which we may
distinguish as the _anthropocentric_, the _anthropomorphic_, and the

I. The _anthropocentric_ dogma culminates in the idea that man
is the preordained centre and aim of all terrestrial life--or, in
a wider sense, of the whole universe. As this error is extremely
conducive to man's interest, and as it is intimately connected with the
creation-myth of the three great Mediterranean religions, and with the
dogmas of the Mosaic, Christian, and Mohammedan theologies, it still
dominates the greater part of the civilized world.

II. The _anthropomorphic_ dogma is likewise connected with the
creation-myth of the three aforesaid religions, and of many others. It
likens the creation and control of the world by God to the artificial
creation of a talented engineer or mechanic, and to the administration
of a wise ruler. God, as creator, sustainer, and ruler of the world,
is thus represented after a purely human fashion in his thought and
work. Hence it follows, in turn, that man is godlike. "God made man
to His own image and likeness." The older, naïve mythology is pure
"homotheism," attributing human shape, flesh, and blood to the gods.
It is more intelligible than the modern mystic theosophy that adores
a personal God as an invisible--properly speaking, gaseous--being,
yet makes him think, speak, and act in human fashion; it gives us the
paradoxical picture of a "gaseous vertebrate."

III. The _anthropolatric_ dogma naturally results from this comparison
of the activity of God and man; it ends in the apotheosis of the human
organism. A further result is the belief in the personal immortality of
the soul, and the dualistic dogma of the twofold nature of man, whose
"immortal soul" is conceived as but the temporary inhabitant of the
mortal frame. Thus these three anthropistic dogmas, variously adapted
to the respective professions of the different religions, came at
length to be vested with an extraordinary importance, and proved the
source of the most dangerous errors. The anthropistic view of the world
which springs from them is in irreconcilable opposition to our monistic
system; indeed, it is at once disproved by our new cosmological

Not only the three anthropistic dogmas, but many other notions of the
dualistic philosophy and orthodox religion, are found to be untenable
as soon as we regard them critically from the cosmological perspective
of our monistic system. We understand by that the comprehensive view
of the universe which we have from the highest point of our monistic
interpretation of nature. From that stand-point we see the truth of the
following "cosmological theorems," most of which, in our opinion, have
already been amply demonstrated:

(1) The universe, or the cosmos, is eternal, infinite, and illimitable.
(2) Its substance, with its two attributes (matter and energy), fills
infinite space, and is in eternal motion. (3) This motion runs on
through infinite time as an unbroken development, with a periodic
change from life to death, from evolution to devolution. (4) The
innumerable bodies which are scattered about the space-filling ether
all obey the same "law of substance;" while the rotating masses slowly
move towards their destruction and dissolution in one part of space
others are springing into new life and development in other quarters
of the universe. (5) Our sun is one of these unnumbered perishable
bodies, and our earth is one of the countless transitory planets that
encircle them. (6) Our earth has gone through a long process of cooling
before water, in liquid form (the first condition of organic life),
could settle thereon. (7) The ensuing biogenetic process, the slow
development and transformation of countless organic forms, must have
taken many millions of years--considerably over a hundred.[5] (8) Among
the different kinds of animals which arose in the later stages of the
biogenetic process on earth the vertebrates have far outstripped all
other competitors in the evolutionary race. (9) The most important
branch of the vertebrates, the mammals, were developed later (during
the triassic period) from the lower amphibia and the reptilia. (10) The
most perfect and most highly developed branch of the class mammalia is
the order of primates, which first put in an appearance, by development
from the lowest prochoriata, at the beginning of the Tertiary
period--at least three million years ago. (11) The youngest and most
perfect twig of the branch primates is man, who sprang from a series of
manlike apes towards the end of the Tertiary period. (12) Consequently,
the so-called "history of the world"--that is, the brief period of a
few thousand years which measures the duration of civilization--is an
evanescently short episode in the long course of organic evolution,
just as this, in turn, is merely a small portion of the history of
our planetary system; and as our mother-earth is a mere speck in the
sunbeam in the illimitable universe, so man himself is but a tiny grain
of protoplasm in the perishable framework of organic nature.

Nothing seems to me better adapted than this magnificent cosmological
perspective to give us the proper standard and the broad outlook
which we need in the solution of the vast enigmas that surround us.
It not only clearly indicates the true place of man in nature, but it
dissipates the prevalent illusion of man's supreme importance, and
the arrogance with which he sets himself apart from the illimitable
universe, and exalts himself to the position of its most valuable
element. This boundless presumption of conceited man has misled him
into making himself "the image of God," claiming an "eternal life" for
his ephemeral personality, and imagining that he possesses unlimited
"freedom of will." The ridiculous imperial folly of Caligula is but
a special form of man's arrogant assumption of divinity. Only when
we have abandoned this untenable illusion, and taken up the correct
cosmological perspective, can we hope to reach the solution of the
"riddles of the universe."

The uneducated member of a civilized community is surrounded with
countless enigmas at every step, just as truly as the savage. Their
number, however, decreases with every stride of civilization and of
science; and the monistic philosophy is ultimately confronted with but
one simple and comprehensive enigma--the "problem of substance." Still,
we may find it useful to include a certain number of problems under
that title. In the famous speech which Emil du Bois-Reymond delivered
in 1880, in the Leibnitz session of the Berlin Academy of Sciences,
he distinguished seven world-enigmas, which he enumerated as follows:
(1) The nature of matter and force. (2) The origin of motion. (3) The
origin of life. (4) The (apparently preordained) orderly arrangement
of nature. (5) The origin of simple sensation and consciousness. (6)
Rational thought, and the origin of the cognate faculty, speech. (7)
The question of the freedom of the will. Three of these seven enigmas
are considered by the orator of the Berlin Academy to be entirely
transcendental and insoluble--they are the first, second, and fifth;
three others (the third, fourth, and sixth) he considers to be capable
of solution, though extremely difficult; as to the seventh and last
"world-enigma," the freedom of the will, which is the one of the
greatest practical importance, he remains undecided.

As my monism differs materially from that of the Berlin orator, and as
his idea of the "seven great enigmas" has been very widely accepted,
it may be useful to indicate their true position at once. In my
opinion, the three transcendental problems (1, 2, and 5) are settled
by our conception of substance (_vide_ chap. xii.); the three which
he considers difficult, though soluble, (3, 4, and 6), are decisively
answered by our modern theory of evolution; the seventh and last, the
freedom of the will, is not an object for critical, scientific inquiry
at all, for it is a pure dogma, based on an illusion, and has no real

The means and methods we have chosen for attaining the solution of the
great enigma do not differ, on the whole, from those of all purely
scientific investigation--firstly, experience; secondly, inference.
Scientific experience comes to us by observation and experiment, which
involve the activity of our sense-organs in the first place, and,
secondly, of the inner sense-centres in the cortex of the brain. The
microscopic elementary organs of the former are the sense-cells; of the
latter, groups of ganglionic cells. The experiences which we derive
from the outer world by these invaluable instruments of our mental life
are then moulded into ideas by other parts of the brain, and these,
in their turn, are united in a chain of reasoning by association. The
construction of this chain may take place in two different ways, which
are, in my opinion, equally valuable and indispensable: _induction_
and _deduction_. The higher cerebral operations, the construction
of complicated chains of reasoning, abstraction, the formation of
concepts, the completion of the perceptive faculty by the plastic
faculty of the imagination--in a word, consciousness, thought, and
speculation--are functions of the ganglionic cells of the cortex of the
brain, just like the preceding simpler mental functions. We unite them
all in the supreme concept of _reason_.[6]

By reason only can we attain to a correct knowledge of the world and a
solution of its great problems. Reason is man's highest gift, the only
prerogative that essentially distinguishes him from the lower animals.
Nevertheless, it has only reached this high position by the progress of
culture and education, by the development of knowledge. The uneducated
man and the savage are just as little (or just as much) "rational"
as our nearest relatives among the mammals (apes, dogs, elephants,
etc.). Yet the opinion still obtains in many quarters that, besides
our godlike reason, we have two further (and even surer!) methods of
receiving knowledge--emotion and revelation. We must at once dispose
of this dangerous error. Emotion has nothing whatever to do with the
attainment of truth. That which we prize under the name of "emotion"
is an elaborate activity of the brain, which consists of feelings of
like and dislike, motions of assent and dissent, impulses of desire and
aversion. It may be influenced by the most diverse activities of the
organism, by the cravings of the senses and the muscles, the stomach,
the sexual organs, etc. The interests of truth are far from promoted
by these conditions and vacillations of emotion; on the contrary, such
circumstances often disturb that reason which alone is adapted to the
pursuit of truth, and frequently mar its perceptive power. No cosmic
problem is solved, or even advanced, by the cerebral function we call
emotion. And the same must be said of the so-called "revelation," and
of the "truths of faith" which it is supposed to communicate; they are
based entirely on a deception, consciously or unconsciously, as we
shall see in the sixteenth chapter.

We must welcome as one of the most fortunate steps in the direction
of a solution of the great cosmic problems the fact that of recent
years there is a growing tendency to recognize the two paths which
alone lead thereto--_experience_ and _thought_, or _speculation_--to
be of equal value, and mutually complementary. Philosophers have come
to see that pure speculation--such, for instance, as Plato and Hegel
employed for the construction of their _idealist_ systems--does not
lead to knowledge of reality. On the other hand, scientists have been
convinced that mere experience--such as Bacon and Mill, for example,
made the basis of their _realist_ systems--is insufficient of itself
for a complete philosophy. For these two great paths of knowledge,
sense-experience and rational thought, are two distinct cerebral
functions; the one is elaborated by the sense-organs and the inner
sense-centres, the other by the thought-centres, the great "centres
of association in the cortex of the brain," which lie between the
sense-centres. (Cf. cc. vii. and x.) True knowledge is only acquired
by combining the activity of the two. Nevertheless, there are still
many philosophers who would construct the world out of their own
inner consciousness, and who reject our empirical science precisely
because they have no knowledge of the real world. On the other hand,
there are many scientists who still contend that the sole object of
science is "the knowledge of facts, the objective investigation of
isolated phenomena"; that "the age of philosophy" is past, and science
has taken its place.[7] This one-sided over-estimation of experience
is as dangerous an error as the converse exaggeration of the value of
speculation. Both channels of knowledge are mutually indispensable.
The greatest triumphs of modern science--the cellular theory, the
dynamic theory of heat, the theory of evolution, and the law of
substance--are _philosophic achievements_; not, however, the fruit of
pure speculation, but of an antecedent experience of the widest and
most searching character.

At the commencement of the nineteenth century the great idealistic
poet, Schiller, gave his counsel to both groups of combatants, the
philosophers and the scientists:

    "Does strife divide your efforts--no union bless your toil?
    Will truth e'er be delivered if ye your forces rend?"

Since then the situation has, happily, been profoundly modified; while
both schools, in their different paths, have pressed onward towards the
same high goal, they have recognized their common aspiration, and they
draw nearer to a knowledge of the truth in mutual covenant. At the end
of the nineteenth century we have returned to that monistic attitude
which our greatest realistic poet, Goethe, had recognized from its very
commencement to be alone correct and fruitful.[8]

All the different philosophical tendencies may, from the point of
view of modern science, be ranged in two antagonistic groups; they
represent either a _dualistic_ or a _monistic_ interpretation of
the cosmos. The former is usually bound up with teleological and
idealistic dogmas, the latter with mechanical and realistic theories.
Dualism, in the widest sense, breaks up the universe into two entirely
distinct substances--the material world and an immaterial God, who
is represented to be its creator, sustainer, and ruler. Monism, on
the contrary (likewise taken in its widest sense), recognizes one
sole substance in the universe, which is at once "God and nature";
body and spirit (or matter and energy) it holds to be inseparable.
The extramundane God of dualism leads necessarily to theism; and the
intra-mundane God of the monist leads to pantheism.

The different ideas of _monism_ and _materialism_, and likewise
the essentially distinct tendencies of theoretical and practical
materialism, are still very frequently confused. As this and other
similar cases of confusion of ideas are very prejudicial, and give rise
to innumerable errors, we shall make the following brief observations,
in order to prevent misunderstanding:

I. Pure monism is identical neither with the theoretical materialism
that denies the existence of spirit, and dissolves the world into a
heap of dead atoms, nor with the theoretical spiritualism (lately
entitled "energetic" spiritualism by Ostwald) which rejects the notion
of matter, and considers the world to be a specially arranged group of
"energies" or immaterial natural forces.

II. On the contrary, we hold, with Goethe, that "matter cannot exist
and be operative without spirit, nor spirit without matter." We
adhere firmly to the pure, unequivocal monism of Spinoza: Matter, or
infinitely extended substance, and spirit (or energy), or sensitive and
thinking substance, are the two fundamental attributes or principal
properties of the all-embracing divine essence of the world, the
universal substance. (Cf. chap. xii.)



    Fundamental Importance of Anatomy--Human Anatomy--Hippocrates,
    Aristotle, Galen, Vesalius--Comparative Anatomy--Georges
    Cuvier--Johannes Müller--Karl Gegenbaur--Histology--The Cellular
    Theory--Schleiden and Schwann--Kölliker--Virchow--Man a
    Vertebrate, a Tetrapod, a Mammal, a Placental, a Primate--Prosimiæ
    and Simiæ--The Catarrhinæ--Papiomorphic and Anthropomorphic
    Apes--Essential Likeness of Man and the Ape in Corporal Structure

All biological research, all investigation into the forms and vital
activities of organisms, must first deal with the visible body, in
which the morphological and physiological phenomena are observed. This
fundamental rule holds good for man just as much as for all other
living things. Moreover, the inquiry must not confine itself to mere
observation of the outer form; it must penetrate to the interior, and
study both the general plan and the minute details of the structure.
The science which pursues this fundamental investigation in the
broadest sense is anatomy.

The first stimulus to an inquiry into the human frame arose, naturally,
in medicine. As it was usually practised by the priests in the older
civilizations, we may assume that these highest representatives of
the education of the time had already acquired a certain amount
of anatomical knowledge two thousand years before Christ, or even
earlier. We do not, however, find more exact observations, founded
on the dissection of mammals, and applied, by analogy, to the human
frame, until we come to the Greek scientists of the sixth and fifth
centuries before Christ--Empedocles (of Agrigentum) and Democritus
(of Abdera), and especially the most famous physician of classic
antiquity, Hippocrates (of Cos). It was from these and other sources
that the great Aristotle, the renowned "father of natural history,"
equally comprehensive as investigator and philosopher, derived his
first knowledge. After him only one anatomist of any consequence is
found in antiquity, the Greek physician Claudius Galenus (of Pergamus),
who developed a wealthy practice in Rome in the second century after
Christ, under the Emperor Marcus Aurelius. All these ancient anatomists
acquired their knowledge, as a rule, not by the dissection of the human
body itself--which was then sternly forbidden--but by a study of the
bodies of the animals which most closely resembled man, especially the
apes; they were all, indeed, comparative anatomists.

The triumph of Christianity and its mystic theories meant retrogression
to anatomy, as it did to all the other sciences. The popes were
resolved above all things to detain humanity in ignorance; they rightly
deemed a knowledge of the human organism to be a dangerous source
of enlightenment as to our true nature. During the long period of
thirteen centuries the writings of Galen were almost the only source
of human anatomy, just as the works of Aristotle were for the whole
of natural history. It was not until the sixteenth century, when the
spiritual tyranny of the papacy was broken by the Reformation, and the
geocentric theory, so intimately connected with papal doctrine, was
destroyed by the new cosmic system of Copernicus, that the knowledge
of the human frame entered upon a new period of progress. The great
anatomists, Vesalius (of Brussels), and Eustachius and Fallopius
(of Modena), advanced the knowledge of our bodily structure so much
by their own thorough investigations that little remained for their
numerous followers to do, with regard to the more obvious phenomena,
except the substantiation of details. Andreas Vesalius, as courageous
as he was talented and indefatigable, was the pioneer of the movement;
he completed in his twenty-eighth year (1543) that great and systematic
work _De humani corporis fabrica_; he gave to the whole of human
anatomy a new and independent scope and a more solid foundation. On
that account he was, at a later date, at Madrid--where he was physician
to Charles V. and Philip II.--condemned to death by the Inquisition as
a magician. He only escaped by undertaking a pilgrimage to Jerusalem;
in returning he suffered shipwreck on the Isle of Zante, and died there
in misery and destitution.

The great merit of the nineteenth century, as far as our knowledge of
the human frame is concerned, lies in the founding of two new lines
of research of immense importance--comparative anatomy and histology,
or microscopic anatomy. The former was intimately associated with
human anatomy from the very beginning; indeed, it had to supply the
place of the latter so long because the dissection of human corpses
was a crime visited with capital punishment--that was the case even
in the fifteenth century! But the many anatomists of the next three
centuries devoted themselves mainly to a more accurate study of the
human organism. The elaborate science which we now call comparative
anatomy was born in the year 1803, when the great French zoologist
Georges Cuvier (a native of Mömpelgard, in Alsace) published his
profound _Leçons sur l'anatomie comparée_, and endeavored to formulate,
for the first time, definite laws as to the organism of man and the
beasts. While his predecessors--among whom was Goethe in 1790--had
mainly contented themselves with comparing the skeleton of man with
those of other animals, Cuvier's broader vision took in the whole
of the animal organization. He distinguished therein four great and
mutually independent types: Vertebrata, Articulata, Mollusca, and
Radiata. This advance was of extreme consequence for our "question
of all questions," since it clearly brought out the fact that man
belonged to the vertebral type, and differed fundamentally from all
the other types. It is true that the keen-sighted Linné had already,
in his _Systema Natuae_, made a great step in advance by assigning
man a definite place in the class of mammals; he had even drawn up
the three groups of half-apes, apes, and men (_Lemur_, _simia_, and
_homo_) in the order of primates. But his keen, systematic mind was
not furnished with that profound empirical foundation, supplied by
comparative anatomy, which Cuvier was the first to attain. Further
developments were added by the great comparative anatomists of our own
century--Friedrich Meckel (Halle), Johannes Müller (Berlin), Richard
Owen, T. Huxley, and Karl Gegenbaur (Jena, subsequently Heidelberg).
The last-named, in applying the evolutionary theory, which Darwin had
just established, to comparative anatomy, raised his science to the
front rank of biological studies. The numerous comparative anatomical
works of Gegenbaur are, like his well-known _Manual of Human Anatomy_,
equally distinguished by a thorough empirical acquaintance with their
immense multitudes of facts, and by a comprehensive control of his
material, and its philosophic appreciation in the evolutionary sense.
His recent _Comparative Anatomy of the Vertebrata_ establishes the
solid foundation on which our conviction of the vertebral character of
man in every aspect is chiefly based.

Microscopic anatomy has been developed, in the course of the present
century, in a very different fashion from comparative anatomy. At
the beginning of the century (1802) a French physician, Bichat, made
an attempt to dissect the organs of the human body into their finer
constituents by the aid of the microscope, and to show the connection
of these various _tissues_ (_hista_, or _tela_). This first attempt
led to little result, because the scientist was ignorant of the one
common element of all the different tissues. This was first discovered
(1838) in the shape of the _cell_, in the plant world, by Matthias
Schleiden, and immediately afterwards proved to be the same in the
animal world by Theodor Schwann, the pupil and assistant of Johannes
Müller at Berlin. Two other distinguished pupils of this great master,
who are still living, Albert Kölliker and Rudolph Virchow, took up
the cellular theory, and the theory of tissues which is founded on
it, in the sixties, and applied them to the human organism in all its
details, both in health and disease; they proved that, in man and
all other animals, every tissue is made up of the same microscopic
particles, the _cells_, and these "elementary organisms" are the real,
self-active citizens which, in combinations of millions, constitute
the "cellular state," our body. All these cells spring from one simple
cell, the _cytula_, or impregnated ovum, by continuous subdivision.
The general structure and combination of the tissues are the same in
man as in the other vertebrates. Among these the mammals, the youngest
and most highly developed class take precedence, in virtue of certain
special features which were acquired late. Such are, for instance, the
microscopic texture of the hair, of the glands of the skin, and of the
breasts, and the corpuscles of the blood, which are quite peculiar to
mammals, and different from those of the other vertebrates; man, even
in these finest histological relations, is a _true mammal_.

The microscopic researches of Albert Kölliker and Franz Leydig (at
Würzburg) not only enlarged our knowledge of the finer structure of man
and the beasts in every direction, but they were especially important
in the light of their connection with the evolution of the cell and
the tissue; they confirmed the great theory of Carl Theodor Siebold
(1845) that the lowest animals, the Infusoria and the Rhizopods, are
unicellular organisms.

Our whole frame, both in its general plan and its detailed structure,
presents the characteristic type of the vertebrates. This most
important and most highly developed group in the animal world was
first recognized in its natural unity in 1801 by the great Lamarck;
he embraced under that title the four higher animal groups of
Linné--mammals, birds, amphibia, and fishes. To these he opposed the
two lower classes, insects and worms, as invertebrates. Cuvier (1812)
established the unity of the vertebrate type on a firmer basis by
his comparative anatomy. It is quite true that all the vertebrates,
from the fish up to man, agree in every essential feature; they all
have a firm internal skeleton, a framework of cartilage and bone,
consisting principally of a vertebral column and a skull; the advanced
construction of the latter presents many variations, but, on the whole,
all may be reduced to the same fundamental type. Further, in all
vertebrates the "organ of the mind," the central nervous system, in
the shape of a spinal cord and a brain, lies at the back of this axial
skeleton. Moreover, what we said of its bony environment, the skull,
is also true of the brain--the instrument of consciousness and all the
higher functions of the mind; its construction and size present very
many variations in detail, but its general characteristic structure
remains always the same.

We meet the same phenomenon when we compare the rest of our organs with
those of the other vertebrates; everywhere, in virtue of heredity,
the original plan and the relative distribution of the organs remain
the same, although, through adaptation to different environments,
the size and the structure of particular sections offer considerable
variation. Thus we find that in all cases the blood circulates in
two main blood-vessels, of which one--the aorta--passes over the
intestine, and the other--the principal vein--passes underneath, and
that by the broadening out of the latter in a very definite spot a
heart has arisen; this "ventral heart" is just as characteristic of all
vertebrates as the "dorsal heart" is of the articulata and mollusca.
Equally characteristic of all vertebrates is the early division of
the intestinal tube into a "head-gut" (or gill-gut), which serves in
respiration, and a "body-gut" (or liver-gut), which co-operates with
the liver in digestion; so are, likewise, the ramification of the
muscular system, the peculiar structure of the urinary and sexual
organs, and so forth. In all these anatomical relations _man is a true

Aristotle gave the name of four-footed, or tetrapoda, to all the higher
warm-blooded animals which are distinguished by the possession of two
pairs of legs. The category was enlarged subsequently, and its title
changed into the Latin "quadrupeda," when Cuvier proved that even
"two-legged" birds and men are really "four-footed"; he showed that the
internal skeleton of the four legs in all the higher land-vertebrates,
from the amphibia up to man, was originally constructed after the same
pattern out of a definite number of members. The "arm" of man and the
"wing" of bats and birds have the same typical skeleton as the foreleg
of the animals which are conspicuously "four-footed."

The anatomical unity of the fully developed skeleton in the four limbs
of all tetrapods is very important. In order to appreciate it fully
one has only to compare carefully the skeleton of a salamander or a
frog with that of a monkey or a man. One perceives at once that the
humeral zone in front and the pelvic zone behind are made up of the
same principal parts as in the rest of the quadrupeds. We find in all
cases that the first section of the leg proper consists of one strong
marrow-bone (the _humerus_, in the forearm; the _femur_, behind);
the second part, on the contrary, originally always consists of two
bones (the _ulna_ and _radius_, in front; the _fibula_ and _tibia_,
behind). When we further compare the developed structure of the foot
proper we are surprised to find that the small bones of which it is
made up are also similarly arranged and distributed in every case: in
the front limb the three groups of bones of the forefoot (or "hand")
correspond in all classes of the tetrapoda: (1) the _carpus_, (2)
the _metacarpus_, (3) the five fingers (_digiti anteriores_); in the
rear limb, similarly, we have always the same three osseous groups of
the hind foot: (1) the _tarsus_, (2) the _metatarsus_, and (3) the
five toes (_digiti posteriores_). It was a very difficult task to
reduce all these little bones to one primitive type, and to establish
the equivalence (or homology) of the separate parts in all cases;
they present extreme variations of form and construction in detail,
sometimes being partly fused together and losing their individuality.
This great task was first successfully achieved by the most eminent
comparative anatomist of our day, Karl Gegenbaur. He pointed out,
in his _Researches into the Comparative Anatomy of the Vertebrata_
(1864), how this characteristic "five-toed leg" of the land tetrapods
originally (not before the Carboniferous period) arose out of the
radiating fin (the breast-fin, or the belly-fin) of the ancient
fishes. He had also, in his famous _Researches into the Skull of the
Vertebrata_ (1872), deduced the younger skull of the tetrapods from the
oldest cranial form among the fishes, that of the shark.

It is especially remarkable that the original number of the toes (five)
on each of the four feet, which first appeared in the old amphibia
of the Carboniferous period, has, in virtue of a strict heredity,
been preserved even to the present day in man. Also, naturally and
harmoniously, the typical construction of the joints, ligaments,
muscles, and nerves of the two pairs of legs has, in the main, remained
the same as in the rest of the "four-footed." In all these important
relations _man is a true tetrapod_.

The mammals are the youngest and most advanced class of the vertebrates.
It is true they are derived from the older class of amphibia, like
birds and reptiles: yet they are distinguished from all the other
tetrapods by a number of very striking anatomical features. Externally,
there is the clothing of the skin with hair, and the possession of
two kinds of skin glands--the sweat glands and the sebaceous glands.
A local development of these glands on the abdominal skin gave
rise (probably during the Triassic period) to the organ which is
especially characteristic of the class, and from which it derives its
name--the _mammarium_. This important instrument of lactation is made
up of milk glands (_mammae_) and the "mammar-pouches" (folds of the
abdominal skin); in its development the teats appear, through which
the young mammal sucks its mother's milk. In internal structure the
most remarkable feature is the possession of a complete diaphragm, a
muscular wall which, in all mammals--and _only_ in mammals--separates
the thoracic from the abdominal cavity; in all other vertebrates
there is no such separation. The skull of mammals is distinguished
by a number of remarkable formations, especially in the maxillary
apparatus (the upper and lower jaws, and the temporal bones). Moreover,
the brain, the olfactory organ, the heart, the lungs, the internal
and external sexual organs, the kidneys, and other parts of the body
present special peculiarities, both in general and detailed structure,
in the mammals; all these, taken collectively, point unequivocally
to an early derivation of the mammals from the older groups of the
reptiles and amphibia, which must have taken place, at the latest, in
the Triassic period--at least twelve million years ago! In all these
important characteristics _man is a true mammal_.

The numerous orders (12-33) which modern systematic zoology
distinguishes in the class of mammals had been arranged in 1816
(by Blainville) in three natural groups, which still hold good as
sub-classes: (1) the monotrema, (2) the marsupialia, and (3) the
placentalia. These three sub-classes not only differ in the important
respect of bodily structure and development, but they correspond, also,
to three different historical stages in the formation of the class,
as we shall see later on. The monotremes of the Triassic period were
followed by the marsupials of the Jurassic, and these by the placentals
of the Cretaceous. Man belongs to this, the youngest, sub-class; for
he presents in his organization all the features which distinguish
the placentals from the marsupials and the still older monotremes.
First of all, there is the peculiar organ which gives a name to the
placentals--the _placenta_. It serves the purpose of nourishing the
young mammal embryo for a long time during its enclosure in the
mother's womb; it consists of blood-bearing tufts which grow out of the
chorion surrounding the embryo, and penetrate corresponding cavities in
the mucous membrane of the maternal uterus; the delicate skin between
the two structures is so attenuated in this spot that the nutriment in
the mother's blood can pass directly into the blood of the child. This
excellent contrivance for nourishing the embryo, which makes its first
appearance at a somewhat late date, gives the foetus the opportunity
of a longer maintenance and a higher development in the protecting
womb; it is wanting in the _implacentalia_, the two older sub-classes
of the marsupials and the monotremes. There are, likewise, other
anatomical features, particularly the higher development of the brain
and the absence of the marsupial bone, which raise the placentals above
all their implacental ancestors. In all these important particulars
_man is a true placental_.

The very varied sub-class of the placentals has been recently
subdivided into a great number of orders; they are usually put at from
ten to sixteen, but when we include the important extinct forms which
have been recently discovered the number runs up to from twenty to
twenty-six. In order to facilitate the study of these numerous orders,
and to obtain a deeper insight into their kindred construction, it
is very useful to form them into great natural groups, which I have
called "legions." In my latest attempt[9] to arrange the advanced
system of placentals in phylogenetic order I have substituted eight
of these legions for the twenty-six orders, and shown that these may
be reduced to four main groups. These, in turn, are traceable to one
common ancestral group of all the placentals, their fossil ancestors,
the _prochoriata_ of the Cretaceous period. These are directly
connected with the marsupial ancestors of the Jurassic period. We
will only specify here, as the most important living representatives
of these four main groups, the rodentia, the ungulata, the carnivora,
and the primates. To the legion of the primates belong the prosimiæ
(half-apes), the simiæ (real apes), and man. All the members of these
three orders agree in many important features, and are at the same
time distinguished by these features from the other twenty-three
orders of placentals. They are especially conspicuous for the length
of their bones, which were originally adapted to their arboreal manner
of life. Their hands and feet are five-fingered, and the long fingers
are excellently suited for grasping and embracing the branches of
trees; they are provided, either partially or completely, with nails,
but have no claws. The dentition is complete, containing all four
classes--incisors, canine, premolars, and molars. Primates are also
distinguished from all the other placentals by important features in
the special construction of the skull and the brain; and these are the
more striking in proportion to their development and the lateness of
their appearance in the history of the earth. In all these important
anatomical features our human organism agrees with that of all the
other primates: _man is a true primate_.

An impartial and thorough comparison of the bodily structure of the
primates forces us to distinguish two orders in this most advanced
legion of the mammalia--half-apes (_prosimiae_ or _hemipitheci_) and
apes (_simiae_ or _pitheci_). The former seem in every respect to be
the lower and older, the latter to be the higher and younger order. The
womb of the half-ape is still double, or two-horned, as it is in all
the other mammals. In the true ape, on the contrary, the right and left
wombs have completely amalgamated; they blend into a pear-shaped womb,
which the human mother possesses besides the ape. In the skull of the
apes, just as in that of man, the orbits of the eyes are completely
separated from the temporal cavities by an osseous partition; in
the _prosimiae_ this is either entirely wanting or very imperfect.
Finally, the cerebrum of the _prosimia_ is either quite smooth or very
slightly furrowed, and proportionately small; that of the true ape is
much larger, and the gray bed especially, the organ of higher psychic
activity, is much more developed; the characteristic convolutions
and furrows appear on its surface exactly in proportion as the ape
approaches to man. In these and other important respects, particularly
in the construction of the face and the hands, _man presents all the
anatomical marks of a true ape_.

The extensive order of apes was divided by Geoffroi, in 1812, into
two sub-orders, which are still universally accepted in systematic
zoology--New World and Old World monkeys, according to the hemisphere
they respectively inhabit. The American "New World" monkeys are called
_Platyrrhinae_ (flat-nosed); their nose is flat, and the nostrils
divergent, with a broad partition. The "Old World" monkeys, on the
contrary, are called collectively _Catarrhinae_ (narrow-nosed); their
nostrils point downward, like man's, and the dividing cartilage is
narrow. A further difference between the two groups is that the
tympanum is superficial in the _platyrrhinae_, but lies deeper,
inside the petrous bone, in the _catarrhinae_; in the latter a long
and narrow bony passage has been formed, while in the former it is
still short and wide, or even altogether wanting. Finally, we have a
much more important and decisive difference between the two groups in
the circumstance that all the Old World monkeys have the same teeth
as man--_i. e._, twenty deciduous and thirty-two permanent teeth
(two incisors, one canine, two premolars, and three molars in each
half of the jaw). The New World monkeys, on the other hand, have an
additional premolar in each half-jaw, or thirty-six teeth altogether.
The fact that these anatomical differences of the two simian groups
are universal and conspicuous, and that they harmonize with their
geographical distribution in the two hemispheres, fully authorizes
a sharp systematic division of the two, as well as the phylogenetic
conclusion that for a very long period (for more than a million years)
the two sub-orders have been developing quite independently of each
other in the western and eastern hemispheres. That is a most important
point in view of the genealogy of our race; for man bears all the marks
of a _true catarrhina_; he has descended from some extinct member of
this sub-order in the Old World.

The numerous types of _catarrhinae_ which still survive in Asia and
Africa have been formed into two sections for some time--the tailed,
doglike apes (the _cynopitheci_) and the tailless, manlike apes (the
_anthropomorpha_). The latter are much nearer to man than the former,
not only in the absence of a tail and in the general build of the body
(especially of the head), but also on account of certain features
which are unimportant in themselves but very significant in their
constancy. The sacrum of the anthropoid ape, like that of man, is made
up of the fusion of five vertebræ; that of the _cynopithecus_ consists
of three (more rarely four) sacral vertebræ. The premolar teeth of
the _cynopitheci_ are greater in length than breadth; those of the
_anthropomorpha_ are broader than they are long; and the first molar
has four protuberances in the former, five in the latter. Furthermore,
the outer incisor of the lower jaw is broader than the inner one
in the manlike apes and man; in the doglike ape it is the smaller.
Finally, there is a special significance in the fact, established by
Selenka in 1890, that the anthropoid apes share with man the peculiar
structure of the discoid _placenta_, the _decidua reflexa_, and the
pedicle of the allantois. In fact, even a superficial comparison of
the bodily structure of the _anthropomorpha_ which still survive makes
it clear that both the Asiatic (the orang-outang and the gibbous ape)
and the African (the gorilla and chimpanzee) representatives of this
group are nearer to man in build than any of the _cynopitheci_. Under
the latter group we include the dog-faced papiomorpha, the baboon,
and the long-tailed monkey, at a very low stage. The anatomical
difference between these low papiomorpha and the most highly developed
anthropoid apes is greater in every respect, whatever organ we take
for comparison, than the difference between the latter and man.
This instructive fact was established with great penetration by the
anatomist Robert Hartmann, in his work on _The Anthropoid Apes_;[10]
he proposed to divide the order of _Simiae_ in a new way--namely, into
the two great groups of _primaria_ (man and the anthropoid ape) and the
_simiae_ proper, or _pitheci_ (the rest of the catarrhinæ and all the
platyrrhinæ). In any case, we have a clear proof of _the close affinity
of man and the anthropoid ape_.

Thus comparative anatomy proves to the satisfaction of every
unprejudiced and critical student the significant fact that the body of
man and that of the anthropoid ape are not only peculiarly similar, but
they are practically one and the same in every important respect. The
same two hundred bones, in the same order and structure, make up our
inner skeleton; the same three hundred muscles effect our movements;
the same hair clothes our skin; the same groups of ganglionic cells
build up the marvellous structure of our brain; the same four chambered
heart is the central pulsometer in our circulation; the same thirty-two
teeth are set in the same order in our jaws; the same salivary,
hepatic, and gastric glands compass our digestive process; the same
reproductive organs insure the maintenance of our race.

It is true that we find, on close examination, certain minor
differences in point of size and shape in most of the organs of man
and the ape; but we discover the same, or similar, differences
between the higher and lower races of men, when we make a careful
comparison--even, in fact, in a minute comparison of the various
individuals of our own race. We find no two persons who have exactly
the same size and form of nose, ears, eyes, and so forth. One has
only to compare attentively these special features in many different
persons in any large company to convince one's self of the astonishing
diversity of their construction and the infinite variability of
specific forms. Not infrequently even two sisters are so much unlike
as to make their origin from the same parents almost incredible. Yet
all these individual variations do not weaken the significance of the
fundamental similarity of structure; they are traceable to certain
minute differences in the growth of the individual features.



    Development of Physiology in Antiquity and the Middle Ages:
    Galen--Experiment and Vivisection--Discovery of the Circulation
    of the Blood by Harvey--Vitalism: Haller--Teleological and
    Vitalistic Conception of Life--Mechanical and Monistic View
    of the Physiological Processes--Comparative Physiology in the
    Nineteenth Century: Johannes Müller--Cellular Physiology: Max
    Verworn--Cellular Pathology: Virchow--Mammal Physiology--Similarity
    of all Vital Activity in Man and the Ape

It is only in the nineteenth century that our knowledge of human life
has attained the dignity of a genuine, independent science; during the
course of the century it has developed into one of the highest, most
interesting, and most important branches of knowledge. This "science
of the vital functions," physiology, had, it is true, been regarded
at a much earlier date as a desirable, if not a necessary, condition
of success in medical treatment, and had been constantly associated
with anatomy, the science of the structure of the body. But it was
only much later, and much more slowly, than the latter that it could
be thoroughly studied, as it had to contend with much more serious

The idea of life, as the opposite of death, naturally became the
subject of speculation at a very early age. In the living man, just
as in other living animals, there were certain peculiar changes,
especially movements, which were wanting in lifeless nature:
spontaneous locomotion, the beat of the heart, the drawing of the
breath, speech, and so forth. But the discrimination of such "organic
movements" from similar phenomena in inorganic bodies was by no means
easy, and was frequently impossible; the flowing stream, the flickering
flame, the rushing wind, the falling rock, seemed to man to exhibit
the same movements. It was quite natural that primitive man should
attribute an independent life to these "dead" bodies. He knew no more
of the real sources of movement in the one case than in the other.

We find the earliest scientific observations on the nature of man's
vital functions (as well as on his structure) in the Greek natural
philosophers and physicians of the sixth and fifth centuries before
Christ. The best collection of the physiological facts which were known
at that time is to be found in the _Natural History_ of Aristotle; a
great number of his assertions were probably taken from Democritus
and Hippocrates. The school of the latter had already made attempts
to explain the mystery; it postulated as the ultimate source of life
in man and the beasts a volatile "spirit of life" (Pneuma); and
Erasistratus (280 B.C.) already drew a distinction between the lower
and the higher "spirit of life," the _pneuma zoticon_ in the heart and
the _pneuma psychicon_ in the brain.

The credit of gathering these scattered truths into unity, and of
making the first attempt at a systematic physiology, belongs to the
great Greek physician Galen; we have already recognized in him the
first great anatomist of antiquity (cf. p. 23). In his researches
into the organs of the body he never lost sight of the question of
their vital activity, their functions; and even in this direction he
proceeded by the same comparative method, taking for his principal
study the animals which approach nearest to man. Whatever he learned
from these he applied directly to man. He recognized the value of
physiological experiment; in his vivisection of apes, dogs, and
swine he made a number of interesting experiments. Vivisection has
been made the object of a violent attack in recent years, not only
by the ignorant and narrow-minded, but by theological enemies of
knowledge and by perfervid sentimentalists; it is, however, one of the
_indispensable_ methods of research into the nature of life, and has
given us invaluable information on the most important questions. This
was recognized by Galen seventeen hundred years ago.

Galen reduces all the different functions of the body to three
groups, which correspond to the three forms of the _pneuma_, or vital
spirit. The _pneuma psychicon_--the soul--which resides in the brain
and nerves, is the cause of thought, sensation, and will (voluntary
movement); the _pneuma zoticon_--the heart--is responsible for the beat
of the heart, the pulse, and the temperature; the _pneuma physicon_,
seated in the liver, is the source of the so-called vegetative
functions, digestion and assimilation, growth and reproduction.
He especially emphasized the renewal of the blood in the lungs,
and expressed a hope that we should some day succeed in isolating
the permanent element in the atmosphere--the _pneuma_, as he calls
it--which is taken into the blood in respiration. More than fifteen
centuries elapsed before this _pneuma_--oxygen--was discovered by

In human physiology, as well as in anatomy, the great system of Galen
was for thirteen centuries the _Codex aureus_, the inviolable source of
all knowledge. The influence of Christianity, so fatal to scientific
culture, raised the same insuperable obstacles in this as in every
other branch of secular knowledge. Not a single scientist appeared
from the third to the sixteenth century who dared to make independent
research into man's vital activity, and transcend the limits of the
Galenic system. It was not until the sixteenth century that experiments
were made in that direction by a number of distinguished physicians
and anatomists (Paracelsus, Servetus, Vesalius, and others). In 1628
Harvey published his great discovery of the circulation of the blood,
and showed that the heart is a pump, which drives the red stream
unceasingly through the connected system of arteries and veins by a
rhythmic, unconscious contraction of its muscles. Not less important
were Harvey's researches into the procreation of animals, as a result
of which he formulated the well-known law: "Every living thing comes
from an egg" (_omne vivum ex ovo_).

The powerful impetus which Harvey gave to physiological observation and
experiment led to a great number of discoveries in the sixteenth and
seventeenth centuries. These were co-ordinated for the first time by
the learned Albrecht Haller about the middle of the last century; in
his great work, _Elementa Physiologiae_, he established the inherent
importance of the science, independently of its relation to practical
medicine. In postulating, however, a special "sensitive force or
sensibility" for neural action, and a special "irritability" for
muscular movement, Haller gave strong support to the erroneous idea of
a specific "vital force" (_vis vitalis_).

For more than a century afterwards, from the middle of the eighteenth
until the middle of the nineteenth century, medicine and (especially)
physiology were dominated by the old idea that a certain number of the
vital processes may be traced to physical and chemical causes, but that
others are the outcome of a special vital force which is independent
of physical agencies. However much scientists differed in their
conceptions of its nature and its relation to the "soul," they were all
agreed as to its independence of, and essential distinction from, the
chemico-physical forces of ordinary "matter"; it was a self-contained
force (_archaeus_), unknown in inorganic nature, which compelled
ordinary forces into its service. Not only the distinctly psychical
activity, the sensibility of the nerves and the irritability of the
muscles, but even the phenomena of sense activity, of reproduction,
and of development seemed so wonderful and so mysterious in their
sources that it was impossible to attribute them to simple physical
and chemical processes. As the free activity of the vital force
was purposive and conscious, it led, in philosophy, to a complete
_teleology_; especially did this seem indisputable when even the
"critical" philosopher Kant had acknowledged, in his famous critique
of the teleological position, that, though the mind's authority to
give a mechanical interpretation of all phenomena is theoretically
unlimited, yet its actual capacity for such interpretation does not
extend to the phenomena of organic life; here we are compelled to have
recourse to a _purposive_--therefore _supernatural_--principle. This
divergence of the _vital_ phenomena from the _mechanical_ processes of
life became, naturally, more conspicuous as science advanced in the
chemical and physical explanation of the latter. The circulation of the
blood and a number of other phenomena could be traced to mechanical
agencies; respiration and digestion were attributable to chemical
processes like those we find in inorganic nature. On the other hand,
it seemed impossible to do this with the wonderful performances of the
nerves and muscles, and with the characteristic life of the mind; the
co-ordination of all the different forces in the life of the individual
seemed also beyond such a mechanical interpretation. Hence there arose
a complete physiological dualism--an essential distinction was drawn
between inorganic and organic nature, between mechanical and vital
processes, between material force and life force, between the body and
the soul. At the beginning of the nineteenth century this vitalism was
firmly established in France by Louis Dumas, and in Germany by Reil.
Alexander Humboldt had already published a poetical presentation of it
in 1795, in his narrative of the _Legend of Rhodes_; it is repeated,
with critical notes, in his _Views of Nature_.

In the first half of the seventeenth century the famous philosopher
Descartes, starting from Harvey's discovery of the circulation of the
blood, put forward the idea that the body of man, like that of other
animals, is merely an intricate machine, and that its movements take
place under the same mechanical laws as the movements of an automaton
of human construction. It is true that Descartes, at the same time,
claimed for man the exclusive possession of a perfectly independent,
immaterial soul, and held that its subjective experience, thought,
was the only thing in the world of which we have direct and certain
cognizance ("_Cogito, ergo sum_"). Yet this dualism did not prevent
him from doing much to advance our knowledge of the mechanical life
processes in detail. Borelli followed (1660) with a reduction of the
movements of the animal body to purely physical laws, and Sylvius
endeavored, about the same time, to give a purely chemical explanation
of the phenomena of digestion and respiration; the former founded the
_iatromechanical_, the latter the _iatrochemical_, school of medicine.
However, these rational tendencies towards a natural, mechanical
explanation of the phenomena of life did not attain to a universal
acceptance and application; in the course of the eighteenth century
they fell entirely away before the advance of teleological vitalism.
The final disproof of the latter and a return to mechanism only became
possible with the happy growth of the new science of comparative
physiology in the forties of the present century.

Our knowledge of the vital functions, like our knowledge of the
structure of the human body, was originally obtained, for the most
part, not by direct observation of the human organism itself, but by
a study of the more closely related animals among the vertebrates,
especially the mammals. In this sense the very earliest beginning
of human anatomy and physiology was "comparative." But the distinct
science of "comparative physiology," which embraces the whole sphere
of life phenomena, from the lowest animal up to man, is a triumph of
the nineteenth century. Its famous creator was Johannes Müller, of
Berlin (born, the son of a shoemaker, at Coblentz, in 1801). For fully
twenty-five years--from 1833 to 1858--this most versatile and most
comprehensive biologist of our age evinced an activity at the Berlin
University, as professor and investigator, which is only comparable
with the associated work of Haller and Cuvier. Nearly every one of the
great biologists who have taught and worked in Germany for the last
sixty years was, directly or indirectly, a pupil of Johannes Müller.
Starting from the anatomy and physiology of man, he soon gathered all
the chief groups of the higher and lower animals within his sphere
of comparison. As, moreover, he compared the structure of extinct
animals with the living, and the healthy organism with the diseased,
endeavoring to bring together all the phenomena of life in a truly
philosophic fashion, he attained a biological knowledge far in advance
of his predecessors.

The most valuable fruit of these comprehensive studies of Johannes
Müller was his _Manual of Human Physiology_. This classical work
contains much more than the title indicates; it is the sketch of
a comprehensive "comparative biology." It is still unsurpassed in
respect of its contents and range of investigation. In particular,
we find the methods of observation and experiment applied in it as
masterfully as the philosophic processes of induction and deduction.
Müller was originally a vitalist, like all the physiologists of his
time. Nevertheless, the current idea of a vital force took a novel
form in his speculations, and gradually transformed itself into the
very opposite. For he attempted to explain the phenomena of life
mechanically in every department of physiology. His "transfigured"
vital force was not _above_ the physical and chemical laws of the rest
of nature but entirely bound up with them. It was, in a word, nothing
more than life itself--that is, the sum of all the movements which we
perceive in the living organism. He sought especially to give them
the same mechanical interpretation in the life of the senses and of
the mind as in the working of the muscles; the same in the phenomena
of circulation, respiration, and digestion as in generation and
development. Müller's success was chiefly due to the fact that he
always began with the simplest life phenomena of the lowest animals,
and followed them step by step in their gradual development up to the
very highest, to man. In this his method of _critical comparison_
proved its value both from the physiological and from the anatomical
point of view. Johannes Müller is, moreover, the only great scientist
who has equally cultivated these two branches of research, and combined
them with equal brilliancy. Immediately after his death his vast
scientific kingdom fell into four distinct provinces, which are now
nearly always represented by four or more chairs--human and comparative
anatomy, pathological anatomy, physiology, and the history of
evolution. This sudden division of Müller's immense realm of learning
in 1858 has been compared to the dissolution of the empire which
Alexander the Great had consolidated and ruled.

Among the many pupils of Johannes Müller who, either during his
lifetime or after his death, labored hard for the advancement of the
various branches of biology, one of the most fortunate--if not the
most important--was Theodor Schwann. When the able botanist Schleiden,
in 1838, indicated the cell as the common elementary organ of all
plants, and proved that all the different tissues of the plant are
merely combinations of cells, Johannes Müller recognized at once the
extraordinary possibilities of this important discovery. He himself
sought to point out the same composition in various tissues of the
animal body--for instance, in the spinal cord of vertebrates--and
thus led his pupil, Schwann, to extend the discovery to all the
animal tissues. This difficult task was accomplished by Schwann in
his _Microscopic Researches into the Accordance in the Structure and
Growth of Plants and Animals_ (1839). Thus was the foundation laid
of the "cellular theory," the profound importance of which, both in
physiology and anatomy, has become clearer and more widely recognized
in each subsequent year. Moreover, it was shown by two other pupils
of Johannes Müller that the activity of all organisms is, in the
ultimate analysis, the activity of the components of their tissues, the
microscopic cells--these were the able physiologist Ernst Brücke, of
Vienna, and the distinguished histologist Albert Kölliker, of Würzburg.
Brücke correctly denominated the cells the "elementary organisms," and
showed that, in the body of man and of all other animals, they are the
only actual, independent factors of the life process. Kölliker earned
special distinction, not only in the construction of the whole science
of histology, but particularly by showing that the animal ovum and its
products are simple cells.

Still, however widely the immense importance of the cellular theory for
all biological research was acknowledged, the "cellular physiology"
which is based on it only began an independent development very
recently. In this Max Verworn (of Jena) earned a twofold distinction.
In his _Psycho-physiological Studies of the Protistae_ (1889) he
showed, as a result of an ingenious series of experimental researches,
that the "theory of a cell-soul" which I put forward in 1866[11]
is completely established by an accurate study of the unicellular
protozoa, and that "the psychic phenomena of the protistæ form the
bridge which unites the chemical processes of inorganic nature with
the mental life of the highest animals." Verworn has further developed
these views, and based them on the modern theory of evolution, in
his _General Physiology_. This distinguished work returns to the
comprehensive point of view of Johannes Müller, in opposition to the
one-sided and narrow methods of those modern physiologists who think
to discover the nature of the vital phenomena by the exclusive aid of
chemical and physical experiments. Verworn showed that it is only by
Müller's comparative method and by a profound study of the physiology
of the cell that we can reach the higher stand-point which will give us
a comprehensive survey of the wonderful realm of the phenomena of life.
Only thus do we become convinced that the vital processes in man are
subject to the same physical and chemical laws as those of all other

The fundamental importance of the cellular theory for all branches of
biology was made clear in the second half of the nineteenth century,
not only by the rapid progress of morphology and physiology, but also
by the entire reform of that biological science which has always
been deemed most important on account of its relation to practical
medicine--pathology, or the science of disease. Many even of the
older physicians were convinced that human diseases were natural
phenomena, like all other manifestations of life, and should be studied
scientifically, like other vital functions. Particular schools of
medicine--the Iatrophysical and the Iatrochemical--had already, in
the seventeenth century, attempted to trace the sources of disease to
certain physical and chemical changes. However, the imperfect condition
of science at that period precluded any lasting results of these
efforts. Many of the older theories, which sought the nature of disease
in supernatural and mystical causes, were almost universally accepted
down to the middle of the nineteenth century.

It was then that Rudolf Virchow, another pupil of Müller, conceived
the happy idea of transferring the cellular theory from the healthy to
the diseased organism; he sought in the more minute metamorphoses of
the diseased cells and the tissues they composed the true source of
those larger changes which, in the form of disease, threaten the living
organism with peril and death. Especially during the seven years of
his professorship at Würzburg (1849-56) Virchow pursued his great task
with such brilliant results that his _Cellular Pathology_ (published in
1858) turned, at one stroke, the whole of pathology and the dependent
science of practical medicine into new and eminently fruitful paths.
This reform of medicine is significant for our present purpose in that
it led us to a monistic and purely scientific conception of disease. In
sickness, no less than in health, man is subject to the same eternal
"iron laws" of physics and chemistry as all the rest of the organic

Among the numerous classes of animals which modern zoology
distinguishes the mammals occupy a pre-eminent position, not only on
morphological grounds, but also for physiological reasons. As man
belongs to the class of mammals (see p. 27) by every portion of his
frame, we must expect him to share his characteristic functions with
the rest of the mammals. Such we find to be the case. The circulation
of the blood and respiration are accomplished in man under precisely
the same laws and in the same manner as in all the other mammals--_and
in these alone_; they are determined by the peculiar structure of
their heart and lungs. In mammals only is all the arterial blood
conducted from the left ventricle of the heart to the body by one,
the _left_, branch of the aorta, while in birds it passes along the
_right_ branch, and in reptiles along both branches. The blood of
mammals is distinguished from that of any other vertebrate by the
circumstance that its red cells have lost their nucleus (by reversion).
The respiratory movements are effected largely by the diaphragm in
this class of animals alone, because only in them does it form a
complete partition between the pectoral and abdominal cavities. Special
importance, however, in this highest class of animals, attaches to
the production of milk in the breasts (_mammae_), and to the peculiar
method of the rearing of the young, which entails the supplying of the
offspring with the mother's milk. As this nutritive process reacts most
powerfully on the other vital functions, and the maternal affection of
mammals must have arisen from this intimate form of rearing, the name
of the class justly reminds us of its great importance. In millions of
pictures, most of them produced by painters of the highest rank, the
"madonna with the child" is revered as the purest and noblest type of
maternal love--the instinct which is found in its extreme form in the
exaggerated tenderness of the mother-ape.

As the apes approach nearest to man of all the mammals in point of
structure, we shall expect to hear the same of their vital functions;
and that we find to be the case. Everybody knows how closely the
habits, the movements, the sense activity, the mental life, and the
parental customs of apes resemble those of man. Scientific physiology
proves the same significant resemblance in other less familiar
processes, particularly in the working of the heart, the division
of the breasts, and the sexual life. In the latter connection it is
especially noteworthy that the mature females of many kinds of apes
suffer a periodical discharge of blood from the womb, which corresponds
to the menstruation of the human female. The secretion of the milk in
the glands and the suctorial process also take place in the female ape
in precisely the same fashion as in women.

Finally, it is of especial interest that the speech of apes seems on
physiological comparison to be a stage in the formation of articulate
human speech. Among living apes there is an Indian species which is
musical; the _hylobates syndactylus_ sings a full octave in perfectly
pure, harmonious half-tones. No impartial philologist can hesitate any
longer to admit that our elaborate rational language has been slowly
and gradually developed out of the imperfect speech of our Pliocene
simian ancestors.



    The Older Embryology--The Theory of Preformation--The Theory of
    Scatulation: Haller and Leibnitz--The Theory of Epigenesis: C. F.
    Wolff--The Theory of Germinal Layers: Carl Ernst Baer--Discovery
    of the Human Ovum: Remak, Kölliker--The Egg-Cell and the
    Sperm-Cell--The Theory of the Gastræa--Protozoa and Metazoa--The
    Ova and the Spermatozoa: Oscar Hertwig--Conception--Embryonic
    Development in Man--Uniformity of the Vertebrate Embryo--The
    Germinal Membranes in Man--The Amnion, the Serolemma, and the
    Allantois--The Formation of the Placenta and the "After-Birth"--The
    _Decidua_ and the _Funiculus Umbilicalis_--The Discoid Placenta of
    Man and the Ape

Comparative ontogeny, or the science of the development of the
individual animal, is a child of the nineteenth century in even a truer
sense than comparative anatomy and physiology. How is the child formed
in the mother's womb? How do animals evolve from ova? How does the
plant come forth from the seed? These pregnant questions have occupied
the thoughtful mind for thousands of years. Yet it is only seventy
years since the embryologist Baer pointed out the correct means and
methods for penetrating into the mysteries of embryonic life; it is
only forty years since Darwin, by his reform of the theory of descent,
gave us the key which should open the long-closed door, and lead to
a knowledge of embryonic agencies. As I have endeavored to give a
complete, popular presentation of this very interesting but difficult
study in the first section of my _Anthropogeny_, I will confine myself
here to a brief survey and discussion of the most important phenomena.
Let us first cast a historical glance at the older ontogeny, and the
theory of preformation which is connected with it.

The classical works of Aristotle, the many-sided "father of science,"
are the oldest known scientific sources of embryology, as we found them
to be for comparative anatomy. Not only in his great natural history,
but also in a special small work, _Five Books on the Generation and
Development of Animals_, the great philosopher gives us a host of
interesting facts, adding many observations on their significance; it
was not until our own days that many of them were fully appreciated,
and, indeed, we may say, discovered afresh. Naturally, many fables and
errors are mixed up with them; it was all that was known at that time
of the hidden growth of the human germ. Yet during the long space of
the next two thousand years the slumbering science made no further
progress. It was not until the commencement of the seventeenth century
that there was a renewal of activity. In 1600 the Italian anatomist
Fabricius ab Aquapendente published at Padua the first pictures and
descriptions of the embryos of man and some of the higher animals; in
1687 the famous Marcello Malpighi, of Bologna, a distinguished pioneer
alike in zoology and botany, published the first consistent exposition
of the growth of the chick in the hatched egg.

All these older scientists were possessed with the idea that the
complete body, with all its parts, was already contained in the ovum
of animals, only it was so minute and transparent that it could not
be detected; that, therefore, the whole development was nothing more
than a _growth_, or an "unfolding," of the parts that were already
"infolded" (_involutae_). This erroneous notion, almost universally
accepted until the beginning of the present century, is called the
"preformation theory"; sometimes it is called the "evolution theory"
(in the literal sense of "unfolding"); but the latter title is accepted
by modern scientists for the very different theory of "transformation."

Closely connected with the preformation theory, and as a logical
consequence of it, there arose in the last century a further theory
which keenly interested all thoughtful biologists--the curious
"theory of scatulation." As it was thought that the outline of the
entire organism, with all its parts, was present in the egg, the
ovary of the embryo had to be supposed to contain the ova of the
following generation; these, again, the ova of the next, and so on
_in infinitum_! On that basis the distinguished physiologist Haller
calculated that God had created together, 6000 years ago--on the sixth
day of his creatorial labors--the germs of 200,000,000,000 men, and
ingeniously packed them all in the ovary of our venerable mother Eve.
Even the gifted philosopher Leibnitz fully accepted this conclusion,
and embodied it in his monadist theory; and as, on his theory, soul and
body are in eternal, inseparable companionship, the consequence had to
be accepted for the soul; "the souls of men have existed in organized
bodies in their ancestors from Adam downward--that is, from the very
beginning of things."

In the month of November, 1759, a young doctor of twenty-six years,
Caspar Friedrich Wolff (son of a Berlin tailor), published his
dissertation for the degree at Halle, under the title, _Theoria
Generationis_. Supported by a series of most laborious and painstaking
observations, he proved the entire falsity of the dominant theories of
preformation and scatulation. In the hatched egg there is at first no
trace of the coming chick and its organs; instead of it we find on top
of the yolk a small, circular, white disk. This thin "germinal disk"
becomes gradually round, and then breaks up into four folds, lying
upon each other, which are the rudiments of the four chief systems of
organs--the nervous system above, the muscular system underneath, the
vascular system (with the heart), and, finally, the alimentary canal.
Thus, as Wolff justly remarked, the embryonic development does not
consist in an unfolding of the preformed organs, but in a series of
new constructions; it is a true _epigenesis_. One part arises after
another, and all make their appearance in a simple form, which is very
different from the later structure. This only appears after a series of
most remarkable formations. Although this great discovery--one of the
most important of the eighteenth century--could be directly proved by a
verification of the facts Wolff had observed, and although the "theory
of generation" which was founded on it was in reality not a theory at
all, but a simple fact, it met with no sympathy whatever for half a
century. It was particularly retarded by the high authority of Haller,
who fought it strenuously with the dogmatic assertion that "there is
no such thing as development: no part of the animal body is formed
before another; all were created together." Wolff, who had to go to St.
Petersburg, was long in his grave before the forgotten facts he had
observed were discovered afresh by Oken at Jena, in 1806.

After Wolff's "epigenesis theory" had been established by Oken and
Neckel (whose important work on the development of the alimentary
canal was translated from Latin into German), a number of young German
scientists devoted themselves eagerly to more accurate embryological
research. The most important and successful of these was Carl Ernst
Baer. His principal work appeared in 1828, with the title, _History of
the Development of Animals: Observations and Reflections_. Not only
the phenomena of the formation of the germ are clearly illustrated
and fully described in it, but it adds a number of very pregnant
speculations. In particular, the form of the embryo of man and the
mammals is correctly presented, and the vastly different development
of the lower invertebrate animals is also considered. The two leaflike
layers which appear in the round germ disk of the higher vertebrates
first divide, according to Baer, into two further layers, and these
four germinal layers are transformed into four tubes, which represent
the fundamental organs--the skin layer, the muscular layer, the
vascular layer, and the mucous layer. Then, by very complicated
evolutionary processes, the later organs arise, in substantially the
same manner, in man and all the other vertebrates. The three chief
groups of invertebrates, which in their turn differ widely from each
other, have a very different development.

One of the most important of Baer's many discoveries was the finding of
the human ovum. Up to that time the little vesicles which are found in
great numbers in the human ovary and in that of all other mammals had
been taken for the ova. Baer was the first to prove, in 1827, that the
real ova are enclosed in these vesicles--the "Graafian follicles"--and
much smaller, being tiny spheres 1-120th inch in diameter, visible
to the naked eye as minute specks under favorable conditions. He
discovered likewise that from this tiny ovum of the mammal there
develops first a characteristic germ globule, a hollow sphere with
liquid contents, the wall of which forms the slender germinal membrane,
or blastoderm.

Ten years after Baer had given a firm foundation to embryological
science by his theory of germ layers a new task confronted it on the
establishment of the cellular theory in 1838. What is the relation of
the ovum and the layers which arise from it to the tissues and cells
which compose the fully developed organism? The correct answer to this
difficult question was given about the middle of this century by two
distinguished pupils of Johannes Müller--Robert Remak, of Berlin, and
Albert Kölliker, of Würzburg. They showed that the ovum is at first one
simple cell, and that the many germinal globules, or granules, which
arise from it by repeated segmentation, are also simple cells. From
this mulberry-like group of cells are constructed first the germinal
layers, and subsequently by differentiation, or division of labor,
all the different organs. Kölliker has the further merit of showing
that the seminal fluid of male animals is also a mass of microscopic
cells. The active pin-shaped "seed-animalcules," or _spermatozoa_, in
it are merely ciliated cells, as I first proved in the case of the
seed-filaments of the sponge in 1866. Thus it was proved that both
the materials of generation, the male sperm and the female ova, fell
in with the cellular theory. That was a discovery of which the great
philosophic significance was not appreciated until a much later date,
on a close study of the phenomena of conception in 1875.

All the older studies in embryonic development concern man and the
higher vertebrates, especially the embryonic bird, since hens' eggs
are the largest and most convenient objects for investigation, and
are plentiful enough to facilitate experiment; we can hatch them in
the incubator, as well as by the natural function of the hen, and
so observe from hour to hour, during the space of three weeks, the
whole series of formations, from the simple germ cell to the complete
organism. Even Baer had only been able to gather from such observations
the fact that the different classes of vertebrates agreed in the
characteristic form of the germ layers and the growth of particular
organs. In the innumerable classes of invertebrates, on the other
hand--that is, in the great majority of animals--the embryonic
development seemed to run quite a different course, and most of them
seemed to be altogether without true germinal layers. It was not until
about the middle of the century that such layers were found in some of
the invertebrates. Huxley, for instance, found them in the medusæ in
1849, and Kölliker in the cephalopods in 1844. Particularly important
was the discovery of Kowalewsky (1886) that the lowest vertebrate--the
lancelot, or amphioxus--is developed in just the same manner (and a
very original fashion it is) as an invertebrate, apparently quite
remote, tunicate, the sea-squirt, or ascidian. Even in some of the
worms, the radiata and the articulata, a similar formation of the
germinal layers was pointed out by the same observer. I myself was
then (since 1886) occupied with the embryology of the sponges, corals,
medusæ, and siphonophoræ, and, as I found the same formation of two
primary germ layers everywhere in these lowest classes of multicellular
animals, I came to the conclusion that this important embryonic
feature is common to the entire animal world. The circumstance that
in the sponges and the cnidaria (polyps, medusæ, etc.) the body
consists for a long time, sometimes throughout life, merely of two
simple layers of cells, seemed to me especially significant. Huxley
had already (1849) compared these, in the case of the medusæ, with the
two primary germinal layers of the vertebrates. On the ground of these
observations and comparisons I then, in 1872, in my _Philosophy of the
Calcispongiae_, published the "theory of the gastræa," of which the
following are the essential points:

I. The whole animal world falls into two essentially different groups,
the unicellular primitive animals (Protozoa) and the multicellular
animals with complex tissues (Metazoa). The entire organism of the
protozoon (the rhizopods of the infusoria) remains throughout life a
single simple cell (or occasionally a loose colony of cells without
the formation of tissue, a _coenobium_). The organism of the metazoon,
on the contrary, is only unicellular at the commencement, and is
subsequently built up of a number of cells which form tissues.

II. Hence the method of reproduction and development is very different
in each of these great categories of animals. The protozoa usually
multiply by _non-sexual_ means, by fission, gemmation, or spores;
they have no real ova and no sperm. The metazoa, on the contrary, are
divided into male and female sexes, and generally propagate sexually,
by means of true ova, which are fertilized by the male sperm.

III. Hence, further, true germinal layers, and the tissues which are
formed from them, are found only in the metazoa; they are entirely
wanting in the protozoa.

IV. In all the metazoa only two primary layers appear at first, and
these have always the same essential significance; from the _outer_
layer the external skin and the nervous system are developed; from the
_inner_ layer are formed the alimentary canal and all the other organs.

V. I called the germ, which always arises first from the impregnated
ovum, and which consists of these two primary layers, the "gut-larva,"
or the _gastrula_; its cup-shaped body with the two layers encloses
originally a simple digestive cavity, the primitive gut (the
_progaster_ or _archenteron_), and its simple opening is the primitive
mouth (the _prostoma_ or _blastoporus_). These are the earliest organs
of the multicellular body, and the two cell layers of its enclosing
wall, simple epithelia, are its earliest tissues; all the other organs
and tissues are a later and secondary growth from these.

VI. From this similarity, or _homology_, of the gastrula in all classes
of compound animals I drew the conclusion, in virtue of the biogenetic
law (p. 81), that all the metazoa come originally from one simple
ancestral form, the _gastraea_, and that this ancient (Laurentian),
long-extinct form had the structure and composition of the actual
gastrula, in which it is preserved by heredity.

VII. This phylogenetic conclusion, based on the comparison of
ontogenetic facts, is confirmed by the circumstance that there are
several of these gastræades still in existence (_gastraemaria_,
_cyemaria_, _physemaria_, etc.), and also some ancient forms of
other animal groups whose organization is very little higher (the
_olynthus_ of the sponges, the _hydra_, or common fresh-water polyp,
of the cnidaria, the _convoluta_ and other cryptocæla, or worms of the
simplest type, of the _platodes_).

VIII. In the further development of the various tissue-forming animals
from the gastrula we have to distinguish two principal groups. The
earlier and _lower_ types (the _coelenteria_ or _acoelomia_) have
no body cavity, no vent, and no blood; such is the case with the
gastræades, sponges, cnidaria, and platodes. The later and _higher_
types (the _caelomaria_ or _bilateria_), on the other hand, have a
true body cavity, and generally blood and a vent; to these we must
refer the worms and the higher types of animals which were evolved from
these later on, the echinodermata, mollusca, articulata, tunicata, and

Those are the main points of my "gastræa theory"; I have since
enlarged the first sketch of it (given in 1872), and have endeavored
to substantiate it in a series of "Studies on the gastræa theory"
(1873-84). Although it was almost universally rejected at first, and
fiercely combated for ten years by many authorities, it is now (and has
been for the last fifteen years) accepted by nearly all my colleagues.
Let us now see what far-reaching consequences follow from it, and
from the evolution of the germ, especially with regard to our great
question, "the place of man in nature."

The human ovum, like that of all other animals, is a single cell, and
this tiny globular egg cell (about the 120th of an inch in diameter)
has just the same characteristic appearance as that of all other
viviparous organisms. The little ball of protoplasm is surrounded
by a thick, transparent, finely reticulated membrane, called the
_zona pellucida_; even the little, globular, germinal vesicle (the
cell-nucleus), which is enclosed in the protoplasm (the cell-body),
is of the same size and the same qualities as in the rest of the
mammals. The same applies to the active spermatozoa of the male,
the minute, threadlike, ciliated cells of which millions are found
in every drop of the seminal fluid; on account of their lifelike
movements they were previously taken to be forms of life, as the name
indicates (spermatozoa--sperm animals). Moreover, the origin of both
these important sexual cells in their respective organs is the same in
man as in the other mammals; both the ova in the ovary of the female
and the spermatozoa in the spermarium of the male arise in the same
fashion--they always come from cells, which are originally derived from
the coelous epithelium, the layer of cells which clothes the cavity
of the body.

The most important moment in the life of every man, as in that of all
other complex animals, is the moment in which he begins his individual
existence; it is the moment when the sexual cells of both parents meet
and coalesce for the formation of a single simple cell. This new cell,
the impregnated egg cell, is the individual stem cell (the _cytula_),
the continued segmentation of which produces the cells of the germinal
layers and the gastrula. With the formation of this cytula, hence in
the process of conception itself, the existence of the personality, the
independent individual, commences. This ontogenic fact is supremely
important, for the most far-reaching conclusions may be drawn from
it. In the first place, we have a clear perception that man, like all
the other complex animals, inherits all his personal characteristics,
bodily and mental, from his parents; and, further, we come to the
momentous conclusion that the new personality which arises thus can lay
no claim to "immortality."

Hence the minute processes of conception and sexual generation are
of the first importance. We are, however, only familiar with their
details since 1875, when Oscar Hertwig, my pupil and fellow-traveller
at that time, began his researches into the impregnation of the egg
of the sea-urchin at Ajaccio, in Corsica. The beautiful capital of
the island in which Napoleon the Great was born, in 1769, was also
the spot in which the mysteries of animal conception were carefully
studied for the first time in their most important aspects. Hertwig
found that the one essential element in conception is the coalescence
of the two sexual cells and their nuclei. Only one out of the millions
of male ciliated cells which press round the ovum penetrates to its
nucleus. The nuclei of both cells, of the spermatozoon and of the ovum,
drawn together by a mysterious force, which we take to be a chemical
sense-activity, related to smell, approach each other and melt into
one. Thus, by the sensitive perception of the sexual nuclei, following
upon a kind of "erotic chemicotropism," a new cell is formed, which
unites in itself the inherited qualities of both parents; the nucleus
of the spermatozoon conveys the paternal features, the nucleus of the
ovum those of the mother, to the stem cell, from which the child is
to be developed. That applies both to the bodily and to the mental

The formation of the germinal layers by the repeated division of
the stem cell, the growth of the gastrula and of the later germ
structures which succeed it, take place in man in just the same manner
as in the other higher mammals, under the peculiar conditions which
differentiate this group from the lower vertebrates. In the earlier
stages of development these special characters of the placentalia are
not to be detected. The significant embryonic or larval form of the
chordula, which succeeds the gastrula, has substantially the same
structure in all vertebrates; a simple straight rod, the dorsal cord,
lies lengthways along the main axis of the shield-shaped body--the
"embryonic shield"; above the cord the spinal marrow develops out
of the outer germinal layer, while the gut makes its appearance
underneath. Then, on both sides, to the right and left of the axial
rod, appear the segments of the "pro-vertebræ" and the outlines of
the muscular plates, with which the formation of the members of the
vertebrate body begins. The gill-clefts appear on either side of the
fore-gut; they are the openings of the gullet, through which, in our
primitive fish-ancestors, the water which had entered at the mouth
for breathing purposes made its exit at the sides of the head. By a
tenacious heredity these gill-clefts, which have no meaning except for
our fish-like aquatic ancestors, are still preserved in the embryo of
man and all the other vertebrates. They disappear after a time. Even
after the five vesicles of the embryonic brain appear in the head,
and the rudiments of the eyes and ears at the sides, and after the
legs sprout out at the base of the fish-like embryo, in the form of
two roundish, flat buds, the foetus is still so like that of other
vertebrates that it is indistinguishable from them.

The substantial similarity in outer form and inner structure which
characterizes the embryo of man and other vertebrates in this early
stage of development is an embryological fact of the first importance;
from it, by the fundamental law of biogeny, we may draw the most
momentous conclusions. There is but one explanation of it--heredity
from a common parent form. When we see that, at a certain stage,
the embryos of man and the ape, the dog and the rabbit, the pig and
the sheep, although recognizable as higher vertebrates, cannot be
distinguished from each other, the fact can only be elucidated by
assuming a common parentage. And this explanation is strengthened when
we follow the subsequent divergence of these embryonic forms. The
nearer two animals are in their bodily structure, and, therefore, in
the scheme of nature, so much the longer do we find their embryos to
retain this resemblance, and so much the closer do they approach each
other in the ancestral tree of their respective group, so much the
closer is their genetic relationship. Hence it is that the embryos of
man and the anthropoid ape retain the resemblance much later, at an
advanced stage of development, when their distinction from the embryos
of other mammals can be seen at a glance. I have illustrated this
significant fact by a juxtaposition of corresponding stages in the
development of a number of different vertebrates in my _Natural History
of Creation_ and in my _Anthropogeny_.

The great phylogenetic significance of the resemblance we have
described is seen, not only in the comparison of the embryos of
vertebrates, but also in the comparison of their protective membranes.
All vertebrates of the three higher classes--reptiles, birds, and
mammals--are distinguished from the lower classes by the possession
of certain special foetal membranes, the amnion and the serolemma.
The embryo is enclosed in these membranes, or bags, which are full of
water, and is thus protected from pressure or shock. This provident
arrangement probably arose during the Permian period, when the oldest
reptiles, the _proreptilia_, the common ancestors of all the amniotes
(animals with an _amnion_), completely adapted themselves to a life on
land. Their direct ancestors, the amphibia, and the fishes are devoid
of these foetal membranes; they would have been superfluous to these
inhabitants of the water. With the inheritance of these protective
coverings are closely connected two other changes in the amniotes:
firstly, the entire disappearance of the gills (while the gill arches
and clefts continue to be inherited as "rudimentary organs"); secondly,
the construction of the _allantois_. This vesicular bag, filled with
water, grows out of the hind-gut in the embryo of all the amniotes,
and is nothing else than an enlargement of the bladder of their
amphibious ancestors. From its innermost and inferior section is formed
subsequently the permanent bladder of the amniotes, while the larger
outer part shrivels up. Usually this has an important part to play for
a long time as the respiratory organ of the embryo, a number of large
blood-vessels spreading out over its inner surface. The formation of
the membranes, the amnion and the serolemma, and of the allantois,
is just the same, and is effected by the same complicated process of
growth, in man as in all the other amniotes; _man is a true amniote_.

The nourishment of the foetus in the maternal womb is effected, as
is well known, by a peculiar organ, richly supplied with blood at its
surface, called the _placenta_. This important nutritive organ is a
spongy, round disk, from six to eight inches in diameter, about an
inch thick, and one or two pounds in weight; it is separated after
the birth of the child, and issues as the "after-birth." The placenta
consists of two very different parts, the foetal and the maternal
part. The latter contains highly developed sinuses, which retain the
blood conveyed to them by the arteries of the mother. On the other
hand, the foetal placenta is formed by innumerable branching tufts or
villi, which grow out of the outer surface of the allantois, and derive
their blood from the umbilical vessels. The hollow, blood-filled villi
of the foetal placenta protrude into the sinuses of the maternal
placenta, and the slender membrane between the two is so attenuated
that it offers no impediment to the direct interchange of material
through the nutritive blood-stream (by osmosis).

In the older and lower groups of the placentals the entire surface
of the chorion is covered with a number of short villi; these
"chorion-villi" take the form of pit-like depressions of the mucous
membrane of the mother, and are easily detached at birth. That
happens in most of the ungulata (the sow, camel, mare, etc.), the
cetacea, and the prosimiæ; these "mallo-placentalia" (with a _diffuse_
placenta) have been denominated the _indeciduata_. The same formation
is present in man and the other placentals in the beginning. It is
soon modified, however, as the villi on one part of the chorion are
withdrawn; while on the other part they grow proportionately stronger,
and unite intimately with the mucous membrane of the womb. It is in
consequence of this intimate blending that a portion of the uterus is
detached at birth, and carried away with loss of blood. This detachable
membrane--the _decidua_--is a characteristic of the higher placentalia,
which have, consequently, been grouped under the title of _deciduata_;
to that category belong the carnassia, rodentia, simiæ, and man. In
the carnassia and some of the ungulata (the elephant, for instance)
the placenta takes the form of a girdle, hence they are known as the
_zonoplacentalia_; in the rodentia, the insectivora (the mole and the
hedge-hog), the apes, and man, it takes the form of a disk.

Even ten years ago the majority of embryologists thought that man
was distinguished by certain peculiarities in the form of the
placenta--namely, by the possession of what is called the _decidua
reflexa_, and by a special formation of the umbilical chord which
unites the _decidua_ to the foetus. It was supposed that the rest
of the placentals, including the apes, were without these special
embryonic structures. The _funiculus umbilicalis_ is a smooth,
cylindrical cord, from sixteen to twenty-three inches long, and as
thick as the little finger. It forms the connecting link between the
foetus and the maternal placenta, since it conducts the nutritive
vessels from the body of the foetus to the placenta; it comprises,
besides, the pedicle of the allantois and the yelk-sac. The yelk-sac in
the human case forms the greater portion of the germinal vesicle during
the third week of gestation; but it shrivels up afterwards so that it
was formerly entirely missed in the mature foetus. Yet it remains all
the time in a rudimentary condition, and may be detected even after
birth as the little umbilical vesicle. Moreover, even the vesicular
structure of the allantois disappears at an early stage in the human
case; with a deflection of the amnion, it gives rise to the pedicle.
We cannot enter here into a discussion of the complicated anatomical
and embryological relations of these structures. I have described and
illustrated them in my _Anthropogeny_ (twenty-third chapter).

The opponents of evolution still appealed to these "special features"
of human embryology, which were supposed to distinguish man from all
the other mammals, even so late as ten years ago. But in 1890 Emil
Selenka proved that the same features are found in the anthropoid apes,
especially in the orang (_satyrus_), while the lower apes are without
them. Thus Huxley's pithecometra thesis was substantiated once more:
"The differences between man and the great apes are not so great as
are those between the manlike apes and the lower monkeys." The supposed
"evidences _against_ the near blood-relationship of man and the apes"
proved, on a closer examination of the real circumstances, to be strong
reasons in favor of it.

Every scientist who penetrates with open eyes into this dark but
profoundly interesting labyrinth of our embryonic development, and who
is competent to compare it critically with that of the rest of the
mammals, will find in it a most important aid towards the elucidation
of the descent of our species. For the various stages of our embryonic
development, in the character of _palingenetic_ phenomena of heredity,
cast a brilliant light on the corresponding stages of our ancestral
tree, in accordance with the great law of biogeny. But even the
_cenogenetic_ phenomena of adaptation, the formation of the temporary
foetal organs--the characteristic foetal membranes, and especially
the placenta--gives us sufficiently definite indications of our _close
genetic relationship with the primates_.



    Origin of Man--Mythical History of Creation--Moses and Linné--The
    Creation of Permanent Species--The Catastrophic Theory:
    Cuvier--Transformism: Goethe--Theory of Descent: Lamarck--Theory
    of Selection: Darwin--Evolution (Phylogeny)--Ancestral
    Trees--General Morphology--Natural History of Creation--Systematic
    Phylogeny--Fundamental Law of Biogeny--Anthropogeny--Descent of Man
    from the Ape--Pithecoid Theory--The Fossil Pithecanthropus of Dubois

The youngest of the great branches of the living tree of biology is
the science we call biological evolution, or _phylogeny_. It came into
existence much later, and under much more difficult circumstances, than
its natural sister, embryonic evolution or _ontogeny_. The object of
the latter was to attain a knowledge of the mysterious processes by
which the individual organism, plant or animal, developed from the egg.
Phylogeny has to answer the much more obscure and difficult question:
"What is the origin of the different organic species of plants and

Ontogeny (embryology and metamorphism) could follow the empirical
method of direct observation in the solution of its not remote problem;
it needed but to follow, day by day and hour by hour, the visible
changes which the foetus experiences during a brief period in the
course of its development from the ovum. Much more difficult was
the remote problem of phylogeny; for the slow processes of gradual
construction, which effect the rise of new species of animals and
plants, go on imperceptibly during thousands and even millions of
years. Their direct observation is possible only within very narrow
limits; the vast majority of these historical processes can only be
known by direct inference--by critical reflection, and by a comparative
use of empirical sciences which belong to very different fields of
thought, palæontology, ontogeny, and morphology. To this we must
add the immense opposition which was everywhere made to biological
evolution on account of the close connection between questions of
organic creation and supernatural myths and religious dogmas. For these
reasons it can easily be understood how it is that the scientific
existence of a true theory of origins was only secured, amid fierce
controversy, in the course of the last forty years.

Every serious attempt that was made before the beginning of the
nineteenth century to solve the problem of the origin of species
lost its way in the mythological labyrinth of the supernatural
stories of creation. The efforts of a few distinguished thinkers to
emancipate themselves from this tyranny and attain to a naturalistic
interpretation proved unavailing. A great variety of creation myths
arose in connection with their religion in all the ancient civilized
nations. During the Middle Ages triumphant Christendom naturally
arrogated to itself the sole right of pronouncing on the question; and,
the Bible being the basis of the structure of the Christian religion,
the whole story of creation was taken from the book of Genesis. Even
Carl Linné, the famous Swedish scientist, started from that basis
when, in 1735, in his classical _Systema Naturae_, he made the first
attempt at a systematic arrangement, nomenclature, and classification
of the innumerable objects in nature. As the best practical aid in that
attempt he introduced the well-known double or binary nomenclature; to
each kind of animals and plants he gave a particular specific name,
and added to it the wider-reaching name of the genus. A _genus_ served
to unite the nearest related _species_; thus, for instance, Linné
grouped under the genus "dog" (_canis_), as different species, the
house-dog (_canis familiaris_), the jackal (_canis aureus_), the wolf
(_canis lupus_) the fox (_canis vulpes_), etc. This binary nomenclature
immediately proved of such great practical assistance that it was
universally accepted, and is still always followed in zoological and
botanical classification.

But the theoretical dogma which Linné himself connected with his
practical idea of species was fraught with the gravest peril to
science. The first question which forced itself on the mind of the
thoughtful scientist was the question as to the nature of the concept
of species, its contents, and its range. And the creator of the idea
answered this fundamental question by a naïve appeal to the dominant
Mosaic legend of creation: "_Species tot sunt diversae, quot diversas
formas ab initio creavit infinitum ens_"--(There are just so many
distinct species as there were distinct types created in the beginning
by the Infinite). This theosophic dogma cut short all attempt at a
natural explanation of the origin of species. Linné was acquainted only
with the plant and animal worlds that exist to-day; he had no suspicion
of the much more numerous extinct species which had peopled the earth
with their varying forms in the earlier period of its development.

It was not until the beginning of the nineteenth century that we were
introduced to these fossil animals by Cuvier. In his famous work on
the fossil bones of the four-footed vertebrates he gave (1812) the
first correct description and true interpretation of many of these
fossil remains. He showed, too, that a series of very different animal
populations have succeeded each other in the various stages of the
earth's history. Since Cuvier held firmly to Linné's idea of the
absolute permanency of species, he thought their origin could only be
explained by the supposition that a series of great cataclysms and new
creations had marked the history of the globe; he imagined that all
living creatures were destroyed at the commencement of each of these
terrestrial revolutions, and an entirely new population was created
at its close. Although this "catastrophic theory" of Cuvier's led to
the most absurd consequences, and was nothing more than a bald faith
in miracles, it obtained almost universal recognition, and reigned
triumphant until the coming of Darwin.

It is easy to understand that these prevalent ideas of the absolute
unchangeability and supernatural creation of organic species could not
satisfy the more penetrating thinkers. We find several eminent minds
already, in the second half of the last century, busy with the attempt
to find a natural explanation of the "problem of creation." Pre-eminent
among them was the great German poet and philosopher, Wolfgang Goethe,
who, by his long and assiduous study of morphology, obtained, more than
a hundred years ago, a clear insight into the intimate connection of
all organic forms, and a firm conviction of a common natural origin.
In his famed _Metamorphosis of Plants_ (1790) he derived all the
different species of plants from one primitive type, and all their
different organs from one primitive organ--the leaf. In his vertebral
theory of the skull he endeavored to prove that the skulls of the
vertebrates--including man--were all alike made up of certain groups
of bones, arranged in a definite structure, and that these bones are
nothing else than transformed vertebræ. It was his penetrating study
of comparative osteology that led Goethe to a firm conviction of the
unity of the animal organization; he had recognized that the human
skeleton is framed on the same fundamental type as that of all other
vertebrates--"built on a primitive plan that only deviates more or less
to one side or other in its very constant features, and still develops
and refashions itself daily." This remodelling, or transformation,
is brought about, according to Goethe, by the constant interaction
of two powerful constructive forces--a centripetal force within the
organism, the "tendency to specification," and a centrifugal force
without, the tendency to variation, or the "idea of metamorphosis";
the former corresponds to what we now call heredity, the latter to
the modern idea of adaptation. How deeply Goethe had penetrated into
their character by these philosophic studies of the "construction and
reconstruction of organic natures," and how far, therefore, he must be
considered the most important precursor of Darwin and Lamarck,[12] may
be gathered from the interesting passages from his works which I have
collected in the fourth chapter of my _Natural History of Creation_.
These evolutionary ideas of Goethe, however, like analogous ideas of
Kant, Owen, Treviranus, and other philosophers of the commencement of
the century (which we have quoted in the above work), did not amount to
more than certain general conclusions. They had not that great lever
which the "natural history of creation" needed for its firm foundation
on a criticism of the dogma of fixed species; this lever was first
supplied by Lamarck.

The first thorough attempt at a scientific establishment of transformism
was made at the beginning of the nineteenth century by the great
French scientist Jean Lamarck, the chief opponent of his colleague,
Cuvier, at Paris. He had already, in 1802, in his _Observations on
Living Organisms_, expressed the new ideas as to the mutability and
formation of species, which he thoroughly established in 1809 in the
two volumes of his profound work, _Philosophie Zoologique_. In this
work he first gave expression to the correct idea, in opposition to
the prevalent dogma of fixed species, that the organic "species" is
an _artificial abstraction_, a concept of only relative value, like
the wider-ranging concepts of genus, family, order, and class. He
went on to affirm that all species are changeable, and have arisen
from older species in the course of very long periods of time. The
common parent forms from which they have descended were originally
very simple and lowly organisms. The first and oldest of them arose
by abiogenesis. While the type is preserved by _heredity_ in the
succession of generations, _adaptation_, on the other hand, effects
a constant modification of the species by change of habits and the
exercise of the various organs. Even our human organism has arisen in
the same natural manner, by gradual transformation, from a group of
pithecoid mammals. For all these phenomena--indeed, for all phenomena
both in nature and in the mind--Lamarck takes exclusively mechanical,
physical, and chemical activities to be the true efficient causes. His
magnificent _Philosophie Zoologique_ contains all the elements of a
purely monistic system of nature on the basis of evolution. I have
fully treated these achievements of Lamarck in the fourth chapter of my
_Anthropogeny_, and in the fourth chapter of the _Natural History of

Science had now to wait until this great effort to give a scientific
foundation to the theory of evolution should shatter the dominant myth
of a "specific creation, and open out the path of natural" development.
In this respect Lamarck was not more successful in resisting the
conservative authority of his great opponent, Cuvier, than was his
colleague and sympathizer, Geoffrey St. Hilaire, twenty years later.
The famous controversies which he had with Cuvier in the Parisian
Academy in 1830 ended with the complete triumph of the latter. I have
elsewhere fully described these conflicts, in which Goethe took so
lively an interest. The great expansion which the study of biology
experienced at that time, the abundance of interesting discoveries
in comparative anatomy and physiology, the establishment of the
cellular theory, and the progress of ontogeny, gave zoologists and
botanists so overwhelming a flood of welcome material to deal with
that the difficult and obscure question of the origin of species was
easily forgotten for a time. People rested content with the old dogma
of creation. Even when Charles Lyell refuted Cuvier's extraordinary
"catastrophic theory" in his _Principles of Geology_, in 1830, and
vindicated a natural, continuous evolution for the inorganic structure
of our planet, his simple principle of continuity found no one to
apply it to the inorganic world. The rudiments of a natural phylogeny
which were buried in Lamarck's works were as completely forgotten as
the germ of a natural ontogeny which Caspar Friedrich Wolff had given
fifty years earlier in his _Theory of Generation_. In both cases a full
half-century elapsed before the great idea of a natural development
won a fitting recognition. Only when Darwin (in 1859) approached the
solution of the problem from a different side altogether, and made
a happy use of the rich treasures of empirical knowledge which had
accumulated in the mean time, did men begin to think once more of
Lamarck as his great precursor.

The unparalleled success of Charles Darwin is well known. It shows him
to-day, at the close of the century, to have been, if not the greatest,
at least the most effective of its distinguished scientists. No other
of the many great thinkers of our time has achieved so magnificent, so
thorough, and so far-reaching a success with a single classical work as
Darwin did in 1859 with his famous _Origin of Species_. It is true that
the reform of comparative anatomy and physiology by Johannes Müller
had inaugurated a new and fertile epoch for the whole of biology, that
the establishment of the cellular theory by Schleiden and Schwann, the
reform of ontogeny by Baer, and the formulation of the law of substance
by Robert Mayer and Helmholtz were scientific facts of the first
importance; but no one of them has had so profound an influence on the
whole structure of human knowledge as Darwin's theory of the natural
origin of species. For it at once gave us the solution of the mystic
"problem of creation," the great "question of all questions"--the
problem of the true character and origin of man himself.

If we compare the two great founders of transformism, we find in
Lamarck a preponderant inclination to _deduction_, and to forming a
completely monistic scheme of nature; in Darwin we have a predominant
application of _induction_, and a prudent concern to establish the
different parts of the theory of selection as firmly as possible on a
basis of observation and experiment. While the French scientist far
outran the then limits of empirical knowledge, and rather sketched the
programme of future investigation, the English empiricist was mainly
preoccupied about securing a unifying principle of interpretation for
a mass of empirical knowledge which had hitherto accumulated without
being understood. We can thus understand how it was that the success
of Darwin was just as overwhelming as that of Lamarck was evanescent.
Darwin, however, had not only the signal merit of bringing all the
results of the various biological sciences to a common focus in the
principle of descent, and thus giving them a harmonious interpretation,
but he also discovered, in the principle of selection, that direct
cause of transformation which Lamarck had missed. In applying, as a
practical breeder, the experience of artificial selection to organisms
in a state of nature, and in recognizing in the "struggle for life" the
selective principle of natural selection, Darwin created his momentous
"theory of selection," which is what we properly call Darwinism.

One of the most pressing of the many important tasks which Darwin
proposed to modern biology was the reform of the zoological and
botanical system. Since the innumerable species of animals and plants
were not created by a supernatural miracle, but evolved by natural
processes, their ancestral tree is their "natural system." The first
attempt to frame a system in this sense was made by myself in 1866,
in my _General Morphology of Organisms_. The first volume of this
work ("General Anatomy") dealt with the "mechanical science of the
developed forms"; the second volume ("General Evolution") was occupied
with the science of the "developing forms." The systematic introduction
to the latter formed a "genealogical survey of the natural system
of organisms." Until that time the term "evolution" had been taken
to mean exclusively, both in zoology and botany, the development of
individual organisms--embryology, or metamorphic science. I established
the opposite view, that this history of the embryo (ontogeny) must be
completed by a second, equally valuable, and closely connected branch
of thought--the history of the race (phylogeny). Both these branches
of evolutionary science are, in my opinion, in the closest causal
connection; this arises from the reciprocal action of the laws of
heredity and adaptation; it has a precise and comprehensive expression
in my "fundamental law of biogeny."

As the new views I had put forward in my _General Morphology_ met with
very little notice, and still less acceptance, from my scientific
colleagues, in spite of their severely scientific setting, I thought
I would make the most important of them accessible to a wider circle
of informed readers by a smaller work, written in a more popular
style. This was done in 1868, in _The Natural History of Creation_ (a
series of popular scientific lectures on evolution in general, and the
systems of Darwin, Goethe, and Lamarck in particular). If the success
of my _General Morphology_ was far below my reasonable anticipation,
that of _The Natural History of Creation_ went far beyond it. In a
period of thirty years nine editions and twelve different translations
of it have appeared. In spite of its great defects, the book has
contributed much to the popularization of the main ideas of modern
evolution. Still, I could only give the barest outlines in it of my
chief object, the phylogenetic construction of a natural system. I
have, therefore, given the complete proof, which is wanting in the
earlier work, of the phylogenetic system in a subsequent larger work,
my _Systematic Phylogeny_ (outlines of a natural system of organisms
on the basis of their specific development). The first volume of
it deals with the protists and plants (1894), the second with the
invertebrate animals (1896), the third with the vertebrates (1895). The
ancestral tree of both the smaller and the larger groups is carried
on in this work as far as my knowledge of the three great "ancestral
documents"--palæontology, ontogeny, and morphology--qualified me to
extend it.

I had already, in my _General Morphology_ (at the end of the fifth
book), described the close causative connection which exists, in
my opinion, between the two branches of organic evolution as one
of the most important ideas of transformism, and I had framed a
precise formula for it in a number of "theses on the causal nexus of
biontic and phyletic development": "_Ontogenesis is a brief and rapid
recapitulation of phylogenesis_, determined by the physiological
functions of heredity (generation) and adaptation (maintenance)."
Darwin himself had emphasized the great significance of his theory
for the elucidation of embryology in 1859, and Fritz Müller had
endeavored to prove it as regards the Crustacea in the able little
work, _Facts and Arguments for Darwin_ (1864). My own task has been
to prove the universal application and the fundamental importance of
the biogenetic law in a series of works, especially in the _Biology
of the Calcispongiae_ (1872), and in _Studies on the Gastraea Theory_
(1873-1884). The theory of the homology of the germinal layers and of
the relations of _palingenesis_ to _cenogenesis_ which I have exposed
in them has been confirmed subsequently by a number of works of other
zoologists. That theory makes it possible to follow nature's law of
unity in the innumerable variations of animal embryology; it gives us
for their ancestral history a common derivation from a simple primitive
stem form.

The far-seeing founder of the theory of descent, Lamarck, clearly
recognized in 1809 that it was of universal application; that even man
himself, the most highly developed of the mammals, is derived from the
same stem as all the other mammals; and that this in its turn belongs
to the same older branch of the ancestral tree as the rest of the
vertebrates. He had even indicated the agencies by which it might be
possible to explain man's descent from the apes as the nearest related
mammals. Darwin, who was, naturally, of the same conviction, purposely
avoided this least acceptable consequence of his theory in his chief
work in 1859, and put it forward for the first time in his _Descent of
Man_ in 1871. In the mean time (1863) Huxley had very ably discussed
this most important consequence of evolution in his famous _Place of
Man in Nature_. With the aid of comparative anatomy and ontogeny,
and the support of the facts of palæontology, Huxley proved that the
"descent of man from the ape" is a necessary consequence of Darwinism,
and that no other scientific explanation of the origin of the human
race is possible. Of the same opinion was Karl Gegenbaur, the most
distinguished representative of comparative anatomy, who lifted his
science to a higher level by a consistent and ingenious application of
the theory of descent.

As a further consequence of the "pithecoid theory" (the theory of the
descent of man from the ape) there now arose the difficult task of
investigating, not only the nearest related mammal ancestors of man
in the Tertiary epoch, but also the long series of the older animal
ancestors which had lived in earlier periods of the earth's history and
been developed in the course of countless millions of years. I had made
a start with the hypothetical solution of this great historic problem
in my _General Morphology_; a further development of it appeared in
1874 in my _Anthropogeny_ (first section, Origin of the Individual;
second section, Origin of the Race). The fourth, enlarged, edition of
this work (1891) contains that theory of the development of man which
approaches nearest, in my own opinion, to the still remote truth, in
the light of our present knowledge of the documentary evidence. I was
especially preoccupied in its composition to use the three empirical
"documents"--palæontology, ontogeny, and morphology (or comparative
anatomy)--as evenly and harmoniously as possible. It is true that my
hypotheses were in many cases supplemented and corrected in detail by
later phylogenetic research; yet I am convinced that the ancestral tree
of human origin which I have sketched therein is substantially correct.
For the historical succession of vertebrate fossils corresponds
completely with the morphological evolutionary scale which is revealed
to us by comparative anatomy and ontogeny. After the Silurian fishes
come the _dipnoi_ of the Devonian period--the Carboniferous amphibia,
the Permian reptilia, and the Mesozoic mammals. Of these, again, the
lowest forms, the monotremes, appear first in the Triassic period,
the marsupials in the Jurassic, and then the oldest placentals in
the Cretaceous. Of the placentals, in turn, the first to appear in
the oldest Tertiary period (the Eocene) are the lowest primates,
the prosimiæ, which are followed by the simiæ in the Miocene. Of the
catarrhinæ, the cynopitheci precede the anthropomorpha; from one branch
of the latter, during the Pliocene period, arises the ape-man without
speech (the _pithecanthropus alalus_); and from him descends, finally,
speaking man.

The chain of our earlier invertebrate ancestors is much more difficult
to investigate and much less safe than this tree of our vertebrate
predecessors; we have no fossilized relics of their soft, boneless
structures, so palæontology can give us no assistance in this case.
The evidence of comparative anatomy and ontogeny, therefore, becomes
all the more important. Since the human embryo passes through the
same _chordula_-stage as the germs of all other vertebrates, since
it evolves, similarly, out of two germinal layers of a _gastrula_,
we infer, in virtue of the biogenetic law, the early existence of
corresponding ancestral forms--vermalia, gastræada, etc. Most important
of all is the fact that the human embryo, like that of all other
animals, arises originally from a single cell; for this "stem-cell"
(_cytula_)--the impregnated egg cell--points indubitably to a
corresponding unicellular ancestor, a primitive, Laurentian protozoon.

For the purpose of our monistic philosophy, however, it is a matter of
comparative indifference how the succession of our animal predecessors
may be confirmed in detail. Sufficient for us, as an incontestable
historical fact, is the important thesis that man descends immediately
from the ape, and secondarily from a long series of lower vertebrates.
I have laid stress on the logical proof of this "pithecometra-thesis"
in the seventh book of the _General Morphology_: "The thesis that
man has been evolved from lower vertebrates, and immediately from the
_simiae_, is a special inference which results with absolute necessity
from the general inductive law of the theory of descent."

For the definitive proof and establishment of this fundamental
pithecometra-thesis the palæontological discoveries of the last
thirty years are of the greatest importance; in particular, the
astonishing discoveries of a number of extinct mammals of the Tertiary
period have enabled us to draw up clearly in its main outlines the
evolutionary history of this most important class of animals, from
the lowest oviparous monotremes up to man. The four chief groups
of the placentals, the heterogeneous legions of the carnassia, the
rodentia, the ungulata, and the primates, seem to be separated by
profound gulfs, when we confine our attention to their representatives
of to-day. But these gulfs are completely bridged, and the sharp
distinctions of the four legions are entirely lost, when we compare
their extinct predecessors of the Tertiary period, and when we go
back into the Eocene twilight of history, in the oldest part of the
Tertiary period--at least three million years ago. There we find the
great sub-class of the placentals, which to-day comprises more than
two thousand five hundred species, represented by only a small number
of little, insignificant "proplacentals"; and in these _prochoriata_
the characters of the four divergent legions are so intermingled and
toned down that we cannot in reason do other than consider them as the
precursors of those features. The oldest carnassia (the _ictopsales_),
the oldest rodentia (the _esthonychales_), the oldest ungulata (the
_condylarthrales_) and the oldest primates (the _lemuravales_), all
have the same fundamental skeletal structure, and the same typical
dentition of the primitive placentals, consisting of forty-four teeth
(three incisors, one canine, four premolars, and three molars in each
half of the jaw); all are characterized by the small size and the
imperfect structure of the brain (especially of its chief part, the
cortex, which does not become a true "organ of thought" until later on
in the Miocene and Pliocene representatives); they have all short legs
and five-toed, flat-soled feet (_plantigrada_). In many cases among
these oldest placentals of the Eocene period it was very difficult
to say at first whether they should be classed with the carnassia,
rodentia, ungulata, or primates; so very closely, even to confusion,
do these four groups of the placentals, which diverge so widely
afterwards, approach each other at that time. Their common origin from
a single ancestral group follows incontestably. These _prochoriata_
lived in the preceding Cretaceous period (more than three million years
ago), and were probably developed in the Jurassic period from a group
of insectivorous marsupials (_amphitheria_) by the formation of a
primitive _placenta diffusa_, a placenta of the simplest type.

But the most important of all the recent palaeontological discoveries
which have served to elucidate the origin of the placentals relate
to our own stem, the legion of primates. Formerly fossil remains of
the primates were very scarce. Even Cuvier, the great founder of
palaeontology, maintained until his last day (1832) that there were no
fossilized primates; he had himself, it is true, described the skull
of an Eocene prosimiæ (_adapis_), but he had wrongly classed it with
the ungulata. However, during the last twenty years a fair number of
well-preserved fossilized skeletons of prosimiæ and simiæ have been
discovered; in them we find all the chief intermediate members which
complete the connecting chain of ancestors from the oldest prosimiæ to

The most famous and most interesting of these discoveries is the
fossil ape-man of Java, the much-talked-of _pithecanthropus erectus_,
found by a Dutch military doctor, Eugen Dubois, in 1894. It is in
truth the much-sought "missing link," supposed to be wanting in
the chain of primates, which stretches unbroken from the lowest
catarrhinæ to the highest-developed man. I have dealt exhaustively
with the significance of this discovery in the paper which I read on
August 26, 1898, at the Fourth International Zoological Congress at
Cambridge.[13] The palæontologist, who knows the conditions of the
formation and preservation of fossils, will think the discovery of the
pithecanthropus an unusually lucky accident. The apes, being arboreal,
seldom came into the circumstances (unless they happened to fall into
the water) which would secure the preservation and petrifaction of
their skeleton. Thus, by the discovery of this fossil man-monkey of
Java the descent of man from the ape has become just as clear and
certain from the palæontological side as it was previously from the
evidence of comparative anatomy and ontogeny. We now have all the
principal documents which tell the history of our race.



    Fundamental Importance of Psychology--Its Definition and
    Methods--Divergence of Views Thereon--Dualistic and Monistic
    Psychology--Relation to the Law of Substance--Confusion
    of Ideas--Psychological Metamorphoses: Kant, Virchow,
    Du Bois-Reymond--Methods of Research of Psychic
    Science--Introspective Method (Self-Observation)--Exact
    Method (Psycho-Physics)--Comparative Method (Animal
    Psychology)--Psychological Change of Principles:
    Wundt--Folk-Psychology and Ethnography: Bastian--Ontogenetic
    Psychology: Preyer--Phylogenetic Psychology: Darwin, Romanes

The phenomena which are comprised under the title of the "life of
the soul," or the psychic activity, are, on the one hand, the most
important and interesting, on the other the most intricate and
problematical, of all the phenomena we are acquainted with. As the
knowledge of nature, the object of the present philosophic study,
is itself a part of the life of the soul, and as anthropology, and
even cosmology, presuppose a correct knowledge of the "psyche," we
may regard psychology, the scientific study of the soul, both as the
foundation and the postulate of all other sciences. From another
point of view it is itself a part of philosophy, or physiology, or

The great difficulty of establishing it on a naturalistic basis
arises from the fact that psychology, in turn, presupposes a correct
acquaintance with the human organism, especially the brain, the chief
organ of psychic activity. The great majority of "psychologists" have
little or no acquaintance with these anatomical foundations of the
soul, and thus it happens that in no other science do we find such
contradictions and untenable notions as to its proper meaning and
its essential object as are current in psychology. This confusion
has become more and more palpable during the last thirty years, in
proportion as the immense progress of anatomy and physiology has
increased our knowledge of the structure and the functions of the chief
psychic organ.

What we call the soul is, in my opinion, a natural phenomenon; I
therefore consider psychology to be a branch of natural science--a
section of physiology. Consequently, I must emphatically assert
from the commencement that we have no different methods of research
for that science than for any of the others; we have in the first
place observation and experiment, in the second place the theory of
evolution, and in the third place metaphysical speculation, which
seek to penetrate as far as possible into the cryptic nature of the
phenomena by inductive and deductive reasoning. However, with a view
to a thorough appreciation of the question, we must first of all put
clearly before the reader the antithesis of the dualistic and the
monistic theories.

The prevailing conception of the psychic activity, which we contest,
considers soul and body to be two distinct entities. These two
entities can exist independently of each other; there is no intrinsic
necessity for their union. The organized body is a mortal, material
nature, chemically composed of living protoplasm and its compounds
(plasma-products). The soul, on the other hand, is an immortal,
immaterial being, a spiritual agent, whose mysterious activity
is entirely incomprehensible to us. This trivial conception is,
as such, spiritualistic, and its contradictory is, in a certain
sense, materialistic. It is, at the same time, supernatural and
transcendental, since it affirms the existence of forces which can
exist and operate without a material basis; it rests on the assumption
that outside of and beyond nature there is a "spiritual," immaterial
world, of which we have no experience, and of which we can learn
nothing by natural means.

This hypothetical "spirit world," which is supposed to be entirely
independent of the material universe, and on the assumption of which
the whole artificial structure of the dualistic system is based, is
purely a product of poetic imagination; the same must be said of the
parallel belief in the "immortality of the soul," the scientific
impossibility of which we must prove more fully later on (chap. xi.).
If the beliefs which prevail in these credulous circles had a sound
foundation, the phenomena they relate to could not be subject to the
"law of substance"; moreover, this single exception to the highest
law of the cosmos must have appeared very late in the history of the
organic world, since it only concerns the "soul" of man and of the
higher animals. The dogma of "free will," another essential element
of the dualistic psychology, is similarly irreconcilable with the
universal law of substance.

Our own naturalistic conception of the psychic activity sees in it a
group of vital phenomena, which are dependent on a definite material
substratum, like all other phenomena. We shall give to this material
basis of all psychic activity, without which it is inconceivable,
the provisional name of "psychoplasm"; and for this good reason--that
chemical analysis proves it to be a body of the group we call
protoplasmic bodies the albuminoid carbon-combinations which are at
the root of all vital processes. In the higher animals, which have a
nervous system and sense-organs, "neuroplasm," the nerve-material,
has been differentiated out of psychoplasm. Our conception is, in
this sense, materialistic. It is at the same time empirical and
naturalistic, for our scientific experience has never yet taught us the
existence of forces that can dispense with a material substratum, or of
a spiritual world over and above the realm of nature.

Like all other natural phenomena, the psychic processes are subject to
the supreme, all-ruling law of substance; not even in this province
is there a single exception to this highest cosmological law (compare
chap. xii.). The phenomena of the lowly psychic life of the unicellular
protist and the plant, and of the lowest animal forms--their
irritability, their reflex movements, their sensitiveness and instinct
of self-preservation--are directly determined by physiological action
in the protoplasm of their cells--that is, by physical and chemical
changes which are partly due to heredity and partly to adaptation.
And we must say just the same of the higher psychic activity of the
higher animals and man, of the formation of ideas and concepts, of
the marvellous phenomena of reason and consciousness; for the latter
have been phylogenetically evolved from the former, and it is merely
a higher degree of integration or centralization, of association
or combination of functions which were formerly isolated, that has
elevated them in this manner.

The first task of every science is the clear definition of the object
it has to investigate. In no science, however, is this preliminary
task so difficult as in psychology; and this circumstance is the
more remarkable since logic, the science of defining, is itself a
part of psychology. When we compare all that has been said by the
most distinguished philosophers and scientists of all ages on the
fundamental idea of psychology, we find ourselves in a perfect chaos
of contradictory notions. What, really, is the "soul"? What is its
relation to the "mind"? What is the inner meaning of "consciousness"?
What is the difference between "sensation" and "sentiment"? What is
"instinct"? What is the meaning of "free will"? What is "presentation"?
What is the difference between "intellect" and "reason"? What is the
true nature of "emotion"? What is the relation between all these
"psychic phenomena" and the "body"? The answers to these and many other
cognate questions are infinitely varied; not only are the views of the
most eminent thinkers on these questions widely divergent, but even the
same scientific authority has often completely changed his views in the
course of his psychological development. Indeed, this "psychological
metamorphosis" of so many thinkers has contributed not a little to the
_colossal confusion of ideas_ which prevails in psychology more than in
any other branch of knowledge.

The most interesting example of such an entire change of objective
and subjective psychological opinions is found in the case of the
most influential leader of German philosophy, Immanuel Kant. The
young, severely _critical_ Kant came to the conclusion that the three
great buttresses of mysticism--"God, freedom, and immortality"--were
untenable in the light of "pure reason"; the older, _dogmatic_ Kant
found that these three great hallucinations were postulates of
"practical reason," and were, as such, indispensable. The more the
distinguished modern school of "Neokantians" urges a "return to Kant"
as the only possible salvation from the frightful jumble of modern
metaphysics, the more clearly do we perceive the undeniable and fatal
contradiction between the fundamental opinions of the young and the
older Kant. We shall return to this point later on.

Other interesting examples of this change of views are found in two of
the most famous living scientists, R. Virchow and E. du Bois-Reymond;
the metamorphoses of their fundamental views on psychology cannot
be overlooked, as both these Berlin biologists have played a most
important part at Germany's greatest university for more than forty
years, and have, therefore, directly and indirectly, had a most
profound influence on the modern mind. Rudolph Virchow, the eminent
founder of cellular pathology, was a _pure monist_ in the best days of
his scientific activity, about the middle of the century; he passed at
that time as one of the most distinguished representatives of the newly
awakened _materialism_, which appeared in 1855, especially through two
famous works, almost contemporaneous in appearance--Ludwig Büchner's
_Matter and Force_ and Carl Vogt's _Superstition and Science_. Virchow
published his general biological views on the vital processes in
man--which he takes to be purely mechanical natural phenomena--in a
series of distinguished papers in the first volumes of the _Archiv
für pathologische Anatomie_, which he founded. The most important of
these articles, and the one in which he most clearly expresses his
monistic views of that period, is that on "The Tendencies Towards
Unity in Scientific Medicine" (1849). It was certainly not without
careful thought, and a conviction of its philosophic value, that
Virchow put this "medical confession of faith" at the head of his
_Collected Essays on Scientific Medicine_ in 1856. He defended in it,
clearly and definitely, the fundamental principles of monism, which I
am presenting here with a view to the solution of the world-problem;
he vindicated the exclusive title of empirical science, of which the
only reliable sources are sense and brain activity; he vigorously
attacked anthropological dualism, the alleged "revelation," and
the transcendental philosophy, with their two methods--"faith and
anthropomorphism." Above all, he emphasized the monistic character of
anthropology, the inseparable connection of spirit and body, of force
and matter. "I am convinced," he exclaims, at the end of his preface,
"that I shall never find myself compelled to deny the thesis of _the
unity_ of human nature." Unhappily, this "conviction" proved to be a
grave error. Twenty-eight years afterwards Virchow represented the
diametrically opposite view; it is to be found in the famous speech on
"The Liberty of Science in Modern States," which he delivered at the
Scientific Congress at Munich in 1877, and which contains attacks that
I have repelled in my _Free Science and Free Teaching_ (1878).

In Emil du Bois-Reymond we find similar contradictions with regard
to the most important and fundamental theses of philosophy. The
more completely the distinguished orator of the Berlin Academy had
defended the main principles of the monistic philosophy, the more he
had contributed to the refutation of vitalism and the transcendental
view of life, so much the louder was the triumphant cry of our
opponents when in 1872, in his famous _Ignorabimus-Speech_, he spoke
of consciousness as an insoluble problem, and opposed it to the other
functions of the brain as a supernatural phenomenon. I return to the
point in the tenth chapter.

The peculiar character of many of the psychic phenomena, especially
of consciousness, necessitates certain modifications of our ordinary
scientific methods. We have, for instance, to associate with the
customary _objective_, external observation, the _introspective_
method, the _subjective_, internal observation which scrutinizes
our own personality in the mirror of consciousness. The majority of
psychologists have started from this "certainty of the ego": "_Cogito
ergo sum_," as Descartes said--I think, therefore I am. Let us first
cast a glance at this way of inquiry, and then deal with the second,
complementary, method.

By far the greater part of the theories of the soul which have been
put forward during the last two thousand years or more are based on
introspective inquiry--that is, on "self-observation," and on the
conclusions which we draw from the association and criticism of these
subjective experiences. Introspection is the only possible method of
inquiry for an important section of psychology, especially for the
study of consciousness. Hence this cerebral function occupies a special
position, and has been a more prolific source of philosophic error than
any of the others (cf. chap. x.). It is, however, most unsatisfactory,
and it leads to entirely false or incomplete notions, to take this
self-observation of the mind to be the chief, or, especially, to be
the only source of mental science, as has happened in the case of
many and distinguished philosophers. A great number of the principal
psychic phenomena, particularly the activity of the senses and speech,
can only be studied in the same way as every other vital function of
the organism--that is, firstly, by a thorough anatomical study of
their organs, and, secondly, by an exact physiological analysis of
the functions which depend on them. In order, however, to complete
this external study of the mental life, and to supplement the results
of _internal_ observation, one needs a thorough knowledge of human
anatomy, histology, ontogeny, and physiology. Most of our so-called
"psychologists" have little or no knowledge of these indispensable
foundations of anthropology; they are, therefore, incompetent to
pronounce on the character even of their own "soul." It must be
remembered, too, that the distinguished personality of one of these
psychologists usually offers a specimen of an educated mind of the
highest civilized races; it is the last link of a long ancestral chain,
and the innumerable older and inferior links are indispensable for
its proper understanding. Hence it is that most of the psychological
literature of the day is so much waste paper. The introspective method
is certainly extremely valuable and indispensable; still it needs the
constant co-operation and assistance of the other methods.

In proportion as the various branches of the human tree of knowledge
have developed during the century, and the methods of the different
sciences have been perfected, the desire has grown to make them
_exact_; that is, to make the study of phenomena as purely empirical
as possible, and to formulate the laws that result as clearly as
the circumstances permit--if possible, _mathematically_. The latter
is, however, only feasible in a small province of human knowledge,
especially in those sciences in which there is question of measurable
quantities; in mathematics, in the first place, and to a greater or
less extent in astronomy, mechanics, and a great part of physics and
chemistry. Hence these studies are called "exact sciences" in the
narrower sense. It is, however, productive only of error to call all
the physical sciences _exact_, and oppose them to the historical,
mental, and moral sciences. The greater part of physical science can
no more be treated as an _exact_ science than history can; this is
especially true of biology and of its subsidiary branch, psychology.
As psychology is a part of physiology, it must, as a general rule,
follow the chief methods of that science. It must establish the facts
of psychic activity by empirical methods as much as possible, by
observation and experiment, and it must then gather the laws of the
mind by inductive and deductive inferences from its observations,
and formulate them with the utmost distinctness. But, for obvious
reasons, it is rarely possible to formulate them mathematically. Such
a procedure is only profitable in one section of the physiology of
the senses; it is not practicable in the greater part of cerebral

One small section of physiology, which seems amenable to the "exact"
method of investigation, has been carefully studied for the last
twenty years and raised to the position of a separate science under
the title of _psycho-physics_. Its founders, the physiologists Theodor
Fechner and Ernst Heinrich Weber, first of all closely investigated
the dependence of sensations on the external stimuli that act on the
organs of sense, and particularly the quantitative relation between
the strength of the stimulus and the intensity of the sensation. They
found that a certain minimum strength of stimulus is requisite for
the excitement of a sensation, and that a given stimulus must be
varied to a definite amount before there is any perceptible change
in the sensation. For the highest sensations (of sight, hearing, and
pressure) the law holds good that their variations are proportionate
to the changes in the strength of the stimulus. From this empirical
"law of Weber" Fechner inferred, by mathematical operations, his
"fundamental law of psycho-physics," according to which the intensity
of a sensation increases in arithmetical progression, the strength
of the stimulus in geometrical progression. However, Fechner's law
and other psycho-physical laws are frequently contested, and their
"exactness" is called into question. In any case modern psycho-physics
has fallen far short of the great hopes with which it was greeted
twenty years ago; the field of its applicability is extremely limited.
One important result of its work is that it has proved the application
of physical laws in one, if only a small, branch of the life of the
"soul"--an application which was long ago postulated on principle by
the materialist psychology for the whole province of mental life. In
this, as in many other branches of physiology, the "exact" method has
proved inadequate and of little service. It is the ideal to aim at
everywhere, but it is unattainable in most cases. Much more profitable
are the comparative and genetic methods.

The striking resemblance of man's psychic activity to that of
the higher animals--especially our nearest relatives among the
mammals--is a familiar fact. Most uncivilized races still make no
material distinction between the two sets of mental processes, as
the well-known animal fables, the old legends, and the idea of the
transmigration of souls prove. Even most of the philosophers of
classical antiquity shared the same conviction, and discovered no
essential qualitative difference, but merely a quantitative one,
between the soul of man and that of the brute. Plato himself, who was
the first to draw a fundamental distinction between soul and body,
made one and the same soul (or "idea") pass through a number of animal
and human bodies in his theory of metempsychosis. It was Christianity,
intimately connecting faith in immortality with faith in God, that
emphasized the essential difference of the immortal soul of man from
the mortal soul of the brute. In the dualistic philosophy the idea
prevailed principally through the influence of Descartes (1643);
he contended that man alone had a true "soul," and, consequently,
sensation and free will, and that the animals were mere automata, or
machines, without will or sensibility. Ever since the majority of
psychologists--including even Kant--have entirely neglected the mental
life of the brute, and restricted psychological research to man:
human psychology, mainly introspective, dispensed with the fruitful
comparative method, and so remained at that lower point of view which
human morphology took before Cuvier raised it to the position of a
"philosophic science" by the foundation of comparative anatomy.

Scientific interest in the psychic activity of the brute was revived
in the second half of the last century, in connection with the
advance of systematic zoology and physiology. A strong impulse was
given to it by the work of Reimarus: "General observations on the
instincts of animals" (Hamburg, 1760). At the same time a deeper
scientific investigation had been facilitated by the thorough reform
of physiology by Johannes Müller. This distinguished biologist, having
a comprehensive knowledge of the whole field of organic nature, of
morphology, and of physiology, introduced the "exact methods" of
observation and experiment into the whole province of physiology, and,
with consummate skill, combined them with the comparative methods. He
applied them, not only to mental life in the broader sense (to speech,
senses, and brain-action), but to all the other phenomena of life. The
sixth book of his _Manual of Human Physiology_ treats specially of the
life of the soul, and contains eighty pages of important psychological

During the last forty years a great number of works on comparative
animal psychology have appeared, principally occasioned by the great
impulse which Darwin gave in 1859 by his work on _The Origin of
Species_, and by the application of the idea of evolution to the
province of psychology. The more important of these works we owe to
Romanes and Sir J. Lubbock, in England; to W. Wundt, L. Büchner, G.
Schneider, Fritz Schultze, and Karl Groos, in Germany; to Alfred
Espinas and E. Jourdan, in France; and to Tito Vignoli, in Italy.

In Germany, Wilhelm Wundt, of Leipzig, is considered to be the ablest
living psychologist; he has the inestimable advantage over most other
philosophers of a thorough zoological, anatomical, and physiological
education. Formerly assistant and pupil of Helmholtz, Wundt had early
accustomed himself to follow the application of the laws of physics and
chemistry through the whole field of physiology, and, consequently,
in the sense of Johannes Müller, in _psychology_, as a subsection
of the latter. Starting from this point of view, Wundt published
his valuable "Lectures on human and animal psychology" in 1863. He
proved, as he himself tells us in the preface, that the theatre of
the most important psychic processes is in the "unconscious soul,"
and he affords us "a view of the mechanism which, in the unconscious
background of the soul, manipulates the impressions which arise
from the external stimuli." What seems to me, however, of special
importance and value in Wundt's work is that he "extends the law of the
persistence of force for the first time to the psychic world, and makes
use of a series of facts of electro-physiology by way of demonstration."

Thirty years afterwards (1892) Wundt published a second, much
abridged and entirely modified, edition of his work. The important
principles of the first edition are entirely abandoned in the second,
and the monistic is exchanged for a purely dualistic stand-point.
Wundt himself says in the preface to the second edition that he has
emancipated himself from the fundamental errors of the first, and
that he "learned many years ago to consider the work a sin of his
youth"; it "weighed on him as a kind of crime, from which he longed
to free himself as soon as possible." In fact, the most important
systems of psychology are completely opposed to each other in the two
editions of Wundt's famous _Observations_. In the first edition he
is purely monistic and materialistic, in the second edition purely
dualistic and spiritualistic. In the one psychology is treated as a
_physical_ science, on the same laws as the whole of physiology, of
which it is only a part; thirty years afterwards he finds psychology
to be a _spiritual_ science, with principles and objects entirely
different from those of physical science. This conversion is most
clearly expressed in his principle of psycho-physical parallelism,
according to which "every psychic event has a corresponding physical
change"; but the two are completely independent, and are not in any
natural causal connection. This complete dualism of body and soul,
of nature and mind, naturally gave the liveliest satisfaction to the
prevailing school-philosophy, and was acclaimed by it as an important
advance, especially seeing that it came from a distinguished scientist
who had previously adhered to the opposite system of monism. As I
myself continue, after more than forty years' study, in this "narrow"
position, and have not been able to free myself from it in spite of
all my efforts, I must naturally consider the "youthful sin" of the
young physiologist Wundt to be a correct knowledge of nature, and
energetically defend it against the antagonistic view of the old
philosopher Wundt.

This entire change of philosophical principles, which we find in Wundt,
as we found it in Kant, Virchow, Du Bois-Reymond, Karl Ernst Baer, and
others, is very interesting. In their youth these able and talented
scientists embrace the whole field of biological research in a broad
survey, and make strenuous efforts to find a unifying, natural basis
for their knowledge; in their later years they have found that this is
not completely attainable, and so they entirely abandon the idea. In
extenuation of these psychological metamorphoses they can, naturally,
plead that in their youth they overlooked the difficulties of the great
task, and misconceived the true goal; with the maturer judgment of age
and the accumulation of experience they were convinced of their errors,
and discovered the true path to the source of truth. On the other hand,
it is possible to think that great scientists approach their task with
less prejudice and more energy in their earlier years--that their
vision is clearer and their judgment purer; the experiences of later
years sometimes have the effect, not of enriching, but of disturbing,
the mind, and with old age there comes a gradual decay of the brain,
just as happens in all other organs. In any case, this change of views
is in itself an instructive psychological fact; because, like many
other forms of change of opinion, it shows that the highest psychic
functions are subject to profound individual changes in the course of
life, like all the other vital processes.

For the profitable construction of comparative psychology it is
extremely important not to confine the critical comparison to man
and the brute in general, but to put side by side the innumerable
gradations of their mental activity. Only thus can we attain a clear
knowledge of the long scale of psychic development which runs unbroken
from the lowest, unicellular forms of life up to the mammals, and to
man at their head. But even within the limits of our own race such
gradations are very noticeable, and the ramifications of the "psychic
ancestral tree" are very numerous. The psychic difference between the
crudest savage of the lowest grade and the most perfect specimen of
the highest civilization is colossal--much greater than is commonly
supposed. By the due appreciation of this fact, especially in the
latter half of the century, the "Anthropology of the uncivilized races"
(Waitz) has received a strong support, and comparative ethnography has
come to be considered extremely important for psychological purposes.
Unfortunately, the enormous quantity of raw material of this science
has not yet been treated in a satisfactory critical manner. What
confused and mystic ideas still prevail in this department may be seen,
for instance, in the _Völkergedanke_ of the famous traveller, Adolf
Bastian, who, though a prolific writer, merely turns out a hopeless
mass of uncritical compilation and confused speculation.

The most neglected of all psychological methods, even up to the present
day, is the evolution of the soul; yet this little-frequented path
is precisely the one that leads us most quickly and securely through
the gloomy primeval forest of psychological prejudices, dogmas, and
errors, to a clear insight into many of the chief psychic problems. As
I did in the other branch of organic evolution, I again put before the
reader the two great branches of the science which I differentiated in
1866--ontogeny and phylogeny. The ontogeny, or embryonic development,
of the soul, individual or biontic psychogeny, investigates the gradual
and hierarchic development of the soul in the individual, and seeks to
learn the laws by which it is controlled. For a great part of the life
of the mind a good deal has been done in this direction for centuries;
rational pedagogy must have set itself the task at an early date of the
theoretical study of the gradual development and formative capacity of
the young mind that was committed to it for education and formation.
Most pedagogues, however, were idealistic or dualistic philosophers,
and so they went to work with all the prejudices of the spiritualistic
psychology. It is only in the last few decades that this dogmatic
tendency has been largely superseded even in the school by scientific
methods; we now find a greater concern to apply the chief laws of
evolution even in the discussion of the soul of the child. The raw
material of the child's soul is already qualitatively determined by
_heredity_ from parents and ancestors; education has the noble task of
bringing it to a perfect maturity by intellectual instruction and moral
training--that is, by _adaptation_. Wilhelm Preyer was the first to
lay the foundation of our knowledge of the early psychic development
in his interesting work on _The Mind of the Child_. Much is still to
be done in the study of the later stages and metamorphoses of the
individual soul, and once more the correct, critical application of the
biogenetic law is proving a guiding star to the scientific mind.

A new and fertile epoch of higher development dawned for psychology
and all other biological sciences when Charles Darwin applied the
principles of evolution to them forty years ago. The seventh chapter
of his epoch-making work on _The Origin of Species_ is devoted to
instinct. It contains the valuable proof that the instincts of animals
are subject, like all other vital processes, to the general laws of
historic development. The special instincts of particular species were
formed by _adaptation_, and the modifications thus acquired were handed
on to posterity by _heredity_; in their formation and preservation
natural selection plays the same part as in the transformation of
every other physiological function. Darwin afterwards developed this
fundamental thought in a number of works, showing that the same laws of
"mental evolution" hold good throughout the entire organic world, not
less in man than in the brute, and even in the plant. Hence the unity
of the organic world, which is revealed by the common origin of its
members, applies also to the entire province of psychic life, from the
simplest unicellular organism up to man.

To George Romanes we owe the further development of Darwin's
psychology and its special application to the different sections of
psychic activity. Unfortunately, his premature decease prevented the
completion of the great work which was to reconstruct every section
of comparative psychology on the lines of monistic evolution. The
two volumes of this work which were completed are among the most
valuable productions of psychological literature. For, conformably
to the principles of our modern monistic research, his first care
was to collect and arrange all the important facts which have been
empirically established in the field of comparative psychology in the
course of centuries; in the second place, these facts are tested with
an _objective criticism_, and systematically distributed; finally, such
rational conclusions are drawn from them on the chief general questions
of psychology as are in harmony with the fundamental principles of
modern monism. The first volume of Romanes's work bears the title
of _Mental Evolution in the Animal World_; it presents, in natural
connection, the entire length of the chain of psychic evolution in the
animal world, from the simplest sensations and instincts of the lowest
animals to the elaborate phenomena of consciousness and reason in the
highest. It contains also a number of extracts from a manuscript which
Darwin left "on instinct," and a complete collection of all that he
wrote in the province of psychology.

The second and more important volume of Romanes's work treats of
"Mental evolution in man and the origin of human faculties." The
distinguished psychologist gives a convincing proof in it "that the
psychological barrier between man and the brute has been overcome."
Man's power of conceptual thought and of abstraction has been gradually
evolved from the non-conceptual stages of thought and ideation in the
nearest related mammals. Man's highest mental powers--reason, speech,
and conscience--have arisen from the lower stages of the same faculties
in our primate ancestors (the simiæ and prosimiæ). Man has no single
mental faculty which is his exclusive prerogative. His whole psychic
life differs from that of the nearest related mammals only in degree,
and not in kind; quantitatively, not qualitatively.

I recommend those of my readers who are interested in these momentous
questions of psychology to study the profound work of Romanes. I am
completely at one with him and Darwin in almost all their views and
convictions. Wherever an apparent discrepancy is found between these
authors and my earlier productions, it is either a case of imperfect
expression on my part or an unimportant difference in application of
principle. For the rest, it is characteristic of this "science of
ideas" that the most eminent philosophers hold entirely antagonistic
views on its fundamental notions.



    Psychological Unity of Organic Nature--Material Basis of the
    Soul: Psychoplasm--Scale of Sensation--Scale of Movement--Scale
    of Reflex Action--Simple and Compound Reflex Action--Reflex
    Action and Consciousness--Scale of Perception--Unconscious and
    Conscious Perception--Scale of Memory--Unconscious and Conscious
    Memory--Association of Perceptions--Instinct--Primary and Secondary
    Instincts--Scale of Reason--Language--Emotion and Passion--The
    Will--Freedom of the Will

The great progress which psychology has made, with the assistance
of evolution, in the latter half of the century culminates in the
recognition of _the psychological unity of the organic world_.
Comparative psychology, in co-operation with the ontogeny and phylogeny
of the _psyche_, has enforced the conviction that organic life in all
its stages, from the simplest unicellular protozoon up to man, springs
from the same elementary forces of nature, from the physiological
functions of sensation and movement. The future task of scientific
psychology, therefore, is not, as it once was, the exclusively
subjective and introspective analysis of the highly developed mind
of a philosopher, but the objective, comparative study of the long
gradation by which man has slowly arisen through a vast series of lower
animal conditions. This great task of separating the different steps
in the psychological ladder, and proving their unbroken phylogenetic
connection, has only been seriously attempted during the last ten
years, especially in the splendid work of Romanes. We must confine
ourselves here to a brief discussion of a few of the general questions
which that gradation has suggested.

All the phenomena of the psychic life are, without exception, bound
up with certain material changes in the living substance of the body,
the _protoplasm_. We have given to that part of the protoplasm which
seems to be the indispensable substratum of psychic life the name
of _psychoplasm_ (the "soul-substance," in the monistic sense); in
other words, we do not attribute any peculiar "essence" to it, but
we consider the _psyche_ to be merely _a collective idea of all the
psychic functions of protoplasm_. In this sense the "soul" is merely
a physiological abstraction like "assimilation" or "generation." In
man and the higher animals, in accordance with the division of labor
of the organs and tissues, the psychoplasm is a differentiated part of
the nervous system, the _neuroplasm_ of the ganglionic cells and their
fibres. In the lower animals, however, which have no special nerves
and organs of sense, and in the plants, the psychoplasm has not yet
reached an independent differentiation. Finally, in the unicellular
protists, the psychoplasm is identified either with the whole of the
living protoplasm of the simple cell or with a portion of it. In all
cases, in the lowest as well as the highest stages of the psychological
hierarchy, a certain chemical composition and a certain physical
activity of the psychoplasm are indispensable before the "soul" can
function or act. That is equally true of the elementary psychic
function of the plasmatic sensation and movement of the protozoa,
and of the complex functions of the sense-organs and the brain in the
higher animals and man. The activity of the psychoplasm, which we call
the "soul," is always connected with metabolism.

All living organisms, without exception, are sensitive; they are
influenced by the condition of their environment, and react thereon by
certain modifications in their own structure. Light and heat, gravity
and electricity, mechanical processes and chemical action in the
environment, act as _stimuli_ on the sensitive psychoplasm, and effect
changes in its molecular composition. We may distinguish the following
five chief stages of this sensibility:

I. At the lowest stage of organization the _whole psychoplasm_, as
such, is sensitive, and reacts on the stimuli from without; that is the
case with the lowest protists, with many plants, and with some of the
most rudimentary animals.

II. At the second stage very simple and undiscriminating _sense-organs_
begin to appear on the surface of the organism, in the form of
protoplasmic filaments and pigment spots, the forerunners of the nerves
of touch and the eyes; these are found in some of the higher protists
and in many of the lower animals and plants.

III. At the third stage _specific organs_ of sense, each with a
peculiar adaptation, have arisen by differentiation out of these
rudimentary processes: there are the chemical instruments of smell
and taste, and the physical organs of touch, temperature, hearing,
and sight. The "specific energy" of these sense-organs is not an
original inherent property of theirs, but has been gained by functional
adaptation and progressive heredity.

IV. The fourth stage is characterized by the _centralization_ or
integration of the _nervous system_, and, consequently, of sensation;
by the association of the previously isolated or localized sensations
presentations arise, though they still remain unconscious. That is the
condition of many both of the lower and the higher animals.

V. Finally, at the fifth stage, the highest psychic function,
_conscious perception_, is developed by the mirroring of the sensations
in a central part of the nervous system, as we find in man and the
higher vertebrates, and probably in some of the higher invertebrates,
notably the articulata.

All living organisms without exception have the faculty of _spontaneous
movement_, in contradistinction to the rigidity and inertia of
unorganized substances (_e.g._, crystals); in other words, certain
changes of place of the particles occur in the living psychoplasm
from internal causes, which have their source in its own chemical
composition. These active vital movements are partly discovered by
direct observation and partly only known indirectly, by inference from
their effects. We may distinguish five stages of them.

I. At the lowest stage of organic life, in the chromacea, and many
protophyta and lower metaphyta, we perceive only those _movements of
growth_ which are common to all organisms. They are usually so slow
that they cannot be directly observed; they have to be inferred from
their results--from the change in size and form of the growing organism.

II. Many protists, particularly unicellular algæ of the groups of
diatomacea and desmidiacea, accomplish a kind of creeping or swimming
motion by _secretion_, by ejecting a slimy substance at one side.

III. Other organisms which float in water--for instance, many of the
radiolaria, siphonophora, ktenophora, and others--ascend and descend by
altering their _specific gravity_, sometimes by osmosis, sometimes by
the separation or squeezing-out of air.

IV. Many plants, especially the sensitive plants (mimosa) and other
papilionacea, effect movements of their leaves or other organs by
_change of pressure_--that is, they alter the strain of the protoplasm,
and, consequently, its pressure on the enclosing elastic walls of the

V. The most important of all organic movements are the _phenomena
of contraction_--_i.e._, changes of form at the surface of the
organism, which are dependent on a twofold displacement of their
elements; they always involve two different conditions or phases
of motion--contraction and expansion. Four different forms of this
plasmatic contraction may be enumerated:

    (_a_) Amoeboid movement (in rhizopods, blood-cells,
    pigment-cells, etc.).

    (_b_) A similar flow of protoplasm within enclosed cells.

    (_c_) Vibratory motion (ciliary movements) in infusoria,
    spermatozoa, ciliated epithelial cells.

    (_d_) Muscular movement (in most animals).

The elementary psychic activity that arises from the combination of
sensation and movement is called _reflex_ (in the widest sense),
reflective function, or _reflex action_. The movement--no matter what
kind it is--seems in this case to be the immediate result of the
_stimulus_ which evoked the sensation; it has, on that account, been
called stimulated motion in its simplest form (in the protists). All
living protoplasm has this feature of irritability. Any physical or
chemical change in the environment may, in certain circumstances,
act as a stimulus on the psychoplasm, and elicit or "release" a
movement. We shall see later on how this important physical concept of
"releasing" directly connects the simplest organic reflex actions with
similar mechanical phenomena of movement in the inorganic world (for
instance, in the explosion of powder by a spark, or of dynamite by a
blow). We may distinguish the following seven stages in the scale of
reflex action:

I. At the lowest stage of organization, in the lowest protists, the
stimuli of the outer world (heat, light, electricity, etc.) cause in
the indifferent protoplasm only those indispensable movements of growth
and nutrition which are common to all organisms, and are absolutely
necessary for their preservation. That is also the case in most of the

II. In the case of many freely moving protists (especially the
amoeba, the heliozoon, and the rhizopod) the stimuli from without
produce on every spot of the unprotected surface of the unicellular
organism external movements which take the form of changes of shape,
and sometimes changes of place (amoeboid movement, pseudopod
formation, the extension and withdrawal of what look like feet); these
indefinite, variable processes of the protoplasm are not yet permanent
organs. In the same way, general organic irritability takes the form
of indeterminate reflex action in the sensitive plants and the lowest
metazoa; in many multicellular organisms the stimuli may be conducted
from one cell to another, as all the cells are connected by fine fibres.

III. Many protists, especially the more highly developed protozoa,
produce on their unicellular body two little organs of the simplest
character--an organ of touch and an organ of movement. Both these
instruments are direct external projections of protoplasm; the
stimulus, which alights on the first, is immediately conducted to
the other by the psychoplasm of the unicellular body, and causes it
to contract. This phenomenon is particularly easy to observe, and
even produce experimentally, in many of the stationary infusoria
(for instance, the _poteriodendron_ among the flagellata, and the
_vorticella_ among the ciliata). The faintest stimulus that touches the
extremely sensitive hairs, or _cilia_, at the free end of the cells,
immediately causes a contraction of a thread-like stalk at the other,
fixed end. This phenomenon is known as a "simple reflex arch."

IV. These phenomena of the unicellular organism of the infusoria lead
on to the interesting mechanism of the neuro-muscular cells, which we
find in the multicellular body of many of the lower metazoa, especially
in the cnidaria (polyps and corals). Each single neuro-muscular cell
is a "unicellular reflex organ"; it has on its surface a sensitive
spot, and a motor muscular fibre inside at the opposite end; the latter
contracts as soon as the former is stimulated.

V. In other cnidaria, notably in the free swimming medusæ--which are
closely related to the stationary polyps--the simple neuro-muscular
cell becomes two different cells, connected by a filament; an external
_sense-cell_ (in the outer skin) and an internal _muscular cell_ (under
the skin). In this _bicellular reflex organ_ the one cell is the
rudimentary organ of sensation, the other of movement; the connecting
bridge of the psychoplasmic filament conducts the stimulus from one to
the other.

VI. The most important step in the gradual construction of the reflex
mechanism is the division into three cells; in the place of the simple
connecting bridge we spoke of there appears a third independent cell,
the _soul-cell_, or ganglionic cell; with it appears also a new psychic
function, _unconscious presentation_, which has its seat in this
cell. The stimulus is first conducted from the sensitive cell to this
intermediate presentative or psychic cell, and then issued from this to
the motor muscular cell as a mandate of movement. These _tricellular
reflex organs_ are preponderantly developed in the great majority of
the invertebrates.

VII. Instead of this arrangement we find in most of the vertebrates
a _quadricellular reflex organ_, two distinct "soul-cells," instead
of one, being inserted between the sensitive cell and the motor cell.
The external stimulus, in this case, is first conducted centripetally
to the sensitive cell (the sensible psychic cell), from this to the
_will-cell_ (the motor psychic cell), and from this, finally, to the
contractile muscular cell. When many such reflex organs combine and new
psychic cells are interposed we have the intricate reflex mechanism of
man and the higher vertebrates.

The important distinction which we make, in morphology and physiology,
between unicellular and multicellular organisms holds good for their
elementary psychic activity, reflex action. In the unicellular
protists (both the plasmodomous primitive plants, or _protophyta_,
and the plasmophagous primitive animals, or _protozoa_) the whole
physical process of reflex action takes place in the protoplasm of
one single cell; their "cell-soul" seems to be a unifying function
of the psychoplasm of which the various phases only begin to be seen
separately when the differentiation of special organs sets in.

The second stage of psychic activity, compound reflex action, begins
with the cenobitic protists (_v.g._, the volvox and the carchesium).
The innumerable social cells, which make up this cell-community
or coenobium, are always more or less connected, often directly
connected by filamentous bridges of protoplasm. A stimulus that alights
on one or more cells of the community is communicated to the rest by
means of the connecting fibres, and may produce a general contraction.
This connection is found, also, in the tissues of the multicellular
animals and plants. It was erroneously believed at one time that the
cells of vegetal tissue were completely isolated from each other, but
we have now discovered fine filaments of protoplasm throughout, which
penetrate the thick membranes of the cells, and maintain a material
and psychological communication between their living plasmic contents.
That is the explanation of the mimosa: when the tread of the passer-by
shakes the root of the plant, the stimulus is immediately conveyed to
all the cells, and causes a general contraction of its tender leaves
and a drooping of the stems.

An important and universal feature of all reflex phenomena is the
absence of consciousness. For reasons which we shall give in the tenth
chapter we only admit the presence of consciousness in man and the
higher animals, not in plants, the lower animals, and the protists;
consequently all stimulated movements in the latter must be regarded
as reflex--that is, all movements which are not _spontaneous_, not the
outcome of internal causes (impulsive and automatic movements).[14]
It is different with the higher animals which have developed a
centralized nervous system and elaborate sense-organs. In these cases
consciousness has been gradually evolved from the psychic reflex
activity, and now conscious, voluntary action appears, in opposition to
the still continuing reflex action below. However, we must distinguish
two different processes, as we did in the question of instinct--primary
and secondary reflex action. Primary reflex actions are those which
have never reached the stage of consciousness in phyletic development,
and thus preserve the primitive character (by heredity from lower
animal forms). Secondary reflex actions are those which were conscious,
voluntary actions in our ancestors, but which afterwards became
unconscious from habit or the lapse of consciousness. It is impossible
to draw a hard and fast line in such cases between conscious and
unconscious psychic function.

Older psychologists (Herbart, for instance) considered "presentation"
to be the fundamental psychic phenomenon, from which all the others are
derived. Modern comparative psychology endorses this view in so far as
it relates to the idea of _unconscious_ presentation; but it considers
_conscious_ presentation to be a secondary phenomenon of mental life,
which is entirely wanting in plants and the lower animals, and is
only developed in the higher animals. Among the many contradictory
definitions which psychologists have given of "presentation," we think
the best is that which makes it consist in an internal picture of the
external object which is given us in sensation--an "idea," in the
broader sense. We may distinguish the following four stages in the
rising scale of presentative function:

I. _Cellular presentation._--At the lowest stages we find presentation
to be a general physiological property of psychoplasm; even in the
simplest unicellular protist sensations may leave a permanent trace in
the psychoplasm, and these may be reproduced by memory. In more than
four thousand kinds of radiolaria, which I have described, every single
species is distinguished by special, hereditary skeletal structure. The
construction of this specific, and often highly elaborate, skeleton
by a cell of the simplest description (generally globular) is only
intelligible when we attribute the faculty of presentation, and,
indeed, of a special reproduction of the plastic "feeling of distance,"
to the constructive protoplasm--as I have pointed out in my _Psychology
of the Radiolaria_.[15]

II. _Histionic presentation._--In the coenobia or cell-colonies of
the social protists, and still better in the tissues of plants and
lower, nerveless animals (sponges, polyps, etc.), we find the second
stage of unconscious presentation, which consists of the common psychic
activity of a number of closely connected cells. If a single stimulus
may, instead of simply spending itself in the reflex movement of an
organ (the leaf of a plant, for instance, or the arm of a polyp),
leave a permanent impression, which can be spontaneously reproduced
later on, we are bound to assume, in explaining the phenomenon, a
histionic presentation, dependent on the psychoplasm of the associated

III. _Unconscious presentation in the ganglionic cells._--This
third and higher stage of presentation is the commonest form the
function takes in the animal world; it seems to be a localization of
presentation in definite "soul-cells." In its simplest form it appears
at the sixth stage of reflex action, when the tricellular reflex organ
arises: the seat of presentation is then the intermediate psychic
cell, which is interposed between the sensitive cell and the muscular
cell. With the increasing development of the animal nervous system
and its progressive differentiation and integration, this unconscious
presentation also rises to higher stages.

IV. _Conscious presentation in the cerebral cells._--With the highest
stage of development of the animal organization consciousness arises,
as a special function of a certain central organ of the nervous
system. As the presentations are conscious, and as special parts of
the brain arise for the association of these conscious presentations,
the organism is qualified for those highest psychic functions which
we call thought and reflection, intellect and reason. Although the
tracing of the phyletic barrier between the older, unconscious, and the
younger, conscious, presentation is extremely difficult, we can affirm,
with some degree of probability, that the evolution of the latter from
the former was _polyphyletic_; because we find conscious and rational
thought, not only in the highest forms of the vertebrate stem (man,
mammals, birds, and a part of the lower vertebrates), but also in the
most highly developed representatives of other animal groups (ants
and other insects, spiders and the higher crabs among the articulata,
cephalopods among the mollusca).

The evolutionary scale of memory is closely connected with that of
presentation; this extremely important function of the psychoplasm--the
condition of all further psychic development--consists essentially
in the _reproduction of presentations_. The impressions in the
bioplasm, which the stimulus produced as sensations, and which
became presentations in remaining, are revived by memory; they pass
from potentiality to actuality. The latent potential energy of the
psychoplasm is transformed into kinetic energy. We may distinguish
four stages in the upward development of memory, corresponding to the
four stages of presentation.

I. _Cellular memory._--Thirty years ago Ewald Hering showed "memory to
be a general property of organized matter" in a thoughtful work, and
indicated the great significance of this function, "to which we owe
almost all that we are and have." Six years later, in my work on _The
Perigenesis of the Plastidule, or the Undulatory Origin of the Parts
of Life: an Experiment in the Mechanical Explanation of Elementary
Evolutionary Processes_, I developed these ideas, and endeavored
to base them on the principles of evolution. I have attempted to
show in that work that unconscious memory is a universal and very
important function of all _plastidules_; that is, of those hypothetical
molecules, or groups of molecules, which Naegeli has called _micellae_,
others _bioplasts_, and so forth. Only _living_ plastidules, as
individual molecules of the active protoplasm, are reproductive,
and so gifted with memory; that is the chief difference between the
organic and inorganic worlds. It might be stated thus: "Heredity is
the memory of the plastidule, while variability is its comprehension."
The elementary memory of the unicellular protist is made up of the
molecular memory of the plastidules or _micellae_, of which its living
cell-body is constructed. As regards the extraordinary performances
of unconscious memory in these unicellular protists, nothing could be
more instructive than the infinitely varied and regular formation of
their defensive apparatus, their shells and skeletons; in particular,
the diatomes and cosmaria among the protophytes, and the radiolaria
and thalamophora among the protozoa, afford an abundance of most
interesting illustrations. In many thousand species of these protists
the specific form which is inherited is _relatively constant_, and
proves the fidelity of their unconscious cellular memory.

II. _Histionic memory._--Equally interesting examples of the second
stage of memory, the unconscious memory of tissues, are found in the
heredity of the individual organs of plants and the lower, nerveless
animals (sponges, etc.). This second stage seems to be _a reproduction
of the histionic presentations_, that association of cellular
presentations which sets in with the formation of coenobia in the
social protists.

III. In the same way we must regard the third stage, the unconscious
memory of those animals which have a nervous system, as a reproduction
of the corresponding "unconscious presentations" which are stored up
in certain ganglionic cells. In most of the lower animals all memory
is unconscious. Moreover, even in man and the higher animals, to whom
we must ascribe consciousness, the daily acts of unconscious memory
are much more numerous and varied than those of the conscious faculty;
we shall easily convince ourselves of that if we make an impartial
study of a thousand unconscious acts we perform daily out of habit, and
without thinking of them, in walking, speaking, writing, eating, and so

IV. Conscious memory, which is the work of certain brain-cells in
man and the higher animals, is an "internal mirroring" of very late
development, the highest outcome of the same psychic reproduction of
presentations which were mere unconscious processes in the ganglionic
cells of our lower animal ancestors.

The concatenation of presentations--usually called the association of
ideas--also runs through a long scale, from the lowest to the highest
stages. This, too, is originally and predominantly unconscious
("instinct"); only in the higher classes of animals does it gradually
become conscious ("reason"). The psychic results of this "association
of ideas" are extremely varied; still, a very long, unbroken line of
gradual development connects the simplest unconscious association of
the lowest protist with the elaborate conscious chain of ideas of the
civilized man. The _unity of consciousness_ in man is given as its
highest consequence (Hume, Condillac). All higher mental activity
becomes more perfect in proportion as the normal association extends
to more numerous presentations, and in proportion to the order which
is imposed on them by the "criticism of pure reason." In dreams,
where this criticism is absent, the association of the reproduced
impressions often takes the wildest forms. Even in the work of the
poetic imagination, which constructs new groups of images by varying
the association of the impressions received, and in hallucinations,
etc., they are often most unnaturally arranged, and seem to the
prosaic observer to be perfectly irrational. This is especially true
of supernatural "forms of belief," the apparitions of spiritism,
and the fantastic notions of the transcendental dualist philosophy;
though it is precisely these _abnormal associations_ of "faith" and of
"revelation" that have often been deemed the greatest treasures of the
human mind (cf. chap. xvi.).

The antiquated psychology of the Middle Ages (which, however, still
numbers many adherents) considered the mental life of man and that
of the brute to be two entirely different phenomena; the one it
attributed to "reason," the other to "instinct." In harmony with the
traditional story of creation, it was assumed that each animal species
had received a definite, unconscious psychic force from the Creator
at its formation, and that this instinct of each species was just as
unchangeable as its bodily structure. Lamarck proved the untenableness
of this error in 1809 by establishing the theory of Descent, and Darwin
completely demolished it in 1859. He proved the following important
theses with the aid of his theory of selection:

1. The instincts of species show individual differences, and are
just as subject to modification under the law of _adaptation_ as the
morphological features of their bodily structure.

2. These modifications (generally arising from a change of habits) are
partly transmitted to offspring by _heredity_, and thus accumulate and
are accentuated in the course of generations.

3. _Selection_, both artificial and natural, singles out certain of
these inherited modifications of the psychic activity; it preserves the
most useful and rejects the least adaptive.

4. The _divergence_ of psychic character which thus arises leads, in
the course of generations, to the formation of new instincts, just as
the divergence of morphological character gives rise to new species.

Darwin's theory of instinct is now accepted by most biologists; Romanes
has treated it so ably, and so greatly expanded it in his distinguished
work on _Mental Evolution in the Animal World_, that I need merely
refer to it here. I will only venture the brief statement that, in my
opinion, there are instincts in _all_ organisms--in all the protists
and plants as well as in all the animals and in man; though in the
latter they tend to disappear in proportion as reason makes progress at
their expense.

The two chief classes of instincts to be differentiated are the
primary and secondary. Primary instincts are the common lower
impulses which are unconscious and inherent in the psychoplasm
from the commencement of organic life; especially the impulses to
self-preservation (by defence and maintenance) and to the preservation
of the species (by generation and the care of the young). Both these
fundamental instincts of organic life, _hunger_ and _love_, sprang
up originally in perfect unconsciousness, without any co-operation
of the intellect or reason. It is otherwise with the _secondary_
instincts. These were due originally to an intelligent adaptation, to
rational thought and resolution, and to purposive conscious action.
Gradually, however, they became so automatic that this "other nature"
acted unconsciously, and, even through the action of heredity, seemed
to be "innate" in subsequent generations. The consciousness and
deliberation which originally accompanied these particular instincts
of the higher animals and man have died away in the course of the
life of the plastidules (as in "abridged heredity"). The unconscious
purposive actions of the higher animals (for instance, their mechanical
instincts) thus come to appear in the light of innate impulses. We have
to explain in the same way the origin of the "_à priori_ ideas" of man;
they were originally formed empirically by his predecessors.[16]

In the superficial psychological treatises which ignore the mental
activity of animals and attribute to man only a "true soul," we
find him credited also with the exclusive possession of reason and
consciousness. This is another trivial error (still to be found in many
a manual, nevertheless) which the comparative psychology of the last
forty years has entirely dissipated. The higher vertebrates (especially
those mammals which are most nearly related to man) have just as good a
title to "reason" as man himself, and within the limits of the animal
world there is the same long chain of the gradual development of
reason as in the case of humanity. The difference between the reason
of a Goethe, a Kant, a Lamarck, or a Darwin, and that of the lowest
savage, a Veddah, an Akka, a native Australian, or a Patagonian, is
much greater than the graduated difference between the reason of the
latter and that of the most "rational" mammals, the anthropoid apes, or
even the papiomorpha, the dog, or the elephant. This important thesis
has been convincingly proved by the thoroughly critical comparative
work of Romanes and others. We shall not, therefore, attempt to cover
that ground here, nor to enlarge on the distinction between the reason
and the intellect; as to the meaning and limits of these concepts
philosophic experts give the most contradictory definitions, as they do
on so many other fundamental questions of psychology. In general it may
be said that the process of the formation of concepts, which is common
to both these cerebral functions, is confined to the narrower circle of
concrete, proximate associations in the intellect, but reaches out to
the wider circle of abstract, more comprehensive groups of associations
in the work of reason. In the long gradation which connects the reflex
actions and the instincts of the lower animals with the reason of the
highest, intellect precedes the latter. And there is the fact, of
great importance to our whole psychological treatise, that even these
highest of our mental faculties are just as much subject to the laws
of heredity and adaptation as are their respective organs; Flechsig
pointed out in 1894 that the "organs of thought," in man and the higher
mammals, are those parts of the cortex of the brain which lie between
the four inner sense-centres (cf. chapters x. and xi.).

The higher grade of development of ideas, of intellect and reason,
which raises man so much above the brute, is intimately connected with
the rise of language. Still here also we have to recognize a long chain
of evolution which stretches unbroken from the lowest to the highest
stages. Speech is no more an exclusive prerogative of man than reason.
In the wider sense, it is a common feature of all the higher gregarious
animals, at least of all the articulata and the vertebrates, which live
in communities or herds; they need it for the purpose of understanding
each other and communicating their impressions. This is effected either
by touch or by signs, or by sounds having a definite meaning. The
song of the bird or of the anthropoid ape (_hylobates_), the bark of
the dog, the neigh of the horse, the chirp of the cricket, the cry of
the cicada, are all specimens of animal speech. Only in man, however,
has that articulate conceptual speech developed which has enabled his
reason to attain such high achievements. Comparative philology, one
of the most interesting sciences that has arisen during the century,
has shown that the numerous elaborate languages of the different
nations have been slowly and gradually evolved from a few simple
primitive tongues (Wilhelm Humboldt, Bopp, Schleicher, Steinthal, and
others). August Schleicher, of Jena, in particular, has proved that
the historical development of language takes place under the same
phylogenetic laws as the evolution of other physiological faculties
and their organs. Romanes (1893) has expanded this proof, and amply
demonstrated that human speech, also, differs from that of the brute
only in _degree_ of development, not in essence and kind.

The important group of psychic activities which we embrace under the
name of "emotion" plays a conspicuous part both in theoretical and
practical psychology. From our point of view they have a peculiar
importance from the fact that we clearly see in them the direct
connection of cerebral functions with other physiological functions
(the beat of the heart, sense-action, muscular movement, etc.);
they, therefore, prove the unnatural and untenable character of
the philosophy which would essentially dissociate psychology from
physiology. All the external expressions of emotional life which we
find in man are also present in the higher animals (especially in the
anthropoid ape and the dog); however varied their development may be,
they are all derived from the two elementary functions of the _psyche_,
sensation and motion, and from their combination in reflex action and
presentation. To the province of sensation, in a wide sense, we must
attribute the feeling of _like_ and _dislike_ which determines the
emotion; while the corresponding _desire_ and _aversion_ (love and
hatred), the effort to attain what is liked and avoid what is disliked,
belong to the category of movement. "Attraction" and "repulsion"
seem to be the sources of _will_, that momentous element of the soul
which determines the character of the individual. The _passions_,
which play so important a part in the psychic life of man, are but
intensifications of emotion. Romanes has recently shown that these also
are common to man and the brute. Even at the lowest stage of organic
life we find in all the protists those elementary feelings of like
and dislike, revealing themselves in what are called their _tropisms_,
in the striving after light and darkness, heat or cold, and in their
different relations to positive and negative electricity. On the other
hand, we find at the highest stage of psychic life, in civilized man,
those finer shades of emotion, of delight and disgust, of love and
hatred, which are the mainsprings of civilization and the inexhaustible
sources of poetry. Yet a connecting chain of all conceivable gradations
unites the most primitive elements of feeling in the psychoplasm of the
unicellular protist with the highest forms of passion that rule in the
ganglionic cells of the cortex of the human brain. That the latter are
absolutely amenable to physical laws was proved long ago by the great
Spinoza in his famous _Statics of Emotion_.

The notion of _will_ has as many different meanings and definitions
as most other psychological notions--presentation, soul, mind, and
so forth. Sometimes will is taken in the widest sense as a _cosmic
attribute_, as in the "World as will and presentation" of Schopenhauer;
sometimes it is taken in its narrowest sense as an _anthropological
attribute_, the exclusive prerogative of man--as Descartes taught, for
instance, who considered the brute to be a mere machine, without will
or sensation. In the ordinary use of the term, _will_ is derived from
the phenomenon of voluntary movement, and is thus regarded as a psychic
attribute of most animals. But when we examine the will in the light of
comparative physiology and evolution, we find--as we do in the case of
sensation--that it is a universal property of living psychoplasm. The
automatic and the reflex movements which we observe everywhere, even
in the unicellular protists, seem to be the outcome of inclinations
which are inseparably connected with the very idea of life. Even in the
plants and lowest animals these inclinations, or tropisms, seem to be
the joint outcome of the inclinations of all the combined individual

But when the "tricellular reflex organ" arises (page 115), and a third
independent cell--the "psychic," or "ganglionic," cell--is interposed
between the sense-cell and the motor cell, we have an independent
elementary organ of will. In the lower animals, however, this will
remains _unconscious_. It is only when consciousness arises in the
higher animals, as the subjective mirror of the objective, though
internal, processes in the neuroplasm of the psychic cells, that the
will reaches that highest stage which likens it in character to the
human will, and which, in the case of man, assumes in common parlance
the predicate of "liberty." Its free dominion and action become more
and more deceptive as the muscular system and the sense-organs develop
with a free and rapid locomotion, entailing a correlative evolution of
the brain and the organs of thought.

The question of the liberty of the will is the one which has more than
any other cosmic problem occupied the time of thoughtful humanity,
the more so that in this case the great philosophic interest of the
question was enhanced by the association of most momentous consequences
for practical philosophy--for ethics, education, law, and so forth.
Emil du Bois-Reymond, who treats it as the seventh and last of his
"seven cosmic problems," rightly says of the question: "Affecting
everybody, apparently accessible to everybody, intimately involved in
the fundamental conditions of human society, vitally connected with
religious belief, this question has been of immeasurable importance
in the history of civilization. There is probably no other object
of thought on which the modern library contains so many dusty folios
that will never again be opened." The importance of the question is
also seen in the fact that Kant put it in the same category with the
questions of the immortality of the soul and belief in God. He called
these three great questions the indispensable "postulates of practical
reason," though he had already clearly shown them to have no reality
whatever in the light of _pure_ reason.

The most remarkable fact in connection with this fierce and confused
struggle over the freedom of the will is, perhaps, that it has been
theoretically rejected, not only by the greatest critical philosophers,
but even by their extreme opponents, and yet it is still affirmed to
be self-evident by the majority of people. Some of the first teachers
of the Christian Churches--such as St. Augustine and Calvin--rejected
the freedom of the will as decisively as the famous leaders of pure
materialism, Holbach in the eighteenth and Büchner in the nineteenth
century. Christian theologians deny it, because it is irreconcilable
with their belief in the omnipotence of God and in predestination. God,
omnipotent and omniscient, saw and willed all things from eternity--he
must, consequently, have predetermined the conduct of man. If man, with
his free will, were to act otherwise than God had ordained, God would
not be all-mighty and all-knowing. In the same sense Leibnitz, too,
was an unconditional determinist. The monistic scientists of the last
century, especially Laplace, defended determinism as a consequence of
their mechanical view of life.

The great struggle between the determinist and the indeterminist,
between the opponent and the sustainer of the freedom of the will,
has ended to-day, after more than two thousand years, completely in
favor of the determinist. The human will has no more freedom than that
of the higher animals, from which it differs only in degree, not in
kind. In the last century the dogma of liberty was fought with general
philosophic and cosmological arguments. The nineteenth century has
given us very different weapons for its definitive destruction--the
powerful weapons which we find in the arsenal of comparative physiology
and evolution. We now know that each act of the will is as fatally
determined by the organization of the individual and as dependent on
the momentary condition of his environment as every other psychic
activity. The character of the inclination was determined long ago
by _heredity_ from parents and ancestors; the determination to each
particular act is an instance of _adaptation_ to the circumstances of
the moment wherein the strongest motive prevails, according to the laws
which govern the statics of emotion. Ontogeny teaches us to understand
the evolution of the will in the individual child. Phylogeny reveals
to us the historical development of the will within the ranks of our
vertebrate ancestors.



    Importance of Ontogeny to Psychology--Development of the
    Child-Soul--Commencement of Existence of the Individual
    Soul--The Storing of the Soul--Mythology of the Origin of
    the Soul--Physiology of the Origin of the Soul--Elementary
    Processes in Conception--Coalescence of the Ovum and
    the Spermatozoon--Cell-Love--Heredity of the Soul from
    Parents and Ancestors--Its Physiological Nature as the
    Mechanics of the Protoplasm--Blending of Souls (Psychic
    Amphigony)--Reversion, Psychological Atavism--The Biogenetic
    Law in Psychology--Palingenetic Repetition and Cenogenetic
    Modification--Embryonic and Post-Embryonic Psychogeny

The human soul--whatever we may hold as to its nature--undergoes
a continual development throughout the life of the individual.
This ontogenetic fact is of fundamental importance in our monistic
psychology, though the "professional" psychologists pay little or no
attention to it. Since the embryology of the individual is, on Baer's
principle--and in accordance with the universal belief of modern
biologists--the "true torch-bearer for all research into the organic
body," it will afford us a reliable light on the momentous problems of
its psychic activity.

Although, however, this "embryology of the soul" is so important and
interesting, it has hitherto met with the consideration it deserves
only within a very narrow circle. Until recently teachers were almost
the only ones to occupy themselves with a part of the problem;
since their avocation compelled them to assist and supervise the
formation of the psychic activity in the child, they were bound to
take a theoretical interest, also, in the psychogenetic facts that
came under their notice. However, these teachers, for the most part,
both in recent and in earlier times, were dominated by the current
dualistic psychology--in so far as they reflected at all; and they were
totally ignorant of the important facts of comparative psychology, and
unacquainted with the structure and function of the brain. Moreover,
their observations only extended to children in their school-days, or
in the years immediately preceding. The remarkable phenomena which
the individual psychogeny of the child offers in its earliest years,
and which are the joy and admiration of all thoughtful parents, were
scarcely ever made the subject of serious scientific research. Wilhelm
Preyer was the pioneer of this study in his interesting work on _The
Mind of the Child_ (1881). To obtain a perfectly clear knowledge of the
matter, however, we must go further back still; we must commence at the
first appearance of the soul in the impregnated ovum.

The origin of the human individual--body and soul--was still wrapped
in complete mystery at the beginning of the nineteenth century. Caspar
Friedrich Wolff had, it is true, discovered the true character of
embryonic development in 1759, in his _theoria generationis_, and
proved with the confidence of a critical observer that there is a
true _epigenesis_--_i.e._, a series of very remarkable formative
processes--in the evolution of the foetus from the simple ovum. But
the physiologists of the time, with the famous Albert Haller at their
head, flatly refused to entertain these empirical truths, which may be
directly proved by microscopic observation, and clung to the old dogma
of "preformation." This theory assumed that in the human ovum--and in
the egg of all other animals--the organism was already present, or
"preformed," in all its parts; the "evolution" of the embryo consisted
literally in an "unfolding" (_evolutio_) of the folded organs. One
curious consequence of this error was the theory of _scatulation_,
which we have mentioned on p. 55; since the ovary had to be admitted to
be present in the embryo of the woman, it was also necessary to suppose
that the germs of the next generation were already formed in it, and
so on _in infinitum_. Opposed to this dogma of the "Ovulists" was
the equally erroneous notion of the "Animalculists"; the latter held
that the germ was not really in the female ovum, but in the paternal
element, and that the store of succeeding generations was to be sought
in the spermatozoa.

Leibnitz consistently applied this theory of scatulation to the human
soul; he denied that either soul or body had a real development
(_epigenesis_), and said in his _Theodicy_: "Thus I consider that the
souls which are destined one day to become human exist in the seed,
like those of other species; that they have existed in our ancestors
as far back as Adam--that is, since the beginning of the world--in
the forms of organized bodies." Similar notions prevailed in biology
and philosophy until the third decade of the present century, when
the reform of embryology by Baer gave them their death blow. In the
province of psychology, however, they still find many adherents; they
form one group of the many curious mystical ideas which give us a
living illustration of the ontogeny of the soul.

The more accurate knowledge which we have recently obtained, through
comparative ethnology, of the various forms of myths of ancient and
modern uncivilized races, is also of great interest in psychogeny.
Still, it would take us too far from our purpose if we were to enter
into it with any fulness here; we must refer the reader to Adalbert
Svoboda's excellent work on _Forms of Faith_ (1897). In respect of
their scientific and poetical contents, we may arrange all pertinent
_psychogenetic myths_ in the following five groups:

I. The myth of transmigration.--The soul lived formerly in the body of
another animal, and passed from this into a human body. The Egyptian
priests, for instance, taught that the human soul wandered through all
the species of animals after the death of the body, returning to a
human frame after three thousand years of transmigration.

II. The myth of the in-planting of the soul.--The soul existed
independently in another place--a psychogenetic store, as it were (in a
kind of embryonic slumber or latent life); it was taken out by a bird
(sometimes represented as an eagle, generally as a white stork), and
implanted in the human body.

III. The myth of the creation of the soul.--God creates the souls,
and keeps them stored--sometimes in a pond (living in the form of
_plankton_), according to other myths in a tree (where they are
conceived as the fruit of a phanerogam); the Creator takes them from
the pond or tree, and inserts them in the human germ during the act of

IV. The myth of the scatulation of the soul (the theory of Leibnitz
which we have given above).

V. The myth of the division of the soul (the theory of Rudolph Wagner
[1855] and of other physiologists).--In the act of procreation a
portion is detached from both the (immaterial) souls of the parents;
the maternal contribution passes in the ovum, the paternal in the
spermatozoa; when these two germinal cells coalesce, the two psychic
fragments that accompany them also combine to form a new (immaterial)

Although the poetic fancies we have mentioned as to the origin of
the individual human soul are still widely accepted, their purely
mythological character is now firmly established. The deeply
interesting and remarkable research which has been made in the course
of the last twenty-five years into the more minute processes of the
impregnation and germination of the ovum has made it clear that these
mysterious phenomena belong entirely to the province of cellular
physiology (cf. p. 48). Both the female element, the ovum, and the male
fertilizing body, the sperma or spermatozoa, are _simple cells_. These
living cells possess a certain sum of physiological properties to which
we give the title of the "cell-soul," just as we do in the permanently
unicellular protist (see p. 48). Both germinal cells have the faculty
of movement and sensation. The young ovum, or egg-cell, moves after
the manner of an amoeba; the minute spermatozoa, of which there are
millions in every drop of the seminal fluid, are ciliated cells, and
swim about as freely in the sperm, by means of their lashes or _cilia_,
as the ordinary ciliated infusoria (the flagellata).

When the two cells meet as a result of copulation, or when they are
brought into contact through artificial fertilization (in the fishes,
for instance), they attract each other and become firmly attached. The
main cause of this cellular attraction is a chemical sensitive action
of the protoplasm, allied to smell or taste, which we call "erotic
chemicotropism"; it may also be correctly (both in the chemical and
the romantic sense) termed "cellular affinity" or "sexual cell-love."
A number of the ciliated cells in the sperm swim rapidly towards the
stationary egg-cell and seek to penetrate into it. As Hertwig showed in
1875, as a rule only one of the suitors is fortunate enough to reach
the desired goal. As soon as this favored spermatozoon has pierced
into the body of the ovum with its head (the nucleus of the cell), a
thin mucous layer is detached from the ovum which prevents the further
entrance of spermatozoa. The formation of this protective membrane
was only prevented when Hertwig kept the ovum stiff with cold by
lowering the temperature, or benumbed it with narcotics (chloroform,
morphia, nicotine, etc.); then there was "super-impregnation" or
"poly-spermy"--a number of sperm-threads pierced into the body of
the unconscious ovum. This remarkable fact proved that there is a
low degree of "cellular instinct" (or, at least, of specific, lively
sensation) in the sexual cells just as effectively as do the important
phenomena that immediately follow in their interior. Both nuclei--that
of the ovum and of the spermatozoon--attract each other, approach, and,
on contact, completely fuse together. Thus from the impregnated ovum
arises the important new cell which we call the "stem-cell" (_cytula_),
from the repeated segmentation of which the whole polycellular organism
is evolved.

The psychological information which is afforded by these remarkable
facts of impregnation, which have only been properly observed
during the last twenty-five years, is supremely important; its vast
significance has hitherto been very far from appreciated. We shall
condense the main conclusions of research in the following five theses:

I. Each human individual, like every other higher animal, is a single
simple cell at the commencement of his existence.

II. This "stem-cell" (cytula) is formed in the same manner in all
cases--that is, by the blending or copulation of two separate cells of
diverse origin, the female ovum and the male spermatozoon.

III. Each of these sexual cells has its own "cell-soul"--that is, each
is distinguished by a peculiar form of sensation and movement.

IV. At the moment of conception or impregnation, not only the
protoplasm and the nuclei of the two sexual cells coalesce, but also
their "cell-souls"; in other words, the potential energies which are
latent in both, and inseparable from the matter of the protoplasm,
unite for the formation of a new potential energy, the "germ-soul" of
the newly constructed stem-cell.

V. Consequently each personality owes his bodily and spiritual
qualities to both parents; by heredity the nucleus of the ovum
contributes a portion of the maternal features, while the nucleus of
the spermatozoon brings a part of the father's characteristics.

By these empirical facts of conception, moreover, the further fact of
extreme importance is established, that every man, like every other
animal, _has a beginning of existence_; the complete copulation of
the two sexual cell-nuclei marks the precise moment when not only the
body, but also the "soul," of the new stem-cell makes its appearance.
This fact suffices of itself to destroy the myth of the immortality
of the soul, to which we shall return later on. It suffices, too, for
the destruction of the still prevalent superstition that man owes
his personal existence to the favor of God. Its origin is rather to
be attributed solely to the "eros" of his parents, to that powerful
impulse that is common to all polycellular animals and plants,
and leads to their nuptial union. But the essential point in this
physiological process is not the "embrace," as was formerly supposed,
or the amorousness connected therewith; it is simply the introduction
of the spermatozoa into the vagina. This is the sole means, in the
land-dwelling animals, by which the fertilizing element can reach the
released ova (which usually takes place in the uterus in man). In the
case of the lower aquatic animals (fishes, mussels, medusæ, etc.) the
mature sexual elements on both sides are simply discharged into the
water, and their union is let to chance; they have no real copulation,
and so they show none of those higher psychic "erotic" functions which
play so conspicuous a part in the life of the higher animals. Hence
it is, also, that all the lower, non-copulating animals are wanting
in those interesting organs which Darwin has called "secondary sexual
characters," and which are the outcome of sexual selection: such are
the beard of man, the antlers of the stag, the beautiful plumage of
the bird of paradise and of so many other birds, together with other
distinctions of the male which are absent in the female.

Among the above theses as to the physiology of conception the
inheritance of the psychic qualities of the two parents is of
particular importance for psychological purposes. It is well known that
every child inherits from both his parents peculiarities of character,
temperament, talent, acuteness of sense, and strength of will. It
is equally well known that even psychic qualities are often (if not
always) transmitted from grandparents by heredity--often, in fact,
a man resembles his grandparents more than his parents in certain
respects; and that is true both of bodily and mental features. All
the chief laws of heredity which I first formulated in my _General
Morphology_, and popularized in my _Natural History of Creation_, are
just as valid and universal in their application to psychic phenomena
as to bodily structure--in fact, they are frequently more striking and
conspicuous in the former than in the latter.

However, the great province of heredity, to the inestimable importance
of which Darwin first opened our eyes in 1859, is thickly beset with
obscure problems and physiological difficulties. We dare not claim,
even after forty years of research, that all its aspects are clear
to us. Yet we have done so much that we can confidently speak of
heredity as a _physiological function_ of the organism, which is
directly connected with the faculty of generation; and we must reduce
it, like all other vital phenomena, to exclusively physical and
chemical processes, to the _mechanics of the protoplasm_. We now know
accurately enough the process of impregnation itself; we know that in
it the nucleus of the spermatozoon contributes the qualities of the
male parent, and the nucleus of the ovum gives the qualities of the
mother, to the newly born stem-cell. The blending of the two nuclei is
the "physiological moment" of heredity; by it the personal features of
both body and soul are transmitted to the new individual. These facts
of ontogeny are beyond the explanation of the dualistic and mystic
psychology which still prevails in the schools; whereas they find a
perfectly simple interpretation in our monistic philosophy.

The physiological fact which is most material for a correct appreciation
of individual psychogeny is the _continuity_ of the _psyche_ through
the rise and fall of generations. A new individual comes into
existence at the moment of conception; yet it is not an independent
entity, either in respect of its mental or its bodily features, but
merely the product of the blending of the two parental factors, the
maternal egg-cell and paternal sperm-cell. The cell-souls of these
two sexual cells combine in the act of conception for the formation
of a new cell-soul, just as truly as the two cell-nuclei, which are
the material vehicles of this psychic potential energy, unite to form
a new nucleus. As we now see that the individuals of one and the same
species--even sisters born of the same parents--always show certain
differences, however slight, we must assume that these variations
were already present in the chemical plasmatic constitution of the
generative cells themselves.[17]

These facts alone would suffice to explain the infinite variety of
individual features, of soul and of bodily form, that we find in the
organic world. As an extreme, but one-sided, consequence of them, there
is the theory of Weismann, which considers the _amphimixis_, or the
blending of the germ-plasm in sexual generation, to be the universal
and the sole cause of individual variability. This exclusive theory,
which is connected with his theory of the continuity of the germ-plasm,
is, in my opinion, an exaggeration. I am convinced, on the contrary,
that the great laws of _progressive heredity_ and of the correlative
_functional adaptation_ apply to the soul as well as to the body. The
new characteristics which the individual has acquired during life may
react to some extent on the molecular texture of the germ-plasm in
the egg-cell and sperm-cell, and may thus be transferred to the next
generation by heredity in certain conditions (naturally, only in the
form of latent energy).

Although in the soul-blending at the moment of conception only
the latent forces of the two parent souls are transmitted by the
coalescence of the erotic cell-nuclei, still it is possible that the
hereditary psychic influence of earlier, and sometimes very much
older, generations may be communicated at the same time. For the laws
of _latent heredity_ or atavism apply to the soul just as validly as
to the anatomical organization. We find these remarkable phenomena of
reversion in a very simple and instructive form in the alternation of
generations of the polyps and medusæ. Here we see two very different
generations alternate so regularly that the first resembles the third,
fifth, and so on; while the second (very different from the preceding)
is like the fourth, sixth, etc. (_Natural History of Creation_). We do
not find such alternation of generations in man and the higher animals
and plants, in which, owing to continuous heredity, each generation
resembles the next; nevertheless, even in these cases we often meet
with phenomena of reversion, which must be reduced to the same law of
latent heredity.

Eminent men often take more after their grandparents than their parents
even in the finer shades of psychic activity--in the possession of
certain artistic talents or inclinations, in force of character, and
in warmth of temperament; not infrequently there is a striking feature
which neither parents nor grandparents possessed, but which may be
traced a long way back to an older branch of the family. Even in
these remarkable cases of atavism the same laws of heredity apply to
the _psyche_ and to the physiognomy, to the personal quality of the
sense-organs, muscles, skeleton, and other parts of the body. We can
trace them most clearly in the reigning dynasties and in old families
of the nobility, whose conspicuous share in the life of the State has
given occasion to a more careful historical picture of the individuals
in the chain of generations--for instance, in the Hohenzollerns, the
princes of Orange, the Bourbons, etc., and in the Roman Cæsars.

The causal-nexus of _biontic_ (individual) and _phyletic_ (historical)
evolution, which I gave in my _General Morphology_ as the supreme law
at the root of all biogenetic research, has a universal application to
psychology no less than to morphology. I have fully treated the special
importance which it has with regard to man, in both respects, in the
first chapter of my _Anthropogeny_. In man, as in all other organisms,
"the embryonic development is an epitome of the historical development
of the species. This condensed and abbreviated recapitulation is the
more complete in proportion as the original _epitomized development_
(_palingenesis_) is preserved by a constant heredity; on the other
hand, it falls off from completeness in proportion as the later
_disturbing development_ (_cenogenesis_) is accentuated by varying

While we apply this law to the evolution of the soul, we must lay
special stress on the injunction to keep _both_ sides of it critically
before us. For, in the case of man, just as in all the higher animals
and plants, such appreciable perturbations of type (or _cenogeneses_)
have taken place during the millions of years of development that
the original simple idea of _palingenesis_, or "epitome of history,"
has been greatly disturbed and altered. While, on the one side, the
_palingenetic_ recapitulation is preserved by the laws of like-time
and like-place heredity, it is subject to an essential _cenogenetic_
change, on the other hand, by the laws of abbreviated and simplified
heredity. That is clearly seen in the embryonic evolution of the
psychic organs, the nervous system, the muscles, and the sense-organs.
But it applies in just the same manner to the psychic functions, which
are absolutely dependent on the normal construction of these organs.
Their evolution is subject to great cenogenetic modification in man
and all other viviparous animals, precisely because the complete
development of the embryo occupies a longer time within the body of
the mother. But we have to distinguish two periods of individual
psychogeny: (1) the embryonic, and (2) the post-embryonic development
of the soul.

I. _Embryonic Psychogeny._--The human foetus, or embryo, normally
takes nine months (or two hundred and seventy days) to develop in
the uterus. During this time it is entirely cut off from the outer
world, and protected, not only by the thick muscular wall of the womb,
but also by the special foetal membranes (_embryolemmata_) which
are common to all the three higher classes of vertebrates--reptiles,
birds, and mammals. In all the classes of amniotes these membranes
(the _amnion_ and the _serolemma_) develop in just the same fashion.
They represent the protective arrangements which were acquired by
the earliest reptiles (_proreptilia_), the common parents of all the
amniotes, in the Permian period (towards the end of the palæozoic
age), when these higher vertebrates accustomed themselves to live on
land and breathe the atmosphere. Their ancestors, the amphibia of the
Carboniferous period, still lived and breathed in the water, like their
earlier predecessors, the fishes.

In the case of these older and lower vertebrates that lived in the
water, the embryonic development had the palingenetic character in
a still higher degree, as is the case in most of the fishes and
amphibia of the present day. The familiar tadpole and the larva of
the salamander or the frog still preserve the structure of their
fish-ancestors in the first part of their life in the water; they
resemble them, likewise, in their habits of life, in breathing by
gills, in the action of their sense-organs, and in other psychic
organs. Then, when the interesting metamorphosis of the swimming
tadpole takes place, and when it adapts itself to a land-life, the
fish-like body changes into that of a four-footed, crawling amphibium;
instead of the gill-breathing in the water comes an exclusive
breathing of the atmosphere by means of lungs, and, with the changed
habits of life, even the psychic apparatus, the nervous system, and
the sense-organs reach a higher degree of construction. If we could
completely follow the psychogeny of the tadpole from beginning to end,
we should be able to apply the biogenetic law in many ways to its
psychic evolution. For it develops in direct communication with the
changing conditions of the outer world, and so must quickly adapt its
sensation and movement to these. The swimming tadpole has not only the
structure but the habits of life of a fish, and only acquires those of
a frog in its metamorphosis.

It is different with man and all the other amniotes; their embryo is
entirely withdrawn from the direct influence of the outer world, and
cut off from any reciprocal action therewith, by enclosure in its
protective membranes. Besides, the special care of the young on the
part of the amniotes gives their embryo much more favorable conditions
for the cenogenetic abbreviation of the palingenetic evolution. There
is, in the first place, the excellent arrangement for the nourishment
of the embryo; in the reptiles, birds, and monotremes (the oviparous
mammals) it is effected by the great yellow nutritive yelk, which is
associated with the egg; in the rest of the mammals (the marsupials and
placentals) it is effected by the mother's blood, which is conducted to
the foetus by the blood-vessels of the yelk-sac and the allantois.
In the case of the most highly developed placentals this elaborate
nutritive arrangement has reached the highest degree of perfection by
the construction of a placenta; hence in these classes the embryo is
fully developed before birth. But its soul remains during all this time
in a state of embryonic slumber, a state of repose which Preyer has
justly compared to the hibernation of animals. We have a similar long
sleep in the chrysalis stage of those insects which undergo a complete
metamorphosis--butterflies, bees, flies, beetles, and so forth. This
sleep of the pupa, during which the most important formations of
organs and tissues take place, is the more interesting from the fact
that the preceding condition of the free larva (caterpillar, grub, or
maggot) included a highly developed psychic activity, and that this is,
significantly, lower than the stage which is seen afterwards (when the
chrysalis sleep is over) in the perfect, winged, sexually mature insect.

Man's psychic activity, like that of most of the higher animals, runs
through a long series of stages of development during the individual
life. We may single out the five following as the most important of

I. The soul of the new-born infant up to the birth of self-consciousness
and the learning of speech.

II. The soul of the boy or girl up to puberty (_i.e._, until the
awakening of the sexual instinct).

III. The soul of the youth or maiden up to the time of sexual
intercourse (the "idealist" period).

IV. The soul of the grown man and the mature woman (the period of
full maturity and of the founding of families, lasting until about
the sixtieth year for the man and the fiftieth for the woman--until
_involution_ sets in).

V. The soul of the old man or woman (the period of degeneration).

Man's psychic life runs the same evolution--upward progress, full
maturity, and downward degeneration--as every other vital activity in
his organization.



    Gradual Historical Evolution of the Human Soul from the Animal
    Soul--Methods of Phylogenetic Psychology--Four Chief Stages in
    the Phylogeny of the Soul: I. The Cell-Soul (Cytopsyche) of the
    Protist (Infusoria, Ova, etc.): Cellular Psychology; II. The Soul
    of a Colony of Cells, or the Cenobitic Soul (Coenopsyche):
    Psychology of the Morula and Blastula; III. The Soul of the Tissue
    (Histopsyche): Its Twofold Nature: The Soul of the Plant: The Soul
    of the Lower, Nerveless Animal: Double Soul of the Siphonophora
    (Personal and Kormal Soul); IV. The Nerve-Soul (Neuropsyche)
    of the Higher Animal--Three Sections of its Psychic Apparatus:
    Sense-Organs, Muscles, and Nerves--Typical Formation of the
    Nerve-Centre in the Various Groups of Animals--Psychic Organ of the
    Vertebrate: the Brain and the Spinal Cord--Phylogeny of the Mammal

The theory of descent, combined with anthropological research, has
convinced us of the descent of our human organism from a long series
of animal ancestors by a slow and gradual transformation occupying
many millions of years. Since, then, we cannot dissever man's psychic
life from the rest of his vital functions--we are rather forced to a
conviction of the natural evolution of our whole body and mind--it
becomes one of the main tasks of the modern monistic psychology to
trace the stages of the historical development of the soul of man from
the soul of the brute. Our "phylogeny of the soul" seeks to attain this
object; it may also, as a branch of general psychology, be called
_phylogenetic_ psychology, or, in contradistinction to _biontic_
(individual), _phyletic psychogeny_. And, although this new science has
scarcely been taken up in earnest yet, and most of the "professional"
psychologists deny its very right to existence, we must claim for it
the utmost importance and the deepest interest. For, in our opinion, it
is its special province to solve for us the great enigma of the nature
and origin of the human soul.

The methods and paths which will lead us to the remote goal of a
complete phylogenetic psychology--a goal that is still buried in the
mists of the future, and almost imperceptible to many--do not differ
from those of other branches of evolutionary research. Comparative
anatomy, physiology, and ontogeny are of the first importance. Much
support is given also by palæontology, for the order in which the
fossil remains of the various classes of vertebrates succeed each other
in the course of organic evolution reveals to us, to some extent,
the gradual growth of their psychic power as well as their phyletic
connection. We must admit that we are here, as we are in every branch
of phylogenetic research, driven to the construction of a number of
hypotheses in order to fill up the considerable lacunæ of empirical
phylogeny. Yet these hypotheses cast so clear and significant a light
on the chief stages of historical development that we are afforded a
most gratifying insight into their entire course.

The comparative psychology of man and the higher animals enables us
to learn from the highest group of the placentals, the primates, the
long strides by which the human soul has advanced beyond the _psyche_
of the anthropoid ape. The phylogeny of the mammals and of the lower
vertebrates acquaints us with the long series of the earlier ancestors
of the primates which have arisen within this stem since the Silurian
age. All these vertebrates agree in the structure and development of
their characteristic psychic organ--the spinal cord. We learn from
the comparative anatomy of the vermalia that this spinal cord has
been evolved from a dorsal _acroganglion_, or vertical brain, of an
invertebrate ancestor. We learn, further, from comparative ontogeny
that this simple psychic organ has been evolved from the stratum of
cells in the outer germinal layer, the ectoderm, of the platodes. In
these earliest flat-worms, which have no specialized nervous system,
the outer skin-covering serves as a general sensitive and psychic
organ. Finally, comparative embryology teaches us that these simple
metazoa have arisen by gastrulation from blastæades, from hollow
spheres, the wall of which is merely one simple layer of cells, the
_blastoderm_; and the same science, with the aid of the biogenetic law,
explains how these protozoic coenobia originally sprang from the
simplest unicellular organisms.

On a critical study of these different embryonic formations, the
evolution of which from each other we can directly observe under the
microscope, we arrive, by means of the great law of biogeny, at a
series of most important conclusions as to the chief stages in the
development of our psychic life. We may distinguish eight of these to
begin with:

I. Unicellular protozoa with a simple cell-soul: the infusoria.

II. Multicellular protozoa with a communal soul: the catallacta.

III. The earliest metazoa with an epithelial soul: the platodes.

IV. Invertebrate ancestors with a simple vertical brain: the vermalia.

V. Vertebrates without skull or brain, with a simple spinal cord: the

VI. Animals with skull and brain (of five vesicles): the craniota.

VII. Mammals with predominant development of the cortex of the brain:
the placentals.

VIII. The higher anthropoid apes and man, with organs of thought (in
the cerebrum): the anthropomorpha.

Among these eight stages in the development of the human soul we may
further distinguish more or less clearly a number of subordinate
stages. Naturally, however, in reconstructing them we have to fall
back on the same defective evidence of empirical psychology which the
comparative anatomy and physiology of the actual fauna affords us. As
the craniote animals of the sixth stage--and these are true fishes--are
already found fossilized in the Silurian system, we are forced to
assume that the five preceding series of ancestors (which were
incapable of fossilization) were evolved in an earlier, pre-Silurian

I. _The cell-soul_ (_or cytopsyche_): first stage of phyletic
psychogenesis.--The earliest ancestors of man and all other animals
were unicellular protozoa. This fundamental hypothesis of rational
phylogeny is based, in virtue of the phylogenetic law, on the
familiar embryological fact that every man, like every other metazoon
(_i.e._, every multicellular organism with tissues), begins his
personal existence as a simple cell, the stem-cell (_cytula_), or the
impregnated egg-cell (see p. 63). As this cell has a "soul" from the
commencement, so had also the corresponding unicellular _ancestral
forms_, which were represented in the oldest series of man's ancestors
by a number of different protozoa.

We learn the character of the psychic activity of these unicellular
organisms from the comparative physiology of the protists of to-day.
Close observation and careful experiment have opened out to us in this
respect, in the second half of the nineteenth century, a new world of
the most interesting phenomena. The best description of them was given
by Max Verworn in his thoughtful work, based on original research,
_Psycho-physiological Studies of the Protists_. The work includes also
the few earlier observations of the "psychic life of the protist."
Verworn came to the firm conclusion that the psychic processes are
unconscious in all the protists, that the phenomena of sensation
and movement coincide with the molecular vital processes in their
protoplasm, and that their ultimate causes are to be sought in the
properties of the protoplasmic molecules (the _plastidules_). "Hence
the psychic phenomena of the protists form a bridge that connects the
chemical processes of the inorganic world with the psychic life of
the highest animals; they represent the germ of the highest psychic
phenomena of the metazoa and of man."

The careful observations and many experiments of Verworn, together
with those of Wilhelm Engelmann, Wilhelm Preyer, Richard Hertwig, and
other more recent students of the protists, afford conclusive evidence
for my "theory of the cell-soul" (1866). On the strength of several
years of study of different kinds of protists, especially rhizopods and
infusoria, I published a theory thirty-three years ago to the effect
that every living cell has psychic properties, and that the psychic
life of the multicellular animals and plants is merely the sum total of
the psychic functions of the cells which build up their structure. In
the lower groups (in algæ and sponges, for instance) _all_ the cells of
the body have an equal share in it (or with very slight differences);
in the higher groups, in harmony with the law of the "division of
labor," only a select portion of them are involved--the "soul-cells."
The important consequences of this "cellular psychology" were partly
treated in my work on _The Perigenesis of the Plastidule_ (1876),
and partly in my speech at Munich, in 1877, on "Modern Evolution in
Relation to the Whole of Science." A more popular presentation of
them is to be found in my two Vienna papers (1878) on "The Origin and
Development of the Sense-Organs" and on "Cell-Souls and Soul-Cells."

Moreover, the cell-soul, even within the limits of the protist world,
presents a long series of stages of development, from the most simple
and primitive to a comparatively elaborate activity. In the earliest
and simplest protists the faculty of sensation and movement is equally
distributed over the entire protoplasm of the homogeneous morsel; in
the higher forms certain "cell-instruments," or _organella_, appear,
as their physiological organs. Motor cell-parts of that character are
found in the pseudopodia of the rhizopods, and the vibrating hairs,
lashes, or cilia of the infusoria. The cell-nucleus, which is wanting
in the earlier and lower protists, is considered to be an internal
central organ of the cell-life. It is especially noteworthy, from a
physiologico-chemical point of view, that the very earliest protists
were plasmodomous, with plant-like nutrition--hence _protophyta_, or
primitive plants; from these came as a secondary stage, by metasitism,
the first plasmophagi, with animal nutrition--the _protozoa_, or
primitive animals.[18] This metasitism, or circulation of nutritive
matter, implies an important psychological advance; with it began the
development of those characteristic properties of the animal soul which
are wanting in the plant.

We find the highest development of the animal cell-soul in the class
of ciliata, or ciliated infusoria. When we compare their activity
with the corresponding psychic life of the higher, multicellular
animals, we find scarcely any psychological difference; the sensitive
and motor _organella_ of these protozoa seem to accomplish the same
as the sense-organs, nerves, and muscles of the metazoa. Indeed, we
have found in the great cell-nucleus (_meganucleus_) of the infusoria
a central organ of psychic activity, which plays much the same part
in their unicellular organism as the brain does in the psychic life
of higher animals. However, it is very difficult to determine how far
this comparison is justified; the views of experts diverge considerably
over the matter. Some take all spontaneous bodily movement in them to
be automatic, or impulsive, and all stimulated movement to be reflex;
others are convinced that such movements are partly voluntary and
intentional. The latter would attribute to the infusoria a certain
degree of consciousness, and even self-consciousness; but this is
rejected by the others. However that very difficult question may be
settled, it does not alter the fact that these unicellular protozoa
give proof of the possession of a highly developed "cell-soul," which
is of great interest for a correct decision as to the _psyche_ of our
earliest unicellular ancestors.

II. _The communal or cenobitic soul_ (_coenopsyche_): second stage of
phyletic psychogenesis.--Individual development begins, in man and in
all other multicellular animals, with the repeated segmentation of one
simple cell. This _stem-cell_, the impregnated ovum, divides first into
two daughter cells, by a process of ordinary indirect segmentation;
as the process is repeated there arise (by equal division of the egg)
successively four, eight, sixteen, thirty-two, sixty-four such new
cells, or "blastomeres." Usually (that is, in the case of the majority
of animals) an irregular enlargement sooner or later takes the place
of this original regular division of cells. But the result is the same
in all cases--the formation of a (generally spherical) cluster of
heterogeneous (originally homogeneous) cells. This stage is called the
_morula_ ("mulberry," which it somewhat resembles in shape). Then, as
a rule, a fluid gathers in the interior of this aggregate of cells; it
changes into a spherical vesicle; all the cells go to its surface, and
arrange themselves in one simple layer--the _blastoderm_. The hollow
sphere which is thus formed is the important stage of the "germinal
vesicle," the _blastula_, or blastosphere.

The psychological phenomena which we directly observe in the formation
of the blastula are partly sensations, partly movements, of this
community of cells. The movements may be divided into two groups: (1)
the inner movements, which are always repeated in substantially the
same manner in the process of ordinary (indirect) segmentation of
cells (formation of the axis of the nucleus, mitosis, karyokinesis,
etc.); (2) the outer movements, which are seen in the regular change of
position of the social cells and their grouping for the construction
of the blastoderm. We assume that these movements are hereditary and
unconscious, because they are always determined in the same fashion by
heredity from the earlier protist ancestors. The sensations also fall
into two groups: (1) the sensations of the individual cells, which
reveal themselves in the assertion of their individual independence and
their relation to neighboring cells (with which they are in contact,
and partly in direct combination, by means of protoplasmic fibres); (2)
the common sensation of the entire community of cells, which is seen in
the individual formation of the _blastula_ as a hollow vesicle.

The causal interpretation of the formation of the blastula is given us
by the biogenetic law, which explains the phenomena we directly observe
to be the outcome of heredity, and relates them to corresponding
historical processes which took place long ago in the origin of the
earliest protist-coenobia, the blastæads. But we get a physiological
and psychological insight into these important phenomena of the
earliest cell-communities by observation and experiment on their modern
representatives. Such permanent cell-communities or colonies are still
found in great numbers both among the plasmodomous primitive plants
(for instance, the paulotomacea, diatomacea, volvocinæ, etc.) and the
plasmophagous primitive animals (the infusoria and rhizopods). In
all these coenobia we can easily distinguish two different grades
of psychic activity: (1) the cell-soul of the individual cells (the
"elementary organisms") and (2) the communal soul of the entire colony.

III. _The tissue-soul_ (_histopsyche_): third stage of phyletic
psychogenesis.--In all multicellular, tissue-forming plants
(_metaphyta_) and in the lowest, nerveless classes of tissue-forming
animals (_metazoa_) we have to distinguish two different forms of
psychic activity--namely: (1) the _psyche_ of the individual cells
which compose the tissue, and (2) the _psyche_ of the tissue itself, or
of the "cell-state" which is made up of the tissues. This "tissue-soul"
is the higher psychological function which gives physiological
individuality to the compound multicellular organism as a true
"cell-commonwealth." It controls all the separate "cell-souls" of the
social cells--the mutually dependent "citizens" which constitute the
community. This fundamental twofold character of the _psyche_ in the
metaphyta and the lower, nerveless metazoa is very important. It may
be verified by unprejudiced observation and suitable experiment. In
the first place, each single cell has its own sensation and movement,
and, in addition, each tissue and each organ, composed of a number
of homogeneous cells, has its special irritability and psychic unity
(_e.g._, the pollen and stamens).

A. _The plant-soul_ (_phytopsyche_) is, in our view, the summary of
the entire psychic activity of the tissue-forming, multicellular plant
(the _metaphyton_, as distinct from the unicellular _protophyton_);
it is, however, the subject of the most diverse opinions even at the
present day. It was once customary to draw an essential distinction
between the plant and the animal, on the ground that the latter had
a "soul" and the plant had none. However, an unprejudiced comparison
of the irritability and movements of various higher plants and lower
animals convinced many observers, even at the beginning of the century,
that there must be a "soul" on both sides. At a later date Fechner,
Leitgeb, and others strongly contended for the plant-soul. But a
profounder knowledge of the subject was obtained when the similarity
of the elementary structure of the plant and of the animal was proved
by the cellular theory, and especially when the similarity of conduct
of the active, living protoplasm in both was shown in the plasma
theory of Max Schultze (1859). Modern comparative physiology has
shown that the physiological attitude towards various stimuli (light,
heat, electricity, gravity, friction, chemical action, etc.) of the
"sensitive" portions of many plants and animals is exactly the same,
and that the reflex movements which the stimuli elicit take place in
precisely the same manner on both sides. Hence, if it was necessary to
attribute this activity to a "soul" in the lower, nerveless metazoa
(sponges, polyps, etc.), it was also necessary in the case of many
(if not all) metaphyta, at least in the very sensitive _mimosa_, the
"fly-traps" (_dionaea_ and _drosera_), and the numerous kinds of
climbing plants.

It is true that modern vegetal physiology has given a purely physical
explanation of many of these stimulated movements, or tropisms, by
special features of growth, variations of pressure, etc. Yet these
mechanical causes are neither more nor less _psychophysical_ than
the similar "reflex movements" of the sponges, polyps, and other
nerveless metazoa, even though their mechanism is entirely different.
The character of the tissue-soul reveals itself in the same way in
both cases--the cells of the tissue (the regular, orderly structure
of cells) transmit the stimuli they have received in one part, and
thus provoke movements of other parts, or of the whole organ. This
transmission of stimuli has as much title to be called "psychic
activity" as its more complete form in the higher animals with nerves;
the anatomic explanation of it is that the social cells of the tissue,
or cell-community, are not isolated from each other (as was formerly
supposed), but are connected throughout by fine threads or bridges of
protoplasm. When the sensitive mimosa closes its graceful leaves and
droops its stalk at contact, or on being shaken; when the irritable
fly-trap (the dionæa) swiftly clasps its leaves together at a touch,
and captures a fly; the sensation seems to be keener, the transmission
of the stimulus more rapid, and the movement more energetic than in the
reflex action of the stimulated bath-sponge and many other sponges.

B. _The soul of the nerveless metazoa._--Of very special interest for
comparative psychology in general, and for the phylogeny of the animal
soul in particular, is the psychic activity of those lower metazoa
which have tissues, and sometimes differentiated organs, but no nerves
or specific organs of sense. To this category belong four different
groups of the earliest coelenterates: (_a_) the gastræads, (_b_) the
platodaria, (_c_) the sponges, and (_d_) the hydropolyps, the lowest
form of cnidaria.

The _gastraeads_ (or animals with a primitive gut) form a small group
of the lowest coelenterates, which is of great importance as the
common ancestral group of all the metazoa. The body of these little
swimming animals looks like a tiny (generally oval) vesicle, which has
a simple cavity with one opening--the primitive gut and the primitive
mouth. The wall of the digestive cavity is formed of two simple
layers of cells, or epithelium, the inner of which--the gut-layer--is
responsible for the vegetal activity of nourishment, while the outer,
or skin-layer, discharges the animal functions of movement and
sensation. The homogeneous sensitive cells of the skin-layer bear long,
slender hairs or lashes (_cilia_), by the vibration of which the
swimming motion is effected. The few surviving forms of gastræads,
the gastræmaria (_trichoplacidae_) and cyemaria (_orthonectidae_),
are extremely interesting, from the fact that they remain throughout
life at a stage of structure which is passed by all the other metazoa
(from the sponge to man) at the commencement of their embryonic
development. As I have shown in my _Theory of the Gastraea_ (1872),
a very characteristic embryonic form, the _gastrula_, is immediately
developed from the _blastula_ in all the tissue animals. The germinal
membrane (blastoderm), which represents the wall of the hollow vesicle,
forms a depression at one side, and this soon sinks in so deep that the
inner cavity of the vesicle disappears. The half of the membrane which
bends in is thus laid on, and inside, the other half; the latter forms
the _skin-layer_, or outer germinal layer (ectoderm or epiblast), and
the former becomes the _gut-layer_, or inner germinal layer (endoderm
or hypoblast). The new cavity of the cup-shaped body is the digestive
stomach cavity (the _progaste_), and its opening is the primitive mouth
(or _prostoma_).[19] The skin-layer, or ectoderm, is the primitive
psychic organ in the metazoa; from it, in all the nerve animals, not
only the external skin and the organs of sense, but also the nervous
system, are developed. In the gastræads, which have no nerves, all the
cells which compose the simple epithelium of the ectoderm are equally
organs of sensation and of movement; we have here the tissue-soul in
its simplest form.

The platodaria, the earliest and simplest form of the platodes, seem to
be of the same primitive construction. Some of these cryptocoela--the
_convoluta_, etc.--have no specific nervous system, while their
nearest relatives, the turbellaria, have already differentiated one,
and even developed a vertical brain.

The _sponges_ form a peculiar group in the animal world, which differs
widely in organization from all the other metazoa. The innumerable
kinds of sponges grow, as a rule, at the bottom of the sea. The
simplest form of sponge, the _olynthus_, is in reality nothing more
than a _gastraea_, the body-wall of which is perforated like a sieve,
with fine pores, in order to permit the entrance of the nourishing
stream of water. In the majority of sponges--even in the most familiar
one, the bath-sponge--the bulbous organism constructs a kind of stem or
tree, which is made up of thousands of these gastræads, and permeated
by a nutritive system of canals. Sensation and movement are only
developed in the faintest degree in the sponges; they have no nerves,
muscles, or organs of sense. It was therefore quite natural that such
stationary, shapeless, insensitive animals should have been commonly
taken to be plants in earlier years. Their psychic life--for which no
special organs have been differentiated--is far inferior to that of the
mimosa and other sensitive plants.

_The soul of the cnidaria_ is of the utmost importance in comparative
and phylogenetic psychology; for in this numerous group of the
coelenterates the historical evolution of the _nerve-soul_ out of the
_tissue-soul_ is repeated before our eyes. To this group belong the
innumerable classes of stationary polyps and corals, and of swimming
medusæ and siphonophora. As the common ancestor of all the cnidaria
we can safely assign a very simple polyp, which is substantially
the same in structure as the common, still surviving, fresh-water
polyp--the hydra. Yet the hydræ, and the stationary, closely related
_hydropolyps_, have no nerves or higher sense-organs, although they
are extremely sensitive. On the other hand, the free-swimming medusæ,
which are developed from them--and are still connected with them
by alternation of generations--have an independent nervous system
and specific sense-organs. Here, also, we may directly observe the
ontogenetic evolution of the nerve-soul (_neuropsyche_) out of the
tissue-soul (_histopsyche_), and thus learn its phylogenetic origin.
This is the more interesting as such phenomena are _polyphyletic_--that
is, they have occurred several times--more than once, at least--quite
independently. As I have shown elsewhere, the hydromedusæ have arisen
from the hydropolyps in a different manner from that of the evolution
of the scyphomedusæ from the scyphopolyps; the gemmation is terminal in
the case of the latter, and lateral with the former. In addition, both
groups have characteristic hereditary differences in the more minute
structure of their psychic organs. The class of siphonophora is also
very interesting to the psychologist. In these pretty, free-swimming
organisms, which come from the hydromedusæ we can observe a double
soul: the _personal soul_ of the numerous individualities which compose
them, and the common, harmoniously acting psyche of the entire colony.

IV. _The nerve-soul_ (_neuropsyche_): fourth stage of phyletic
psychogeny.--The psychic life of all the higher animals is conducted,
as in man, by means of a more or less complicated "psychic apparatus."
This apparatus is always composed of three chief sections: the _organs
of sense_ are responsible for the various sensations; the _muscles_
effect the movements; the _nerves_ form the connection between the
two by means of a special central organ, the brain or ganglion. The
arrangement and action of this psychic mechanism have been frequently
compared with those of a telegraphic system: the nerves are the wires,
the brain the central, and the sense-organs subordinate stations. The
motor nerves conduct the commands of the will centrifugally from the
nerve-centre to the muscles, by the contraction of which they produce
the movements: the sensitive nerves transmit the various sensations
centripetally--that is, from the peripheral sense-organs to the
brain, and thus render an account of the impressions they receive
from the outer world. The ganglionic cells, or "psychic cells," which
compose the central nervous organ, are the most perfect of all organic
elements; they not only conduct the commerce between the muscles and
the organs of sense, but they also effect the highest performances of
the animal soul, the formation of ideas and thoughts, and especially

The great progress of anatomy, physiology, histology, and ontogeny has
recently added a wealth of interesting discoveries to our knowledge of
the mechanism of the soul. If speculative philosophy assimilated only
the most important of these significant results of empirical biology,
it would have a very different character from that it unfortunately
presents. As I have not space for an exhaustive treatment of them here,
I will confine myself to a relation of the chief facts.

Each of the higher animal species has a characteristic psychic organ;
the central nervous system of each has certain peculiarities of shape,
position, and composition. The medusæ, among the radiating cnidaria,
have a ring of nervous matter at the border of the fringe, generally
provided with four or eight ganglia. The mouth of the five-rayed
cnidarion is girt with a nerve-ring, from which proceed five branches.
The bi-symmetrical _platodes_ and the _vermalia_ have a vertical
brain, or acroganglion, composed of two dorsal ganglia, lying above
the mouth; from these "upper ganglia" two branch nerves proceed to the
skin and the muscles. In some of the vermalia and in the mollusca a
pair of ventral "lower ganglia" are added, which are connected with
the former by a ring round the gullet. This ring is found also in the
_articulata_; but in these it is continued on the belly side of the
long body as a ventral medulla, a double fibre like a rope-ladder,
which expands into a double ganglion in each member. The vertebrates
have an entirely different formation of the psychic organ; they have
always a spinal medulla developed at the back of the body; and from an
expansion of its fore part there arises subsequently the characteristic
vesicular brain.[20]

Although the psychic organs of the higher species of animals differ
very materially in position, form, and composition, nevertheless
comparative anatomy is in a position to prove a common origin for most
of them--namely, from the vertical brain of the platodes and vermalia;
they have all, moreover, had their origin in the outermost layer of the
embryo, the _ectoderm_, or outer skin-layer. Hence we find the same
typical structure in all varieties of the central nervous organ--a
combination of ganglionic cells, or "psychic cells" (the real active
elementary organs of the soul), and of nerve-fibres, which effect the
connection and transmission of the action.

The first fact we meet in the comparative psychology of the vertebrates,
and which should be the empirical starting-point of all scientific
human psychology, is the characteristic structure of the central
nervous system. This central psychic organ has a particular position,
shape, and texture in the vertebrate as it has in all the higher
species. In every case we find a spinal medulla, a strong cylindrical
nervous cord, which runs down the middle of the back, in the upper
part of the vertebral column (or the cord which represents it). In
every case a number of nerves branch off from this medulla in regular
division, one pair to each segment or vertebra. In every case this
medullary cord arises in the same way in the foetus; a fine groove
appears in the middle axis of the skin at the back; then the parallel
borders of this medullary groove are lifted up a little, bend over
towards each other, and form into a kind of tube.

The long dorsal cylindrical medullary tube which is thus formed is
thoroughly characteristic of the vertebrates; it is always the same in
the early embryonic sketch of the organism, and it is always the chief
feature of the different kinds of psychic organ which evolve from it in
time. Only one single group of invertebrates has a similar structure:
the rare, marine _tunicata_, copelata, ascidia, and thalidiæ. These
animals have other important peculiarities of structure (especially
in the chorda and the gut) which show a striking divergence from
the other invertebrates and resemblance to the vertebrates. The
inference we draw is that both these groups, the vertebrates and the
tunicates, have arisen from a common ancestral group of the vermalia,
the _prochordonia_.[21] Still, there is a great difference between
the two classes in the fact that the body of the tunicate does not
articulate, or form members, and has a very simple organization (most
of them subsequently attach themselves to the bottom of the sea and
degenerate). The vertebrate, on the other hand, is characterized
by an early development of internal members, and the formation of
pro-vertebræ (_vertebratio_). This prepares the way for the much higher
development of their organism, which finally attains perfection in man.
This is easily seen in the finer structure of his spinal cord, and in
the development of a number of segmental pairs of nerves, the spinal
nerves, which proceed to the various parts of the body.

The long ancestral history of our "vertebrate soul" commences with the
formation of the most rudimentary spinal cord in the earliest acrania;
slowly and gradually, through a period of many millions of years, it
conducts to that marvellous structure of the human brain which seems
to entitle the highest primate form to quite an exceptional position
in nature. Since a clear conception of this slow and steady progress
of our phyletic psychogeny is indispensable for a true psychology, we
must divide that vast period into a number of stages or sections: in
each of them the perfecting of the structure of the nervous centre has
been accompanied by a corresponding evolution of its function, the
_psyche_. I distinguish eight of these periods in the phylogeny of
the spinal cord, which are characterized by eight different groups of
vertebrates: (1) the acrania; (2) the cyclostomata; (3) the fishes; (4)
the amphibia; (5) the implacental mammals (monotremes and marsupials);
(6) the earlier placental mammals, especially the prosimiæ; (7) the
younger primates, the simiæ; and (8) the anthropoid apes and man.

I. First stage--the _acrania_: their only modern representative is the
lancelot or amphioxus; the psychic organ remains a simple medullary
tube, and contains a regularly segmented spinal cord, without brain.

II. Second stage--the _cyclostomata_: the oldest group of the craniota,
now only represented by the _petromyzontes_ and _myxinoides_:
the fore-termination of the cord expands into a vesicle, which
then subdivides into five successive parts--the great-brain,
intermediate-brain, middle-brain, little-brain, and hind-brain: these
five cerebral vesicles form the common type from which the brain of all
craniota has evolved, from the lamprey to man.

III. Third stage--the _primitive fishes_ (_selachii_): similar to the
modern shark: in these oldest fishes, from which all the gnathostomata
descend, the more pronounced division of the five cerebral vesicles
sets in.

IV. Fourth stage--the _amphibia_. These earliest land animals, making
their first appearance in the Carboniferous period, represent the
commencement of the characteristic structure of the _tetrapod_ and
a corresponding development of the fish-brain: it advances still
further in their Permian successors, the _reptiles_, the earliest
representatives of which, the _tocosauria_, are the common ancestors of
all the amniota (reptiles and birds on one side, mammals on the other).

V.-VIII. Fifth to the eighth stages--the _mammals_. I have exhaustively
treated, and illustrated with a number of plates, in my _Anthropogeny_,
the evolution of our nervous system and the correlative question of the
development of the soul. I have now, therefore, merely to refer the
reader to that work. It only remains for me to add a few remarks on the
last and most interesting class of facts pertaining to this--to the
evolution of the soul and its organs within the limits of the class
mammalia. In doing so, I must remind the reader that the _monophyletic
origin_ of this class--that is, the descent of all the mammals from
one common ancestral form (of the Triassic period)--is now fully

The most important consequence of the monophyletic origin of the
mammals is the necessity of deriving the human soul from a long
evolutionary series of other mammal souls. A deep anatomical and
physiological gulf separated the brain structure and the dependent
psychic activity of the higher mammals from those of the lower:
this gulf, however, is completely bridged over by a long series of
intermediate stages. The period of at least fourteen (more than a
hundred, on other estimates) million years, which has elapsed since the
commencement of the Triassic period, is amply sufficient to allow even
the greatest psychological advance. The following is a summary of the
results of investigation in this quarter, which has recently been very

I. The brain of the mammal is differentiated from that of the other
vertebrates by certain features, which are found in all branches of the
class; especially by a preponderant development of the first and fourth
vesicles, the cerebrum and cerebellum, while the third vesicle, the
middle brain, disappears altogether.

II. The brain development of the lowest and earliest mammals (the
monotremes, marsupials, and prochoriates) is closely allied to
that of their palæozoic ancestors, the Carboniferous amphibia (the
_stegocephala_) and the Permian reptiles (the _tocosauria_).

III. During the Tertiary period commences the typical development of
the cerebrum, which distinguishes the younger mammals so strikingly
from the older.

IV. The special development (quantitatively and qualitatively) of
the cerebrum which is so prominent a feature in man, and which is the
root of his pre-eminent psychic achievements, is only found, outside
humanity, in a small section of the most highly developed mammals of
the earlier Tertiary epoch, especially in the anthropoid apes.

V. The differences of brain structure and psychic faculty which
separate man from the anthropoid ape are slighter than the corresponding
interval between the anthropoid apes and the lower primates (the
earliest simiæ and prosimiæ).

VI. Consequently, the historical, gradual evolution of the human soul
from a long chain of higher and lower mammal souls must, by application
of the universally valid phyletic laws of the theory of descent, be
regarded as a _fact_ which has been scientifically proved.



    Consciousness as a Natural Phenomenon--Its Definition--Difficulties
    of the Problem--Its Relation to the Life of the Soul--Our
    Human Consciousness--Various Theories: I. Anthropistic
    Theory (Descartes); II. Neurological Theory (Darwin);
    III. Animal Theory (Schopenhauer); IV. Biological Theory
    (Fechner); V. Cellular Theory (Fritz Schultze); VI. Atomistic
    Theory--Monistic and Dualistic Theories--Transcendental
    Character of Consciousness--The Ignorabimus Verdict of Du
    Bois-Reymond--Physiology of Consciousness--Discovery of the
    Organs of Thought by Flechsig--Pathology--Double and Intermittent
    Consciousness--Ontogeny of Consciousness: Modifications at
    Different Ages--Phylogeny of Consciousness--Formation of Concepts

No phenomenon of the life of the soul is so wonderful and so variously
interpreted as consciousness. The most contradictory views are current
to-day, as they were two thousand years ago, not only with regard to
the nature of this psychic function and its relation to the body,
but even as to its diffusion in the organic world and its origin and
development. It is more responsible than any other psychic faculty for
the erroneous idea of an "immaterial soul" and the belief in "personal
immortality"; many of the gravest errors that still dominate even
our modern civilization may be traced to it. Hence it is that I have
entitled consciousness "the central mystery of psychology"; it is
the strong citadel of all mystic and dualistic errors, before whose
ramparts the best-equipped efforts of reason threaten to miscarry. This
fact would suffice of itself to induce us to make a special critical
study of consciousness from our monistic point of view. We shall see
that consciousness is simply a natural phenomenon like any other
psychic quality, and that it is subject to the law of substance like
all other natural phenomena.

Even as to the elementary idea of consciousness, its contents and
extension, the views of the most distinguished philosophers and
scientists are widely divergent. Perhaps the meaning of consciousness
is best conceived as an _internal perception_, and compared with the
action of _a mirror_. As its two chief departments we distinguish
objective and subjective consciousness--consciousness of the world,
the non-ego, and of the ego. By far the greater part of our conscious
activity, as Schopenhauer justly remarked, belongs to the consciousness
of the outer world, or the non-ego: this _world-consciousness_
embraces all possible phenomena of the outer world which are in any
sense accessible to our minds. Much more contracted is the sphere
of _self-consciousness_, the internal mirror of all our own psychic
activity, all our presentations, sensations, and volitions.

Many distinguished thinkers, especially on the physiological side
(Wundt and Ziehen, for instance) take the ideas of consciousness and
psychic function to be identical--"all psychic action is conscious";
the province of psychic life, they say, is coextensive with that
of consciousness. In our opinion, such a definition gives an undue
extension to the meaning of consciousness, and occasions many
errors and misunderstandings. We share, rather, the view of other
philosophers (Romanes, Fritz Schultze, and Paulsen), that even our
unconscious presentations, sensations, and volitions pertain to our
psychic life; indeed, the province of these unconscious psychic actions
(reflex action, and so forth) is far more extensive than that of
consciousness. Moreover, the two provinces are intimately connected,
and are separated by no sharp line of demarcation. An unconscious
presentation may become conscious at any moment; let our attention be
withdrawn from it by some other object, and forthwith it disappears
from consciousness once more.

The only source of our knowledge of consciousness is that faculty
itself; that is the chief cause of the extraordinary difficulty of
subjecting it to scientific research. Subject and object are one and
the same in it: the perceptive subject mirrors itself in its own
inner nature, which is to be the object of our inquiry. Thus we can
never have a complete objective certainty of the consciousness of
others; we can only proceed by a comparison of their psychic condition
with our own. As long as this comparison is restricted to _normal_
people we are justified in drawing certain conclusions as to their
consciousness, the validity of which is unchallenged. But when we pass
on to consider _abnormal_ individuals (the genius, the eccentric, the
stupid, or the insane) our conclusions from analogy are either unsafe
or entirely erroneous. The same must be said with even greater truth
when we attempt to compare human consciousness with that of the animals
(even the higher, but especially the lower). In that case such grave
difficulties arise that the views of physiologists and philosophers
diverge as widely as the poles on the subject. We shall briefly
enumerate the most important of these views.

I. _The anthropistic theory of consciousness._--It is peculiar to man.
To Descartes we must trace the widespread notion that consciousness
and thought are man's exclusive prerogative, and that he alone is
blessed with an "immortal soul." This famous French philosopher and
mathematician (educated in a Jesuit College) established a rigid
partition between the psychic activity of man and that of the brute.
In his opinion the human soul, a thinking, immaterial being, is
completely separated from the body, which is extended and material.
Yet it is united to the body at a certain point in the brain (the
_glandula pinealis_) for the purpose of receiving impressions from the
outer world and effecting muscular movements. The animals, not being
endowed with thought, have no soul: they are mere automata, or cleverly
constructed machines, whose sensations, presentations, and volitions
are purely mechanical, and take place according to the ordinary laws
of physics. Hence Descartes was a _dualist_ in human psychology, and
a _monist_ in the psychology of the brute. This open contradiction in
so clear and acute a thinker is very striking; in explaining it, it
is not unnatural to suppose that he concealed his real opinion, and
left the discovery of it to independent scholars. As a pupil of the
Jesuits, Descartes had been taught to deny the truth in the face of his
better insight; and perhaps he dreaded the power and the fires of the
Church. Besides, his sceptical principle, that every sincere effort to
attain the truth must start with a doubt of the traditional dogma had
already drawn upon him fanatical accusations of scepticism and atheism.
The great influence which Descartes had on subsequent philosophy was
very remarkable, and entirely in harmony with his "book-keeping by
double entry." The _materialists_ of the seventeenth and eighteenth
centuries appealed to the Cartesian theory of the animal soul and its
purely mechanical activity in support of their monistic psychology. The
_spiritualists_, on the other hand, asserted that their dogma of the
immortality of the soul and its independence of the body was firmly
established by Descartes' theory of the human soul. This view is still
prevalent in the camp of the theologians and dualistic metaphysicians.
The scientific conception of nature, however, which has been built up
in the nineteenth century, has, with the aid of empirical progress, in
physiological and comparative psychology, completely falsified it.

II. _Neurological theory of consciousness._--It is present only
in man and those higher animals which have a centralized nervous
system and organs of sense. The conviction that a large number of
animals--at least the higher mammals--are not less endowed than man
with a thinking soul and consciousness prevails in modern zoology,
exact physiology, and the monistic psychology. The immense progress we
have made in the various branches of biology has contributed to bring
about a recognition of this important truth. We confine ourselves for
the present to the higher vertebrates, and especially the mammals.
That these most intelligent specimens of these highly developed
vertebrates--apes and dogs, in particular--have a strong resemblance to
man in their whole psychic life has been recognized and speculated on
for thousands of years. Their faculty of presentation and sensation,
of feeling and desire, is so like that of man that we need adduce no
proof of our thesis. But even the higher associational activity of
the brain, the formation of judgments and their connection into chains
of reasoning, thought, and consciousness in the narrower sense, are
developed in them after the same fashion as in man: they differ only in
degree, not in kind. Moreover, we learn from comparative anatomy and
histology that the intricate structure of the brain (both in general
and in detail) is substantially the same in the mammals as it is in
man. The same lesson is enforced by comparative ontogeny with regard
to the origin of these psychic organs. Comparative physiology teaches
us that the various states of consciousness are just the same in these
highest placentals as in man; and we learn by experiment that there
is the same reaction to external stimuli. The higher animals can be
narcotized by alcohol, chloroform, ether, etc., and may be hypnotized
by the usual methods, just as in the case of man.

It is, however, impossible to determine mathematically at what stage
of animal life consciousness is to be first recognized as such. Some
zoologists draw the line very high in the scale, others very low.
Darwin, who most accurately distinguishes the various stages of
consciousness, intelligence, and emotion in the higher animals, and
explains them by progressive evolution, points out how difficult,
or even impossible, it is to determine the first beginning of this
supreme psychic faculty in the lower animals. Personally, out of the
many contradictory theories, I take that to be most probable which
holds _the centralization of the nervous system_ to be a condition of
consciousness; and that is wanting in the lower classes of animals. The
presence of a central nervous organ, of highly developed sense-organs,
and an elaborate association of groups of presentations, seem to me to
be required before the unity of consciousness is possible.

III. _Animal theory of consciousness._--All animals, and they alone,
have consciousness. This theory would draw a sharp distinction between
the psychic life of the animal and of the plant. Such a distinction
was urged by many of the older writers, and was clearly formulated
by Linné in his celebrated _Systema Naturae_; the two great kingdoms
of the organic world are, in his opinion, divided by the fact that
animals have sensation and consciousness, and the plants are devoid
of them. Later on Schopenhauer laid stress on the same distinction:
"Consciousness is only known to us as a feature of animal nature.
Even though it extend upwards through the whole animal kingdom, even
to man and his reason, the unconsciousness of the plant, from which
it started, remains as the basic feature. In the lowest animals we
have but the dawn of it." The inaccuracy of this view was obvious by
about the middle of the present century, when a deeper study was made
of the psychic activity of the lower animal forms, especially the
coelenterates (sponges and cnidaria): they are undoubtedly animals,
yet there is no more trace of a definite consciousness in them than in
most of the plants. The distinction between the two kingdoms was still
further obliterated when more careful research was made into their
unicellular forms. There is no psychological difference between the
plasmophagous protozoa and the plasmodomous protophyta, even in respect
of their consciousness.

IV. _Biological theory of consciousness._--It is found in all
organisms, animal or vegetal, but not in lifeless bodies (such as
crystals). This opinion is usually associated with the idea that all
organisms (as distinguished from inorganic substances) have souls:
the three ideas--life, soul, and consciousness--are then taken to be
coextensive. Another modification of this view holds that, though
these fundamental phenomena of organic life are inseparably connected,
yet consciousness is only a part of the activity of the soul, and of
the vital activity. Fechner, in particular, has endeavored to prove
that the plant has a "soul," in the same sense as an animal is said
to have one; and many credit the vegetal soul with a consciousness
similar to that of the animal soul. In truth, the remarkable stimulated
movements of the leaves of the sensitive plants (the mimosa, drosera,
and dionæa), the automatic movements of other plants (the clover
and wood-sorrel, and especially the hedysarum), the movements of
the "sleeping plants" (particularly the _papilionacea_), etc., are
strikingly similar to the movements of the lower animal forms: whoever
ascribes consciousness to the latter cannot refuse it to such vegetal

V. _Cellular theory of consciousness._--It is a vital property of every
cell. The application of the cellular theory to every branch of biology
involved its extension to psychology. Just as we take the living cell
to be the "elementary organism" in anatomy and physiology, and derive
the whole system of the multicellular animal or plant from it, so, with
equal right, we may consider the "cell-soul" to be the psychological
unit, and the complex psychic activity of the higher organism to be
the result of the combination of the psychic activity of the cells
which compose it. I gave the outlines of this _cellular psychology_
in my _General Morphology_ in 1866, and entered more fully into the
subject in my paper on "Cell-Souls and Soul-Cells." I was led to a
deeper study of this "elementary psychology" by my protracted research
into the unicellular forms of life. Many of these tiny (generally
microscopic) protists show similar expressions of sensation and will,
and similar instincts and movements, to those of higher animals; that
is especially true of the very sensitive and lively infusoria. In the
relation of these sensitive cell-organisms to their environment, and in
many other of their vital expressions (for instance, in the wonderful
architecture of the rhizopods, the thalamophoræ, and the infusoria),
we seemed to have clear indications of conscious psychic action. If,
then, we accept the biological theory of consciousness (No. IV.), and
credit every psychic function with a share of that faculty, we shall be
compelled to ascribe it to each independent protist cell. In that case
its material basis would be either the entire protoplasm of the cell,
or its nucleus, or a portion of it. In the "psychade theory" of Fritz
Schultze the elementary consciousness of the _psychade_ would have
the same relation to the individual cells as personal consciousness
has to the multicellular organism of the personality in the higher
animals and man. It is impossible definitively to disprove this theory,
which I held at one time. Still, I now feel compelled to agree with
Max Verworn, in his belief that none of the protists have a developed
self-consciousness, but that their sensations and movements are of an
unconscious character.

VI. _Atomistic theory of consciousness._--It is an elementary property
of all atoms. This atomistic hypothesis goes furthest of all the
different views as to the extension of consciousness. It certainly
escapes the difficulty which so many philosophers and biologists
experience in solving the problem of the first origin of consciousness.
It is a phenomenon of so peculiar a character that a derivation of
it from other psychic functions seems extremely hazardous. It seemed,
therefore, the easiest way out of the difficulty to conceive it as an
inherent property of all matter, like gravitation or chemical affinity.
On that hypothesis there would be as many forms of this original
consciousness as there are chemical elements; each atom of hydrogen
would have its hydrogenic consciousness, each atom of carbon its
carbonic consciousness, and so forth. There are philosophers, even, who
ascribe consciousness to the four elements of Empedocles, the union of
which, by "love and hate," produces the totality of things.

Personally, I have never subscribed to this hypothesis of atomic
consciousness. I emphasize the point because Emil du Bois-Reymond
has attributed it to me. In the controversy I had with him (1880) he
violently attacked my "pernicious and false philosophy," and contended
that I had, in my paper on "The Perigenesis of the Plastidule," "laid
it down as a metaphysical axiom that every atom has its individual
consciousness." On the contrary, I explicitly stated that I conceive
the elementary psychic qualities of sensation and will, which may
be attributed to atoms, to be _unconscious_--just as unconscious as
the elementary memory which I, in company with that distinguished
physiologist, Ewald Hering, consider to be "a common function of
all organized matter"--or, more correctly, "living substance." Du
Bois-Reymond curiously confuses "soul" and "consciousness"; whether
from oversight or not I cannot say. Since he considers consciousness
to be a transcendental phenomenon (as we shall see presently), while
denying that character to other psychic functions--the action of the
senses, for example--I must infer that he recognizes the difference
of the two ideas. Other parts of his eloquent speeches contain quite
the opposite view, for the famous orator not infrequently contradicts
himself on important questions of principle. However, I repeat that, in
my opinion, consciousness is only _part_ of the psychic phenomena which
we find in man and the higher animals; the great majority of them are

However divergent are the different views as to the nature and
origin of consciousness, they may, nevertheless, on a clear and
logical examination, all be reduced to two fundamental theories--the
transcendental (or dualistic) and the physiological (or monistic).
I have myself always held the latter view, in the light of my
evolutionary principles, and it is now shared by a great number of
distinguished scientists, though it is by no means generally accepted.
The transcendental theory is the older and much more common; it
has recently come once more into prominence, principally through
Du Bois-Reymond, and it has acquired a great importance in modern
discussions of cosmic problems through his famous "Ignorabimus speech."
On account of the extreme importance of this fundamental question we
must touch briefly on its main features.

In the celebrated discourse on "The Limits of Natural Science,"
which E. du Bois-Reymond gave on August 14, 1872, at the Scientific
Congress at Leipzig, he spoke of two "absolute limits" to our possible
knowledge of nature which the human mind will never transcend in its
most advanced science--_never_, as the oft-quoted termination of the
address, "Ignorabimus," emphatically pronounces. The first absolutely
insoluble "world-enigma" is the "connection of matter and force," and
the distinctive character of these fundamental natural phenomena; we
shall go more fully into this "problem of substance" in the twelfth
chapter. The second insuperable difficulty of philosophy is given as
the problem of consciousness--the question how our mental activity
is to be explained by material conditions, especially movements, how
"substance [the substance which underlies matter and force] comes,
under certain conditions, to feel, to desire, and to think."

For brevity, and in order to give a characteristic name to the Leipzig
discourse, I have called it the "Ignorabimus speech"; this is the
more permissible, as E. du Bois-Reymond himself, with a just pride,
eight years afterwards, speaking of the extraordinary consequences
of his discourse, said: "Criticism sounded every possible note, from
friendly praise to the severest censure, and the word 'Ignorabimus,'
which was the culmination of my inquiry, was at once transformed into a
kind of scientific shibboleth." It is quite true that loud praise and
approbation resounded in the halls of the dualistic and spiritualistic
philosophy, and especially in the camp of the "Church militant"; even
the spiritists and the host of believers, who thought the immortality
of their precious souls was saved by the "Ignorabimus," joined in the
chorus. The "severest censure" came at first only from a few scientists
and philosophers--from the few who had sufficient scientific knowledge
and moral courage to oppose the dogmatism of the all-powerful secretary
and dictator of the Berlin Academy of Science.

Towards the end, however, the author of the "Ignorabimus speech" briefly
alluded to the question whether these two great "world-enigmas," the
general problem of substance and the special problem of consciousness,
are not two aspects of one and the same problem. "This idea," he said,
"is certainly the simplest, and preferable to the one which makes the
world doubly incomprehensible. Such, however, is the nature of things
that even here we can obtain no clear knowledge, and it is useless to
speak further of the question." The latter sentiment I have always
stoutly contested, and have endeavored to prove that the two great
questions are not two distinct problems. "The neurological problem
of consciousness is but a particular aspect of the all-pervading
cosmological problem of substance."

The peculiar phenomenon of consciousness is not, as Du Bois-Reymond
and the dualistic school would have us believe, a completely
"transcendental" problem; it is, as I showed thirty-three years ago,
a _physiological_ problem, and, as such, must be reduced to the
phenomena of physics and chemistry. I subsequently gave it the more
definite title of a _neurological_ problem, as I share the view that
true consciousness (thought and reason) is only present in those higher
animals which have a centralized nervous system and organs of sense
of a certain degree of development. Those conditions are certainly
found in the higher vertebrates, especially in the placental mammals,
the class from which man has sprung. The consciousness of the highest
apes, dogs, elephants, etc., differs from that of man in degree only,
not in kind, and the graduated interval between the consciousness of
these "rational" placentals and that of the lowest races of men (the
Veddahs, etc.) is less than the corresponding interval between these
uncivilized races and the highest specimens of thoughtful humanity
(Spinoza, Goethe, Lamarck, Darwin, etc.). Consciousness is but a part
of the higher activity of the soul, and as such it is dependent on the
normal structure of the corresponding psychic organ, the brain.

Physiological observation and experiment determined twenty years ago
that the particular portion of the mammal-brain which we call the
_seat_ (preferably the _organ_) of consciousness is a part of the
cerebrum, an area in the late-developed gray bed, or cortex, which
is evolved out of the convex dorsal portion of the primary cerebral
vesicle, the "fore-brain." Now, the morphological proof of this
physiological thesis has been successfully given by the remarkable
progress of the microscopic anatomy of the brain, which we owe to the
perfect methods of research of modern science (Kölliker, Flechsig,
Golgi, Edinger, Weigert, and others).

The most important development is the discovery of the _organs of
thought_ by Paul Flechsig, of Leipzig; he proved that in the gray bed
of the brain are found the four seats of the central sense-organs,
or four "inner spheres of sensation"--the sphere of touch in the
vertical lobe, the sphere of smell in the frontal lobe, the sphere
of sight in the occipital lobe, and the sphere of hearing in the
temporal lobe. Between these four "sense-centres" lie the four great
"thought-centres," or centres of association, the _real organs of
mental life_; they are those highest instruments of psychic activity
that produce thought and consciousness. In front we have the frontal
brain or centre of association; behind, on top there is the vertical
brain, or parietal centre of association, and underneath the principal
brain, or "the great occipito-temporal centre of association" (the
most important of all); lower down, and internally, the insular brain
or the insula of Reil, the insular centre of association. These four
"thought-centres," distinguished from the intermediate "sense-centres"
by a peculiar and elaborate nerve-structure, are the true and sole
organs of thought and consciousness. Flechsig has recently pointed out
that, in the case of man, very specific structures are found in one
part of them; these structures are wanting in the other mammals, and
they, therefore, afford an explanation of the superiority of man's
mental powers.

The momentous announcement of modern physiology, that the cerebrum is
the organ of consciousness and mental action in man and the higher
mammals, is illustrated and confirmed by the pathological study of
its diseases. When parts of the cortex are destroyed by disease their
respective functions are affected, and thus we are enabled, to some
extent, to localize the activities of the brain; when certain parts
of the area are diseased, that portion of thought and consciousness
disappears which depends on those particular sections. Pathological
experiment yields the same result; the decay of some known area (for
instance, the centre of speech) extinguishes its function (speech).
In fact, there is proof enough in the most familiar phenomena of
consciousness of their complete dependence on chemical changes in
the substance of the brain. Many beverages (such as coffee and
tea) stimulate our powers of thought; others (such as wine and
beer) intensify feeling; musk and camphor reanimate the fainting
consciousness; ether and chloroform deaden it, and so forth. How
would that be possible if consciousness were an immaterial entity,
independent of these anatomical organs? And what becomes of the
consciousness of the "immortal soul" when it no longer has the use of
these organs?

These and other familiar facts prove that man's consciousness--and
that of the nearest mammals--is _changeable_, and that its activity
is always open to modification from inner (alimentation, circulation,
etc.) and outer causes (lesion of the brain, stimulation, etc.).
Very instructive, too, are the facts of double and intermittent
consciousness, which remind us of "alternate generations of
presentations." The same individual has an entirely different
consciousness on different days, with a change of circumstances; he
does not know to-day what he did yesterday: yesterday he could say, "I
am I"; to-day he must say, "I am another being." Such intermittence of
consciousness may last not only days, but months, and even years; the
change may even become permanent.

As everybody knows, the new-born infant has no consciousness. Preyer
has shown that it is only developed after the child has begun to
speak; for a long time it speaks of itself in the third person.
In the important moment when it first pronounces the word "I,"
when the feeling of self becomes clear, we have the beginning of
self-consciousness, and of the antithesis to the non-ego. The rapid
and solid progress in knowledge which the child makes in its first
ten years, under the care of parents and teachers, and the slower
progress of the second decade, until it reaches complete maturity of
mind, are intimately connected with a great advancement in the growth
and development of consciousness and of its organ, the brain. But even
when the pupil has got his "certificate of maturity" his consciousness
is still far from mature; it is then that his "world-consciousness"
first begins to develop, in his manifold relations with the outer
world. Then, in the third decade, we have the full maturity of rational
thought and consciousness, which, in cases of normal development, yield
their ripe fruits during the next three decades. The slow, gradual
degeneration of the higher mental powers, which characterizes senility,
usually sets in at the commencement of the seventh decade--sometimes
earlier, sometimes later. Memory, receptiveness, and interest in
particular objects gradually decay; though productivity, mature
consciousness, and philosophic interest in general truths often remain
for many years longer.

The individual development of consciousness in earlier youth proves the
universal validity of the _biogenetic law_; and, indeed, it is still
recognizable in many ways during the later years. In any case, the
ontogenesis of consciousness makes it perfectly clear that it is not
an "immaterial entity," but a physiological function of the brain, and
that it is, consequently, no exception to the general law of substance.

From the fact that consciousness, like all other psychic functions,
is dependent on the normal development of certain organs, and that
it gradually unfolds in the child in proportion to the development
of those organs, we may already conclude that it has arisen in the
animal kingdom by a gradual historical development. Still, however
certain we are of the fact of this natural evolution of consciousness,
we are, unfortunately, not yet in a position to enter more deeply
into the question and construct special hypotheses in elucidation
of it. Palæontology, it is true, gives us a few facts which are not
without significance. For instance, the quantitative and qualitative
development of the brain of the placental mammals during the Tertiary
period is very remarkable. The cavity of many of the fossil skulls of
the period has been carefully examined, and has given us a good deal of
reliable information as to the size, and, to some extent, as to the
structure, of the brain they enclosed. We find, within the limits of
one and the same group (the ungulates, the rodents, or the primates), a
marked advance in the later miocene and pliocene specimens as compared
with the earlier eocene and oligocene representatives of the same stem;
in the former the brain (in proportion to the size of the organism) is
six to eight times as large as in the latter.

Moreover, that highest stage of consciousness, which is reached by man
alone, has been evolved step by step--even by the very progress of
civilization--from a lower condition, as we find illustrated to-day in
the case of uncivilized races. That is easily proved by a comparison
of their languages, which is closely connected with the comparison of
their ideas. The higher the conceptual faculty advances in thoughtful
civilized man, the more qualified he is to detect common features amid
a multitude of details, and embody them in general concepts, and so
much the clearer and deeper does his consciousness become.



    The Citadel of Superstition--Athanatism and Thanatism--Individual
    Character of Death--Immortality of the Unicellular Organisms
    (Protists)--Cosmic and Personal Immortality--Primary Thanatism (of
    Uncivilized Peoples)--Secondary Thanatism (of Ancient and Recent
    Philosophers)--Athanatism and Religion--Origin of the Belief
    in Immortality--Christian Athanatism--Eternal Life--The Day of
    Judgment--Metaphysical Athanatism--Substance of the Soul--Ether
    Souls and Air Souls; Fluid Souls and Solid Souls--Immortality of
    the Animal Soul--Arguments for and Against Athanatism--Athanatist

When we turn from the genetic study of the soul to the great question
of its immortality, we come to that highest point of superstition which
is regarded as the impregnable citadel of all mystical and dualistic
notions. For in this crucial question, more than in any other problem,
philosophic thought is complicated by the selfish interest of the human
personality, who is determined to have a guarantee of his existence
beyond the grave at any price. This "higher necessity of feeling" is
so powerful that it sweeps aside all the logical arguments of critical
reason. Consciously or unconsciously, most men are influenced in all
their general views, and, therefore, in their theory of life, by the
dogma of personal immortality; and to this theoretical error must be
added practical consequences of the most far-reaching character. It is
our task, therefore, to submit every aspect of this important dogma to
a critical examination, and to prove its untenability in the light of
the empirical data of modern biology.

In order to have a short and convenient expression for the two opposed
opinions on the question, we shall call the belief in man's personal
immortality "athanatism" (from _athanes_ or _athanatos_ == immortal).
On the other hand, we give the name of "thanatism" (from _thanatos_
== death) to the opinion which holds that at a man's death not only
all the other physiological functions are arrested, but his "soul"
also disappears--that is, that sum of cerebral functions which psychic
dualism regards as a peculiar entity, independent of the other vital
processes in the living body.

In approaching this physiological problem of death we must point out
the _individual_ character of this organic phenomenon. By death we
understand simply the definitive cessation of the vital activity of
the _individual_ organism, no matter to which category or stage of
individuality the organism in question belongs. Man is dead when his
own personality ceases to exist, whether he has left offspring that
they may continue to propagate for many generations or not. In a
certain sense we often say that the minds of great men (in a dynasty
of eminent rulers, for instance, or a family of talented artists) live
for many generations; and in the same way we speak of the "soul" of
a noble woman living in her children and children's children. But in
these cases we are dealing with intricate phenomena of _heredity_,
in which a microscopic cell (the sperm-cell of the father or the
egg-cell of the mother) transmits certain features to offspring. The
particular personalities who produce those sexual cells in thousands
are mortal beings, and at their death their personal psychic activity
is extinguished like every other physiological function.

A number of eminent zoologists--Weismann being particularly
prominent--have recently defended the opinion that only the lowest
unicellular organisms, the protists, are immortal, in contradistinction
to the multicellular plants and animals, whose bodies are formed of
tissues. This curious theory is especially based on the fact that
most of the protists multiply without sexual means, by division or
the formation of spores. In such processes the whole body of the
unicellular organism breaks up into two or more equal parts (daughter
cells), and each of these portions completes itself by further growth
until it has the size and form of the mother cell. However, by the very
process of division the _individuality_ of the unicellular creature
has been destroyed; both its physiological and its morphological unity
have gone. The view of Weismann is logically inconsistent with the
very notion of _individual_--an "indivisible" entity; for it implies
a unity which cannot be divided without destroying its nature. In
this sense the unicellular protophyta and protozoa are throughout
life _physiological individuals_, just as much as the multicellular
tissue-plants and animals. A sexual propagation by simple division
is found in many of the multicellular species (for instance, in many
cnidaria, corals, medusæ, etc.); the mother animal, the division of
which gives birth to the two daughter animals, ceases to exist with
the segmentation. "The protozoa," says Weismann, "have no individuals
and no generations in the metazoic sense." I must entirely dissent
from his thesis. As I was the first to introduce the title of
_metazoa_, and oppose these multicellular, tissue-forming animals to
the unicellular _protozoa_ (infusoria, rhizopods, etc.), and as I was
the first to point out the essential difference in the development of
the two (the former from germinal layers, and the latter not), I must
protest that I consider the _protozoa_ to be just as mortal in the
physiological (and psychological) sense as the _metazoa_; neither body
nor soul is immortal in either group. The other erroneous consequences
of Weismann's notion have been refuted by Moebius (1884), who justly
remarks that "every event in the world is periodic," and that "there is
no source from which immortal organic individuals might have sprung."

When we take the idea of immortality in the widest sense, and extend
it to the totality of the knowable universe, it has a scientific
significance; it is then not merely acceptable, but self-evident,
to the monistic philosopher. In that sense the thesis of the
indestructibility and eternal duration of all that exists is equivalent
to our supreme law of nature, the _law of substance_ (see chap. xii).
As we intend to discuss this immortality of the cosmos fully later on,
in establishing the theory of the persistence of matter and force,
we shall not dilate on it at present. We pass on immediately to the
criticism of that belief in immortality which is the only sense usually
attached to the word, the immortality of the individual soul. We
shall first inquire into the extent and the origin of this mystic and
dualistic notion, and point out, in particular, the wide acceptance
of the contradictory thesis, our monistic, empirically established
_thanatism_. I must distinguish two essentially different forms of
thanatism--primary and secondary; primary thanatism is the original
absence of the dogma of immortality (in the primitive uncivilized
races); secondary thanatism is the later outcome of a rational
knowledge of nature in the civilized intelligence.

We still find it asserted in philosophic, and especially in theological,
works that belief in the personal immortality of the human soul was
originally shared by all men--or, at least, by all "rational" men. That
is not the case. This dogma is not an original idea of the human mind,
nor has it ever found universal acceptance. It has been absolutely
proved by modern comparative ethnology that many uncivilized races
of the earliest and most primitive stage had no notion either of
immortality or of God. That is true, for instance, of the Veddahs of
Ceylon, those primitive pygmies whom, on the authority of the able
studies of the Sarasins, we consider to be a relic of the earliest
inhabitants of India;[22] it is also the case in several of the
earliest groups of the nearly related Dravidas, the Indian Seelongs,
and some native Australian races. Similarly, several of the primitive
branches of the American race, in the interior of Brazil, on the upper
Amazon, etc., have no knowledge either of gods or immortality. This
_primary_ absence of belief in immortality and deity is an extremely
important fact; it is, obviously, easy to distinguish from the
_secondary_ absence of such belief, which has come about in the highest
civilized races as the result of laborious critico-philosophical study.

Differently from the primary thanatism which originally characterized
primitive man, and has always been widely spread, the _secondary_
absence of belief in immortality is only found at a late stage of
history: it is the ripe fruit of profound reflection on life and death,
the outcome of bold and independent philosophical speculation. We first
meet it in some of the Ionic philosophers of the sixth century B.C.,
then in the founders of the old materialistic philosophy, Democritus
and Empedocles, and also in Simonides and Epicurus, Seneca and Plinius,
and in an elaborate form in Lucretius Carus. With the spread of
Christianity at the decay of classical antiquity, athanatism, one of
its chief articles of faith, dominated the world, and so, amid other
forms of superstition, the myth of personal immortality came to be
invested with a high importance.

Naturally, through the long night of the Dark Ages it was rarely that
a brave free-thinker ventured to express an opinion to the contrary:
the examples of Galileo, Giordano Bruno, and other independent
philosophers, effectually destroyed all freedom of utterance. Heresy
only became possible when the Reformation and the Renaissance had
broken the power of the papacy. The history of modern philosophy tells
of the manifold methods by which the matured mind of man sought to
rid itself of the superstition of immortality. Still, the intimate
connection of the belief with the Christian dogma invested it with
such power, even in the more emancipated sphere of Protestantism,
that the majority of convinced free-thinkers kept their sentiments to
themselves. From time to time some distinguished scholar ventured to
make a frank declaration of his belief in the impossibility of the
continued life of the soul after death. This was done in France in the
second half of the eighteenth century by Voltaire, Danton, Mirabeau,
and others, and by the leaders of the materialistic school of those
days, Holbach, Lamettrie, etc. The same opinion was defended by the
able friend of the Materialists, the greatest of the Hohenzollerns, the
monistic "philosopher of Sans-souci." What would Frederick the Great,
the "crowned thanatist and atheist," say, could he compare his monistic
views with those of his successor of to-day?

Among thoughtful physicians the conviction that the existence of the
soul came to an end at death has been common for centuries: generally,
however, they refrained from giving it expression. Moreover, the
empirical science of the brain remained so imperfect during the last
century that the soul could continue to be regarded as its mysterious
inhabitant. It was the gigantic progress of biology in the present
century, and especially in the latter half of the century, that
finally destroyed the myth. The establishment of the theory of descent
and the cellular theory, the astounding discoveries of ontogeny and
experimental physiology--above all, the marvellous progress of the
microscopic anatomy of the brain, gradually deprived athanatism of
every basis; now, indeed, it is rarely that an informed and honorable
biologist is found to defend the immortality of the soul. All the
monistic philosophers of the century (Strauss, Feuerbach, Büchner,
Spencer, etc.) are thanatists.

The dogma of personal immortality owes its great popularity and its
high importance to its intimate connection with the teaching of
Christianity. This circumstance gave rise to the erroneous and still
prevalent belief that the myth is a fundamental element of all the
higher religions. That is by no means the case. The higher Oriental
religions include no belief whatever in the immortality of the soul;
it is not found in Buddhism, the religion that dominates thirty per
cent. of the entire human race; it is not found in the ancient popular
religion of the Chinese, nor in the reformed religion of Confucius
which succeeded it; and, what is still more significant, it is not
found in the earlier and purer religion of the Jews. Neither in the
"five Mosaic books," nor in any of the writings of the Old Testament
which were written before the Babylonian Exile, is there any trace of
the notion of individual persistence after death.

The mystic notion that the human soul will live forever after death has
had a polyphyletic origin. It was unknown to the earliest speaking man
(the hypothetical _homo primigenius_ of Asia), to his predecessors, of
course, the _pithecanthropus_ and _prothylobates_, and to the least
developed of his modern successors, the Veddahs of Ceylon, the Seelongs
of India, and other distant races. With the development of reason and
deeper reflection on life and death, sleep and dreams, mystic ideas of
a dualistic composition of our nature were evolved--independently of
each other--in a number of the earlier races. Very different influences
were at work in these polyphyletic creations--worship of ancestors,
love of relatives, love of life and desire of its prolongation, hope of
better conditions of life beyond the grave, hope of the reward of good
and punishment of evil deeds, and so forth. Comparative psychology has
recently brought to our knowledge a great variety of myths and legends
of that character; they are, for the most part, closely associated
with the oldest forms of theistic and religious belief. In most of the
modern religions athanatism is intimately connected with theism; the
majority of believers transfer their materialistic idea of a "personal
God" to their "immortal soul." That is particularly true of the
dominant religion of modern civilized states, Christianity.

As everybody knows, the dogma of the immortality of the soul has long
since assumed in the Christian religion that rigid form which it
has in the articles of faith: "I believe in the resurrection of the
body and in an eternal life." Man will arise on "the last day," as
Christ is alleged to have done on Easter morn, and receive a reward
according to the tenor of his earthly life. This typically Christian
idea is thoroughly materialistic and anthropomorphic; it is very little
superior to the corresponding crude legends of uncivilized peoples. The
impossibility of "the resurrection of the body" is clear to every man
who has some knowledge of anatomy and physiology. The resurrection of
Christ, which is celebrated every Easter by millions of Christians, is
as purely mythical as "the awakening of the dead," which he is alleged
to have taught. These mystic articles of faith are just as untenable in
the light of pure reason as the cognate hypothesis of "eternal life."

The fantastic notions which the Christian Church disseminates as to the
eternal life of the immortal soul after the dissolution of the body are
just as materialistic as the dogma of "the resurrection of the body."
In his interesting work on _Religion in the Light of the Darwinian
Theory_, Savage justly remarks: "It is one of the standing charges of
the Church against science that it is materialistic. I must say, in
passing, that the whole ecclesiastical doctrine of a future life has
always been, and still is, materialism of the purest type. It teaches
that the material body shall rise, and dwell in a material heaven." To
prove this one has only to read impartially some of the sermons and
ornate discourses in which the glory of the future life is extolled
as the highest good of the Christian, and belief in it is laid down to
be the foundation of morality. According to them, all the joys of the
most advanced modern civilization await the pious believer in Paradise,
while the "All-loving Father" reserves his eternal fires for the
godless materialist.

In opposition to the materialist athanatism, which is dominant in
the Christian and Mohammedan Churches, we have, apparently, a purer
and higher form of faith in the _metaphysical athanatism_, as taught
by most of our dualist and spiritualist philosophers. Plato must be
considered its chief creator: in the fourth century before Christ
he taught that complete dualism of body and soul which afterwards
became one of the most important, theoretically, and one of the most
influential, practically, of the Christian articles of faith. The
body is mortal, material, physical; the soul is immortal, immaterial,
metaphysical. They are only temporarily associated, for the course of
the individual life. As Plato postulated an eternal life before as well
as after this temporary association, he must be classed as an adherent
of "metempsychosis," or transmigration of souls; the soul existed as
such, or as an "eternal idea," before it entered into a human body.
When it quits one body it seeks such other as is most suited to its
character for its habitation. The souls of bloody tyrants pass into the
bodies of wolves and vultures, those of virtuous toilers migrate into
the bodies of bees and ants, and so forth. The childish naïvety of this
Platonic morality is obvious; on closer examination his views are found
to be absolutely incompatible with the scientific truth which we owe to
modern anatomy, physiology, histology, and ontogeny; we mention them
only because, in spite of their absurdity, they have had a profound
influence on thought and culture. On the one hand, the mysticism of the
Neo-Platonists, which penetrated into Christianity, attaches itself to
the psychology of Plato; on the other hand, it became subsequently one
of the chief supports of spiritualistic and idealistic philosophy. The
Platonic "idea" gave way in time to the notion of psychic "substance";
this is just as incomprehensible and metaphysical, though it often
assumed a physical appearance.

The conception of the soul as a "substance" is far from clear in many
psychologists; sometimes it is regarded as an "immaterial" entity of
a peculiar character in an abstract and idealistic sense, sometimes
in a concrete and realistic sense, and sometimes as a confused
_tertium quid_ between the two. If we adhere to the monistic idea of
substance, which we develop in chap. xii., and which takes it to be
the simplest element of our whole world-system, we find _energy_ and
_matter_ inseparably associated in it. We must, therefore, distinguish
in the "substance of the soul" the characteristic psychic _energy_
which is all we perceive (sensation, presentation, volition, etc.),
and the psychic _matter_, which is the inseparable basis of its
activity--that is, the living protoplasm. Thus, in the higher animals
the "matter" of the soul is a part of the nervous system; in the lower
nerveless animals and plants it is a part of their multicellular
protoplasmic body; and in the unicellular protists it is a part of
their protoplasmic cell-body. In this way we are brought once more
to the psychic organs, and to an appreciation of the fact that these
material organs are indispensable for the action of the soul; but the
soul itself is _actual_--it is the sum-total of their physiological

However, the idea of a specific "soul-substance" found in the
dualistic philosophers who admit such a thing is very different from
this. They conceive the immortal soul to be material, yet invisible,
and essentially different from the visible body which it inhabits.

Thus _invisibility_ comes to be regarded as a most important attribute
of the soul. Some, in fact, compare the soul with ether, and regard
it, like ether, as an extremely subtle, light, and highly elastic
material, an imponderable agency, that fills the intervals between the
ponderable particles of the living organism, others compare the soul
with the wind, and so give it a gaseous nature; and it is this simile
which first found favor with primitive peoples, and led in time to the
familiar dualistic conception. When a man died, the body remained as a
lifeless corpse, but the immortal soul "flew out of it with the last

The comparison of the human soul with physical ether as a qualitatively
similar idea has assumed a more concrete shape in recent times through
the great progress of optics and electricity (especially in the last
decade); for these sciences have taught us a good deal about the
energy of ether, and enabled us to formulate certain conclusions as
to the material character of this all-pervading agency. As I intend
to describe these important discoveries later on (in chap. xii.), I
shall do no more at present than briefly point out that they render
the notion of an "etheric soul" absolutely untenable. Such an etheric
soul--that is a psychic substance--which is similar to physical ether,
and which, like ether, passes between the ponderable elements of the
living protoplasm or the molecules of the brain, cannot possibly
account for the individual life of the soul. Neither the mystic
notions of that kind which were warmly discussed about the middle
of the century, nor the attempts of modern "Neovitalists" to put
their mystical "vital force" on a line with physical ether, call for
refutation any longer.

Much more widespread, and still much respected, is the view which
ascribes a gaseous nature to the substance of the soul. The comparison
of human breath with the wind is a very old one; they were originally
considered to be identical, and were both given the same name. The
_anemos_ and _psyche_ of the Greeks, and the _anima_ and _spiritus_
of the Romans, were originally all names for "a breath of wind"; they
were transferred from this to the breath of man. After a time this
"living breath" was identified with the "vital force," and finally it
came to be regarded as the soul itself, or, in a narrower sense, as its
highest manifestation, the "spirit." From that the imagination went on
to derive the mystic notion of individual "spirits"; these, also, are
still usually conceived as "aëriform beings"--though they are credited
with the physiological functions of an organism, and they have been
photographed in certain well-known spiritist circles.

Experimental physics has succeeded, during the last decade of the
century, in reducing all gaseous bodies to a liquid--most of them,
also, to a solid--condition. Nothing more is needed than special
apparatus, which exerts a violent pressure on the gases at a very low
temperature. By this process not only the atmospheric elements, oxygen,
hydrogen, and nitrogen, but even compound gases (such as carbonic-acid
gas) and gaseous aggregates (like the atmosphere) have been changed
from gaseous to liquid form. In this way the "invisible" substances
have become "visible" to all, and in a certain sense "tangible."
With this transformation the mystic nimbus which formerly veiled
the character of the gas in popular estimation--as an invisible body
that wrought visible effects--has entirely disappeared. If, then, the
substance of the soul were really gaseous, it should be possible to
liquefy it by the application of a high pressure at a low temperature.
We could then catch the soul as it is "breathed out" at the moment of
death, condense it, and exhibit it in a bottle as "immortal fluid"
(_Fluidum animae immortale_). By a further lowering of temperature and
increase of pressure it might be possible to solidify it--to produce
"soul-snow." The experiment has not yet succeeded.

If athanatism were true, if, indeed, the human soul were to live for
all eternity, we should have to grant the same privilege to the souls
of the higher animals, at least to those of the nearest related mammals
(apes, dogs, etc.). For man is not distinguished from them by a special
_kind_ of soul, or by any peculiar and exclusive psychic function,
but only by a higher _degree_ of psychic activity, a superior stage
of development. In particular, consciousness--the function of the
association of ideas, thought, and reason--has reached a higher level
in many men (by no means in all) than in most of the animals. Yet this
difference is far from being so great as is popularly supposed; and it
is much slighter in every respect than the corresponding difference
between the higher and the lower animal souls, or even the difference
between the highest and the lowest stages of the human soul itself. If
we ascribe "personal immortality" to man, we are bound to grant it also
to the higher animals.

It is, therefore, quite natural that we should find this belief in
the immortality of the animal soul among many ancient and modern
peoples; we even meet it sometimes to-day in many thoughtful men
who postulate an "immortal life" for themselves, and have, at the
same time, a thorough empirical knowledge of the psychic life of the
animals. I once knew an old head-forester, who, being left a widower
and without children at an early age, had lived alone for more than
thirty years in a noble forest of East Prussia. His only companions
were one or two servants, with whom he exchanged merely a few necessary
words, and a great pack of different kinds of dogs, with which he
lived in perfect psychic communion. Through many years of training
this keen observer and friend of nature had penetrated deep into the
individual souls of his dogs, and he was as convinced of their personal
immortality as he was of his own. Some of his most intelligent dogs
were, in his impartial and objective estimation, at a higher stage of
psychic development than his old, stupid maid and the rough, wrinkled
manservant. Any unprejudiced observer, who will study the conscious
and intelligent psychic activity of a fine dog for a year, and follow
attentively the physiological processes of its thought, judgment,
and reason, will have to admit that it has just as valid a claim to
immortality as man himself.

The proofs of the immortality of the soul, which have been adduced for
the last two thousand years, and are, indeed, still credited with some
validity, have their origin, for the most part, not in an effort to
discover the truth, but in an alleged "necessity of emotion"--that is,
in imagination and poetic conceit. As Kant puts it, the immortality of
the soul is not an object of pure reason, but a "postulate of practical
reason." But we must set "practical reason" entirely aside, together
with all the "exigencies of emotion, or of moral education, etc.," when
we enter upon an honest and impartial pursuit of truth; for we shall
only attain it by the work of pure reason, starting from empirical
data and capable of logical analysis. We have to say the same of
athanatism as of theism; both are creations of poetic mysticism and of
transcendental "faith," not of rational science.

When we come to analyze all the different proofs that have been urged
for the immortality of the soul, we find that not a single one of them
is of a scientific character; not a single one is consistent with the
truths we have learned in the last few decades from physiological
psychology and the theory of descent. The _theological_ proof--that
a personal creator has breathed an immortal soul (generally regarded
as a portion of the divine soul) into man--is a pure myth. The
_cosmological_ proof--that the "moral order of the world" demands
the eternal duration of the human soul--is a baseless dogma. The
_teleological_ proof--that the "higher destiny" of man involves the
perfecting of his defective, earthly soul beyond the grave--rests
on a false anthropism. The _moral_ proof--that the defects and
the unsatisfied desires of earthly existence must be fulfilled by
"compensative justice" on the other side of eternity--is nothing
more than a pious wish. The _ethnological_ proof--that the belief in
immortality, like the belief in God, is an innate truth, common to
all humanity--is an error in fact. The _ontological_ proof--that the
soul, being a "simple, immaterial, and indivisible entity," cannot be
involved in the corruption of death--is based on an entirely erroneous
view of the psychic phenomena; it is a spiritualistic fallacy. All
these and similar "proofs of athanatism" are in a parlous condition;
they are definitely annulled by the scientific criticism of the last
few decades.

The extreme importance of the subject leads us to oppose to these
untenable "proofs of immortality" a brief exposition of the sound
scientific arguments against it. The _physiological_ argument shows
that the human soul is not an independent, immaterial substance, but,
like the soul of all the higher animals, merely a collective title
for the sum-total of man's cerebral functions; and these are just
as much determined by physical and chemical processes as any of the
other vital functions, and just as amenable to the law of substance.
The _histological_ argument is based on the extremely complicated
microscopic structure of the brain; it shows us the true "elementary
organs of the soul" in the ganglionic cells. The _experimental_
argument proves that the various functions of the soul are bound up
with certain special parts of the brain, and cannot be exercised unless
these are in a normal condition; if the areas are destroyed, their
function is extinguished; and this is especially applicable to the
"organs of thought," the four central instruments of mental activity.
The _pathological_ argument is the complement of the physiological;
when certain parts of the brain (the centres of speech, sight,
hearing, etc.) are destroyed by sickness, their activity (speech,
vision, hearing, etc.) disappears; in this way nature herself makes
the decisive physiological experiment. The _ontogenetic_ argument
puts before us the facts of the development of the soul in the
individual; we see how the child-soul gradually unfolds its various
powers; the youth presents them in full bloom, the mature man shows
their ripe fruit; in old age we see the gradual decay of the psychic
powers, corresponding to the senile degeneration of the brain. The
_phylogenetic_ argument derives its strength from palæontology, and the
comparative anatomy and physiology of the brain; co-operating with and
completing each other, these sciences prove to the hilt that the human
brain (and, consequently, its function--the soul) has been evolved step
by step from that of the mammal, and, still further back, from that of
the lower vertebrate.

These inquiries, which might be supplemented by many other results of
modern science, prove the old dogma of the immortality of the soul
to be absolutely untenable; in the twentieth century it will not be
regarded as a subject of serious scientific research, but will be left
wholly to transcendental "faith." The "critique of pure reason" shows
this treasured faith to be a mere _superstition_, like the belief in a
personal God which generally accompanies it. Yet even to-day millions
of "believers"--not only of the lower, uneducated masses, but even of
the most cultured classes--look on this superstition as their dearest
possession and their most "priceless treasure." It is, therefore,
necessary to enter more deeply into the subject, and--assuming it to
be true--to make a critical inquiry into its practical value. It soon
becomes apparent to the impartial critic that this value rests, for
the most part, on fancy, on the want of clear judgment and consecutive
thought. It is my firm and honest conviction that a definitive
abandonment of these "athanatist illusions" would involve no painful
loss, but an inestimable positive gain for humanity.

Man's "emotional craving" clings to the belief on immortality for two
main reasons: firstly, in the hope of better conditions of life beyond
the grave; and, secondly, in the hope of seeing once more the dear
and loved ones whom death has torn from us. As for the first hope,
it corresponds to a natural feeling of the justice of compensation,
which is quite correct subjectively, but has no objective validity
whatever. We make our claim for an indemnity for the unnumbered defects
and sorrows of our earthly existence, without the slightest real
prospect or guarantee of receiving it. We long for an eternal life in
which we shall meet no sadness and no pain, but an unbounded peace
and joy. The pictures that most men form of this blissful existence
are extremely curious; the immaterial soul is placed in the midst of
grossly material pleasures. The imagination of each believer paints
the enduring splendor according to his personal taste. The American
Indian, whose athanatism Schiller has so well depicted, trusts to
find in his Paradise the finest hunting-grounds with innumerable
hordes of buffaloes and bears; the Eskimo looks forward to sun-tipped
icebergs with an inexhaustible supply of bears, seals, and other polar
animals; the effeminate Cingalese frames his Paradise on the wonderful
island-paradise of Ceylon with its noble gardens and forests--adding
that there will be unlimited supplies of rice and curry, of cocoanuts
and other fruit, always at hand; the Mohammedan Arab believes it will
be a place of shady gardens of flowers, watered by cool springs, and
filled with lovely maidens; the Catholic fisherman of Sicily looks
forward to a daily superabundance of the most valuable fishes and the
finest macaroni, and eternal absolution for all his sins, which he
can go on committing in his eternal home; the evangelical of North
Europe longs for an immense Gothic cathedral, in which he can chant
the praises of the Lord of Hosts for all eternity. In a word, each
believer really expects his eternal life to be a direct continuation
of his individual life on earth, only in a "much improved and enlarged

We must lay special stress on the thoroughly materialistic character
of _Christian_ athanatism, which is closely connected with the absurd
dogma of the "resurrection of the body." As thousands of paintings of
famous masters inform us, the bodies that have risen again, with the
souls that have been born again, walk about in heaven just as they did
in this vale of tears; they see God with their eyes, they hear His
voice with their ears, they sing hymns to His praise with their larynx,
and so forth. In fine, the modern inhabitants of the Christian Paradise
have the same dual character of body and soul, the same organs of an
earthly body, as our ancient ancestors had in Odin's Hall in Walhalla,
as the "immortal" Turks and Arabs have in Mohammed's lovely gardens, as
the old Greek demi-gods and heroes had in the enjoyment of nectar and
ambrosia at the table of Zeus.

But, however gloriously we may depict this eternal life in Paradise,
it remains _endless_ in duration. Do we realize what "eternity"
means?--the uninterrupted continuance of our individual life forever!
The profound legend of the "wandering Jew," the fruitless search for
rest of the unhappy Ahasuerus, should teach us to appreciate such
an "eternal life" at its true value. The best we can desire after a
courageous life, spent in doing good according to our light, is the
eternal peace of the grave. "Lord, give them an eternal rest."

Any impartial scholar who is acquainted with geological calculations
of time, and has reflected on the long series of millions of years the
organic history of the earth has occupied, must admit that the crude
notion of an eternal life is not a _comfort_, but a fearful _menace_,
to the best of men. Only want of clear judgment and consecutive thought
can dispute it.

The best and most plausible ground for athanatism is found in the
hope that immortality will reunite us to the beloved friends who have
been prematurely taken from us by some grim mischance. But even this
supposed good fortune proves to be an illusion on closer inquiry; and
in any case it would be greatly marred by the prospect of meeting the
less agreeable acquaintances and the enemies who have troubled our
existence here below. Even the closest family ties would involve many
a difficulty. There are plenty of men who would gladly sacrifice all
the glories of Paradise if it meant the eternal companionship of their
"better half" and their mother-in-law. It is more than questionable
whether Henry VIII. would like the prospect of living eternally with
his six wives; or Augustus the Strong of Poland, who had a hundred
mistresses and three hundred and fifty-two children. As he was on good
terms with the Vicar of Christ, he must be assumed to be in Paradise,
in spite of his sins, and in spite of the fact that his mad military
ventures cost the lives of more than a hundred thousand Saxons.

Another insoluble difficulty faces the athanatist when he asks _in what
stage of their individual development_ the disembodied souls will spend
their eternal life. Will the new-born infant develop its psychic powers
in heaven under the same hard conditions of the "struggle for life"
which educate man here on earth? Will the talented youth who has fallen
in the wholesale murder of war unfold his rich, unused mental powers in
Walhalla? Will the feeble, childish old man, who has filled the world
with the fame of his deeds in the ripeness of his age, live forever in
mental decay? Or will he return to an earlier stage of development?
If the immortal souls in Olympus are to live in a condition of
rejuvenescence and perfectness, then both the stimulus to the formation
of, and the interest in, personality disappear for them.

Not less impossible, in the light of pure reason, do we find the
anthropistic myth of the "last judgment," and the separation of the
souls of men into two great groups, of which one is destined for
the eternal joys of Paradise and the other for the eternal torments
of hell--and that from a personal God who is called the "Father of
Love"! And it is this "Universal Father" who has himself created the
conditions of heredity and adaptation, in virtue of which the elect, on
the one side, were _bound_ to pursue the path towards eternal bliss,
and the luckless poor and miserable, on the other hand, were _driven_
into the paths of the damned?

A critical comparison of the countless and manifold fantasies which
belief in immortality has produced during the last few thousand years
in the different races and religions yields a most remarkable picture.
An intensely interesting presentation of it, based on most extensive
original research, may be found in Adalbert Svoboda's distinguished
works, _The Illusion of the Soul_ and _Forms of Faith_. However absurd
and inconsistent with modern knowledge most of these myths seem to be,
they still play an important part, and, as "postulates of practical
reason," they exercise a powerful influence on the opinions of
individuals and on the destiny of races.

The idealist and spiritualist philosophy of the day will freely grant
that these prevalent materialistic forms of belief in immortality are
untenable; it will say that the refined idea of an immaterial soul,
a Platonic "idea" or a transcendental psychic substance, must be
substituted for them. But modern realism can have nothing whatever to
do with these incomprehensible notions; they satisfy neither the mind's
feeling of causality nor the yearning of our emotions. If we take a
comprehensive glance at all that modern anthropology, psychology,
and cosmology teach with regard to athanatism, we are forced to this
definite conclusion: "The belief in the immortality of the human soul
is a dogma which is in hopeless contradiction with the most solid
empirical truths of modern science."



    The Fundamental Chemical Law of the Constancy of Matter--The
    Fundamental Physical Law of the Conservation of Energy--Combination
    of Both Laws in the Law of Substance--The Kinetic, Pyknotic,
    and Dualistic Ideas of Substance--Monism of Matter--Ponderable
    Matter--Atoms and Elements--Affinity of the Elements--The Soul of
    the Atom (Feeling and Inclination)--Existence and Character of
    Ether--Ether and Ponderable Matter--Force and Energy--Potential
    and Actual Force--Unity of Natural Forces--Supremacy of the Law of

The supreme and all-pervading law of nature, the true and only
cosmological law, is, in my opinion, _the law of substance_; its
discovery and establishment is the greatest intellectual triumph of the
nineteenth century, in the sense that all other known laws of nature
are subordinate to it. Under the name of "law of substance" we embrace
two supreme laws of different origin and age--the older is the chemical
law of the "conservation of matter," and the younger is the physical
law of the "conservation of energy."[23] It will be self-evident to
many readers, and it is acknowledged by most of the scientific men of
the day, that these two great laws are essentially inseparable. This
fundamental thesis, however, is still much contested in some quarters,
and we must proceed to furnish the proof of it. But we must first
devote a few words to each of the two laws.

The law of the "_persistence_" or "_indestructibility of matter_,"
established by Lavoisier in 1789, may be formulated thus: The sum of
matter, which fills infinite space, is unchangeable. A body has merely
changed its form, when it seems to have disappeared. When coal burns,
it is changed into carbonic-acid gas by combination with the oxygen of
the atmosphere; when a piece of sugar melts in water, it merely passes
from the solid to the fluid condition. In the same way, it is merely
a question of change of form in the cases where a new body seems to
be produced. A shower of rain is the moisture of the atmosphere cast
down in the form of drops of water; when a piece of iron rusts, the
surface layer of the metal has combined with water and with atmospheric
oxygen, and formed a "rust," or oxyhydrate of iron. Nowhere in nature
do we find an example of the production, or "creation," of new matter;
nowhere does a particle of existing matter pass entirely away. This
empirical truth is now the unquestionable foundation of chemistry; it
may be directly verified at any moment by means of the balance. To the
great French chemist Lavoisier belongs the high merit of first making
this experiment with the balance. At the present day the scientist, who
is occupied from one end of the year to the other with the study of
natural phenomena, is so firmly convinced of the absolute "constancy"
of matter that he is no longer able to imagine the contrary state of

We may formulate the "_law of the persistence of force_" or
"_conservation of energy_" thus: The sum of force, which is at work in
infinite space and produces all phenomena, is unchangeable. When the
locomotive rushes along the line, the potential energy of the steam
is transformed into the kinetic or actual energy of the mechanical
movement; when we hear its shrill whistle, as it speeds along, the
sound-waves of the vibrating atmosphere are conveyed through the
tympanum and the three bones of the ear into the inner labyrinth, and
thence transferred by the auditory nerve to the acoustic ganglionic
cells which form the centre of hearing in the temporal lobe of the
gray bed of the brain. The whole marvellous panorama of life that
spreads over the surface of our globe is, in the last analysis,
transformed sunlight. It is well known how the remarkable progress of
technical science has made it possible for us to convert the different
physical forces from one form to another; heat may be changed into
molar movement, or movement of mass; this in turn into light or sound,
and then into electricity, and so forth. Accurate measurement of
the quantity of force which is used in this metamorphosis has shown
that it is "constant" or unchanged. No particle of living energy is
ever extinguished; no particle is ever created anew. Friedrich Mohr,
of Bonn, was very near to the discovery of this great fact in 1837,
but the discovery was actually made by the able Swabian physician,
Robert Mayer, of Heilbronn, in 1842. Independently of Mayer, however,
the principle was reached almost at the same time by the famous
physiologist, Hermann Helmholtz; five years afterwards he pointed out
its general application to, and fertility in, every branch of physics.
We ought to say to-day that it rules also in the entire province of
physiology--that is, of "organic physics"; but on that point we meet
a strenuous opposition from the vitalistic biologists and the dualist
and spiritualist philosophers. For these the peculiar "spiritual
forces" of human nature are a group of "free" forces, not subject to
the law of energy; the idea is closely connected with the dogma of the
"freedom of the will." We have, however, already seen (p. 204) that the
dogma is untenable. Modern physics draws a distinction between "force"
and "energy," but our general observations so far have not needed a
reference to it.

The conviction that these two great cosmic theorems, the chemical law
of the persistence of matter and the physical law of the persistence
of force, are fundamentally one, is of the utmost importance in our
monistic system. The two theories are just as intimately united as
their objects--matter and force or energy. Indeed, this fundamental
unity of the two laws is self-evident to many monistic scientists and
philosophers, since they merely relate to two different aspects of one
and the same object, the _cosmos_. But, however natural the thought may
be, it is still very far from being generally accepted. It is stoutly
contested by the entire dualistic philosophy, vitalistic biology,
and parallelistic psychology; even, in fact, by a few (inconsistent)
monists, who think they find a check to it in "consciousness," in the
higher mental activity of man, or in other phenomena of our "free
mental life."

For my part, I am convinced of the profound importance of the unifying
"law of substance," as an expression of the inseparable connection in
reality of two laws which are only separated in conception. That they
were not originally taken together and their unity recognized from
the beginning is merely an accident of the date of their respective
discoveries. The earlier and more accessible chemical law of the
persistence of matter was detected by Lavoisier in 1789, and, after
a general application of the balance, became the basis of exact
chemistry. On the other hand, the more recondite law of the persistence
of force was only discovered by Mayer in 1842, and only laid down
as the basis of exact physics by Helmholtz. The unity of the two
laws--still much disputed--is expressed by many scientists who are
convinced of it in the formula: "Law of the persistence of matter and
force." In order to have a briefer and more convenient expression for
this fundamental thought, I proposed some time ago to call it the "law
of substance" or the "fundamental cosmic law"; it might also be called
the "universal law," or the "law of constancy," or the "axiom of the
constancy of the universe." In the ultimate analysis it is found to be
a necessary consequence of the principle of causality.[24]

The first thinker to introduce the purely monistic conception of
substance into science and appreciate its profound importance was the
great philosopher Baruch Spinoza; his chief work appeared shortly after
his premature death in 1677, just one hundred years before Lavoisier
gave empirical proof of the constancy of matter by means of the
chemist's principal instrument, the balance. In his stately pantheistic
system the notion of the _world_ (the universe, or the cosmos) is
identical with the all-pervading notion of God; it is at one and the
same time the purest and most rational _monism_ and the clearest and
most abstract _monotheism_. This universal substance, this "divine
nature of the world," shows us two different aspects of its being, or
two fundamental attributes--matter (infinitely _extended_ substance)
and spirit (the all-embracing energy of _thought_). All the changes
which have since come over the idea of substance are reduced, on a
logical analysis, to this supreme thought of Spinoza's; with Goethe
I take it to be the loftiest, profoundest, and truest thought of all
ages. Every single object in the world which comes within the sphere
of our cognizance, all individual forms of existence, are but special
transitory forms--_accidents_ or _modes_--of substance. These modes are
material things when we regard them under the attribute of _extension_
(or "occupation of space"), but forces or ideas when we consider them
under the attribute of _thought_ (or "energy"). To this profound
thought of Spinoza our purified monism returns after a lapse of two
hundred years; for us, too, matter (space-filling substance) and energy
(moving force) are but two inseparable attributes of the one underlying

Among the various modifications which the fundamental idea of substance
has undergone in modern physics, in association with the prevalent
atomism, we shall select only two of the most divergent theories for
a brief discussion, the kinetic and the pyknotic. Both theories agree
that we have succeeded in reducing all the different forces of nature
to one common original force; gravity and chemical action, electricity
and magnetism, light and heat, etc., are only different manifestations,
forms, or _dynamodes_, of a single primitive force (_prodynamis_).
This fundamental force is generally conceived as a vibratory motion
of the smallest particles of matter--a vibration of atoms. The atoms
themselves, according to the usual "kinetic theory of substance," are
dead, separate particles of matter, which dance to and fro in empty
space and act at a distance. The real founder and most distinguished
representative of the kinetic theory is Newton, the famous discoverer
of the law of gravitation. In his great work, the _Philosophiae
Naturalis Principia Mathematica_ (1687), he showed that throughout the
universe the same law of attraction controls the unvarying constancy of
gravitation; the attraction of two particles being in direct proportion
to their mass and in inverse proportion to the square of their
distance. This universal force of gravity is at work in the fall of
an apple and the tidal wave no less than in the course of the planets
round the sun and the movements of all the heavenly bodies. Newton
had the immortal merit of establishing the law of gravitation and
embodying it in an indisputable mathematical formula. Yet this _dead
mathematical formula_, on which most scientists lay great stress, as so
frequently happens, gives us merely the _quantitative_ demonstration
of the theory; it gives us no insight whatever into the _qualitative_
nature of the phenomena. The action at a distance without a medium,
which Newton deduced from his law of gravitation, and which became one
of the most serious and most dangerous dogmas of later physics, does
not afford the slightest explanation of the real causes of attraction;
indeed, it long obstructed our way to the real discovery of them. I
cannot but suspect that his speculations on this mysterious action at a
distance contributed not a little to the leading of the great English
mathematician into the obscure labyrinth of mystic dreams and theistic
superstition in which he passed the last thirty-four years of his
life; we find him, at the end, giving metaphysical hypotheses on the
predictions of Daniel and on the paradoxical fantasies of St. John.

In fundamental opposition to the theory of vibration, or the kinetic
theory of substance, we have the modern "theory of condensation,"
or the pyknotic theory of substance. It is most ably established
in the suggestive work of J. C. Vogt on _The Nature of Electricity
and Magnetism on the Basis of a Simplified Conception of Substance_
(1891). Vogt assumes the primitive force of the world, the universal
_prodynamis_, to be, not the vibration or oscillation of particles in
empty space, but the condensation of a simple primitive substance,
which fills the infinity of space in an unbroken continuity. Its
sole inherent mechanical form of activity consists in a tendency to
condensation or contraction, which produces infinitesimal centres
of condensation; these may change their degree of thickness, and,
therefore, their volume, but are constant as such. These minute parts
of the universal substance, the centres of condensation, which might
be called _pyknatoms_, correspond in general to the ultimate separate
atoms of the kinetic theory; they differ, however, very considerably in
that they are credited with sensation and inclination (or will-movement
of the simplest form), _with souls_, in a certain sense--in harmony
with the old theory of Empedocles of the "love and hatred of the
elements." Moreover, these "atoms with souls" do not float in empty
space, but in the continuous, extremely attenuated intermediate
substance, which represents the uncondensed portion of the primitive
matter. By means of certain "constellations, centres of perturbation,
or systems of deformation," great masses of centres of condensation
quickly unite in immense proportions, and so obtain a preponderance
over the surrounding masses. By that process the primitive substance,
which in its original state of quiescence had the same mean consistency
throughout, divides or differentiates into two kinds. The centres
of disturbance, which _positively_ exceed the mean consistency in
virtue of the _pyknosis_ or condensation, form the ponderable matter
of bodies; the finer, intermediate substance, which occupies the space
between them, and _negatively_ falls below the mean consistency, forms
the ether, or imponderable matter. As a consequence of this division
into mass and ether there ensues a ceaseless struggle between the two
antagonistic elements, and this struggle is the source of all physical
processes. The positive ponderable matter, the element with the feeling
of like or desire, is continually striving to complete the process of
condensation, and thus collecting an enormous amount of _potential_
energy; the negative, imponderable matter, on the other hand, offers a
perpetual and equal resistance to the further increase of its strain
and of the feeling of dislike connected therewith, and thus gathers the
utmost amount of _actual_ energy.

We cannot go any further here into the details of the brilliant
theory of J. C. Vogt. The interested reader cannot do better than
have recourse to the second volume of the above work for a clear,
popular exposition of the difficult problem. I am myself too little
informed in physics and mathematics to enter into a critical discussion
of its lights and shades; still, I think that this pyknotic theory
of substance will prove more acceptable to every biologist who is
convinced of the unity of nature than the kinetic theory which prevails
in physics to-day. A misunderstanding may easily arise from the fact
that Vogt puts his process of condensation in explicit contradiction
with the general phenomenon of motion; but it must be remembered that
he is speaking of vibratory movement in the sense of the physicist. His
hypothetical "condensation" is just as much determined by a movement
of substance as is the hypothetical "vibration"; only the kind of
movement and the relation of the moving elements are very different in
the two hypotheses. Moreover, it is not the whole theory of vibration,
but only an important section of it, that is contradicted by the theory
of condensation.

Modern physics, for the most part, still firmly adheres to the older
theory of vibration, to the idea of an _actio in distans_ and the
eternal vibration of dead atoms in empty space; it rejects the pyknotic
theory. Although Vogt's theory may be still far from perfect, and his
original speculations may be marred by many errors, yet I think he has
rendered a very good service in eliminating the untenable principles
of the kinetic theory of substance. As to my own opinion--and that of
many other scientists--I must lay down the following theses, which
are involved in Vogt's pyknotic theory, as indispensable for a truly
monistic view of substance, and one that covers the whole field of
organic and inorganic nature:

I. The two fundamental forms of substance, ponderable matter and ether,
are not dead and only moved by extrinsic force, but they are endowed
with sensation and will (though, naturally, of the lowest grade); they
experience an inclination for condensation, a dislike of strain; they
strive after the one and struggle against the other.

II. There is no such thing as empty space; that part of space which is
not occupied with ponderable atoms is filled with ether.

III. There is no such thing as an action at a distance through
perfectly empty space; all action of bodies upon each other is either
determined by immediate contact or is effected by the mediation of

Both the theories of substance which we have just contrasted are
_monistic_ in principle, since the opposition between the two
conditions of substance--mass and ether--is not original; moreover,
they involve a continuous immediate contact and reciprocal action
of the two elements. It is otherwise with the _dualistic_ theories
of substance which still obtain in the idealist and spiritualist
philosophy, and which have the support of a powerful theology, in so
far as theology indulges in such metaphysical speculations. These
theories draw a distinction between two entirely different kinds of
substance, material and immaterial. Material substance enters into
the composition of the bodies which are the object of physics and
chemistry; the law of the persistence of matter and force is confined
to this world (apart from a belief in its "creation from nothing"
and other miracles). Immaterial substance is found in the "spiritual
world" to which the law does not extend; in this province the laws
of physics and chemistry are either entirely inapplicable or they
are subordinated to a "vital force," or a "free will," or a "divine
omnipotence," or some other phantom which is beyond the ken of critical
science. In truth, these profound errors need no further refutation
to-day, for experience has never yet discovered for us a single
immaterial substance, a single force which is not dependent on matter,
or a single form of energy which is not exerted by material movement,
whether it be of mass, or of ether, or of both. Even the most elaborate
and most perfect forms of energy that we know--the psychic life of
the higher animals, the thought and reason of man--depend on material
processes, or changes in the neuroplasm of the ganglionic cells; they
are inconceivable apart from such modifications. I have already shown
(chap. xi.) that the physiological hypothesis of a special, immaterial
"soul-substance" is untenable.

The study of ponderable matter is primarily the concern of chemistry.
Few are ignorant of the astonishing theoretical progress which this
science has made in the course of the century and the immense practical
influence it has had on every aspect of modern life. We shall confine
ourselves here to a few remarks on the more important questions
which concern the nature of ponderable matter. It is well known that
analytical chemistry has succeeded in resolving the immense variety
of bodies in nature into a small number of simple elements--that is,
simple bodies which are incapable of further analysis. The number of
these elements is about seventy. Only fourteen of them are widely
distributed on the earth and of much practical importance; the majority
are rare elements (principally metals) of little practical moment. The
affinity of these groups of elements, and the remarkable proportions of
their atomic weights, which Lothar Meyer and Mendelejeff have proved
in their _Periodic System of the Elements_, make it extremely probable
that they are not _absolute species_ of ponderable matter--that is,
not eternally unchangeable particles. The seventy elements have in
that system been distributed into eight leading groups, and arranged
in them according to their atomic weight, so that the elements which
have a chemical affinity are formed into families. The relations of
the various groups in such a natural system of the elements recall,
on the one hand, similar relations of the innumerable compounds of
carbon, and, again, the relations of parallel groups in the natural
arrangement of the animal and plant species. Since in the latter
cases the "affinity" of the related forms is based on descent from a
common parent form, it seems very probable that the same holds good of
the families and orders of the chemical elements. We may, therefore,
conclude that the "empirical elements" we now know are not really
simple, ultimate, and unchangeable forms of matter, but compounds
of homogeneous, simple, primitive atoms, variously distributed as
to number and grouping. The recent speculations of Gustav Wendt,
Wilhelm Preyer, Sir W. Crookes, and others, have pointed out how we
may conceive the evolution of the elements from a simple primitive
material, the _prothyl_.

The modern atomistic theory, which is regarded as an indispensable
instrument in chemistry to-day, must be carefully distinguished from
the old philosophic atomism which was taught more than two thousand
years ago by a group of distinguished thinkers of antiquity--Leucippus,
Democritus, and Epicurus: it was considerably developed and modified
later on by Descartes, Hobbes, Leibnitz, and other famous philosophers.
But it was not until 1808 that modern atomism assumed a definite and
acceptable form, and was furnished with an empirical basis by Dalton,
who formulated the "law of simple and multiple proportions" in the
formation of chemical combinations. He first determined the atomic
weight of the different elements, and thus created the solid and exact
foundation on which more recent chemical theories are based; these
are all _atomistic_, in the sense that they assume the elements to be
made up of homogeneous, infinitesimal, distinct particles, which are
incapable of further analysis. That does not touch the question of the
real nature of the atoms--their form, size, psychology, etc. These
atomic qualities are merely hypothetical; while the _chemistry_ of the
atoms, their "chemical affinity"--that is, the constant proportion in
which they combine with the atoms of other elements--is empirical.[25]

The different relation of the various elements towards each other,
which chemistry calls "affinity," is one of the most important
properties of ponderable matter; it is manifested in the different
relative quantities or proportions of their combination in the
intensity of its consummation. Every shade of inclination, from
complete indifference to the fiercest passion, is exemplified in the
chemical relation of the various elements towards each other, just
as we find in the psychology of man, and especially in the life of
the sexes. Goethe, in his classical romance, _Affinities_, compared
the relations of pairs of lovers with the phenomenon of the same name
in the formation of chemical combinations. The irresistible passion
that draws Edward to the sympathetic Ottilia, or Paris to Helen, and
leaps over all bounds of reason and morality, is the same powerful
"unconscious" attractive force which impels the living spermatozoon to
force an entrance into the ovum in the fertilization of the egg of the
animal or plant--the same impetuous movement which unites two atoms
of hydrogen to one atom of oxygen for the formation of a molecule of
water. This fundamental _unity of affinity in the whole of nature_,
from the simplest chemical process to the most complicated love story,
was recognized by the great Greek scientist, Empedocles, in the fifth
century B.C., in his theory of "the love and hatred of the elements."
It receives empirical confirmation from the interesting progress of
cellular psychology, the great significance of which we have only
learned to appreciate in the last thirty years. On those phenomena we
base our conviction that even the _atom_ is not without a rudimentary
form of sensation and will, or as it is better expressed, of feeling
(_aesthesis_) and inclination (_tropesis_)--that is, a universal "soul"
of the simplest character. The same must be said of the molecules which
are composed of two or more atoms. Further combinations of different
kinds of these molecules give rise to simple and, subsequently, complex
chemical compounds, in the activity of which the same phenomena are
repeated in a more complicated form.

The study of ether, or imponderable matter, pertains principally to
physics. The existence of an extremely attenuated medium, filling the
whole of space outside of ponderable matter, was known and applied
to the elucidation of various phenomena (especially light) a long
time ago; but it was not until the second half of the nineteenth
century that we became more closely acquainted with this remarkable
substance, in connection with our astonishing empirical discoveries in
the province of electricity, with their experimental detection, their
theoretical interpretation, and their practical application. The path
was opened in particular by the famous researches of Heinrich Hertz, of
Bonn, in 1888. The premature death of a brilliant young physicist of so
much promise cannot be sufficiently deplored. Like the premature death
of Spinoza, Raphael, Schubert, and many other great men, it is one of
those brutal facts of human history which are enough of themselves to
destroy the untenable myth of a "wise Providence" and an "All-loving
Father in heaven."

The existence of ether (or cosmic ether) as a real element is a
_positive fact_, and has been known as such for the last twelve years.
We sometimes read even to-day that ether is a "pure hypothesis";
this erroneous assertion comes not only from uninformed philosophers
and "popular" writers, but even from certain "prudent and exact
physicists." But there would be just as much reason to deny the
existence of ponderable matter. As a matter of fact, there are
metaphysicians who accomplish even this feat, and whose highest wisdom
lies in denying or calling into question the existence of an external
universe; according to them only one real entity exists--their own
precious personality, or, to be more correct, their immortal soul.
Several modern physiologists have embraced this ultra-idealist view,
which is to be found in Descartes, Berkeley, Fichte, and others.
Their "psycho-monism" affirms: "One thing only exists, and that is
my own mind." This audacious spiritualism seems to us to rest on an
erroneous inference from Kant's correct critical theory, that we can
know the outer world only in the phenomenal aspect which is accessible
to our human organs of thought--the brain and the organs of sense. If
by those means we can attain only an imperfect and limited knowledge
of the material world, that is no reason for denying its existence
altogether. In my opinion, the existence of ether is as certain as that
of ponderable matter--as certain as my own existence, as I reflect and
write on it. As we assure ourselves of the existence of ponderable
matter by its mass and weight, by chemical and mechanical experiments,
so we prove that of ether by the experiences and experiments of optics
and electricity.

Although, however, the existence of ether is now regarded as a
positive fact by nearly all physicists, and although many effects of
this remarkable substance are familiar to us through an extensive
experience, especially in the way of optical and electrical experiments,
yet we are still far from being clear and confident as to its real
character. The views of the most eminent physicists, who have made
a special study of it, are extremely divergent; they frequently
contradict each other on the most important points. One is, therefore,
free to choose among the contradictory hypotheses according to one's
knowledge and judgment. I will put in the following eight theses the
view which has approved itself to me after mature reflection on the
subject, though I am no expert in this department:

I. Ether fills the whole of space, in so far as it is not occupied by
ponderable matter, as a _continuous substance_; it fully occupies the
space between the atoms of ponderable matter.

II. Ether has probably no chemical quality, and is not composed of
atoms. If it be supposed that it consists of minute homogeneous atoms
(for instance, indivisible etheric particles of a uniform size), it
must be further supposed that there is something else between these
atoms, either "empty space" or a third, completely unknown medium, a
purely hypothetical "interether"; the question as to the nature of this
brings us back to the original difficulty, and so on _in infinitum_.

III. As the idea of an empty space and an action at a distance is
scarcely possible in the present condition of our knowledge (at least
it does not help to a clear monistic view), I postulate for ether a
special structure which is not atomistic, like that of ponderable
matter, and which may provisionally be called (without further
determination) _etheric_ or _dynamic_ structure.

IV. The consistency of ether is also peculiar, on our hypothesis, and
different from that of ponderable matter. It is neither gaseous, as
some conceive, nor solid, as others suppose; the best idea of it can be
formed by comparison with an extremely attenuated, elastic, and light

V. Ether may be called _imponderable_ matter in the sense that we
have no means of determining its weight experimentally. If it really
has weight, as is very probable, it must be so slight as to be far
below the capacity of our most delicate balance. Some physicists have
attempted to determine its weight by the energy of the light-waves, and
have discovered that it is some fifteen trillion times lighter than
atmospheric air; on that hypothesis a sphere of ether of the size of
our earth would weigh at least two hundred and fifty pounds(?).

VI. The etheric consistency may probably (in accordance with the
pyknotic theory) pass into the gaseous state under certain conditions
by progressive condensation, just as a gas may be converted into a
fluid, and ultimately into a solid, by lowering its temperature.

VII. Consequently, these three conditions of matter may be arranged
(and it is a point of great importance in our monistic cosmogony) in a
genetic, continuous order. We may distinguish five stages in it: (1)
the etheric, (2) the gaseous, (3) the fluid, (4) the viscous (in the
living protoplasm), and (5) the solid state.

VIII. Ether is boundless and immeasurable, like the space it occupies.
It is in eternal motion; and this specific movement of ether (it is
immaterial whether we conceive it as vibration, strain, condensation,
etc.), in reciprocal action with mass-movement (or gravitation), is the
ultimate cause of all phenomena.

"The great question of the nature of ether," as Hertz justly calls
it, includes the question of its relation to ponderable matter; for
these two forms of matter are not only always in the closest external
contact, but also in eternal, dynamic, reciprocal action. We may divide
the most general phenomena of nature, which are distinguished by
physics as natural forces or "functions of matter," into two groups;
the first of them may be regarded mainly (though not exclusively) as a
function of ether, and the second a function of ponderable matter--as
in the following scheme which I take from my _Monism_:


  ETHER--Imponderable.            | MASS--Ponderable.
 1. _Consistency_:                | 1. _Consistency_:
 Etheric (_i.e._, neither         | Not etheric (but gaseous, fluid,
 gaseous nor fluid, nor solid).   | or solid).
 2. _Structure_:                  | 2. _Structure_:
 Not atomistic, not made up of    | Atomistic, made up of infinitesimal,
 separate particles (atoms), but  | distinct particles (atoms)
 continuous.                      | discontinuous.
 3. _Chief Functions_:            | 3. _Chief Functions_:
 Light, radiant heat, electricity,| Gravity, inertia, molecular heat,
 and magnetism.                   | and chemical affinity.

The two groups of functions of matter, which we have opposed in this
table, may, to some extent, be regarded as the outcome of the first
"division of labor" in the development of matter, the "primary ergonomy
of matter." But this distinction must not be supposed to involve an
absolute separation of the two antithetic groups; they always retain
their connection, and are in constant reciprocal action. It is well
known that the optical and electrical phenomena of ether are closely
connected with mechanical and chemical changes in ponderable elements;
the radiant heat of ether may be directly converted into the mechanical
heat of the mass; gravitation is impossible unless the ether effects
the mutual attraction of the separated atoms, because we cannot admit
the idea of an _actio in distans_. In like manner, the conversion
of one form of energy into another, as indicated in the law of the
persistence of force, illustrates the constant reciprocity of the two
chief types of substance, ether and mass.

The great law of nature, which, under the title of the "law of
substance," we put at the head of all physical considerations, was
conceived as the law of "the persistence of force" by Robert Meyer, who
first formulated it, and Helmholtz, who continued the work. Another
German scientist, Friedrich Mohr, of Bonn, had clearly outlined it in
its main features ten years earlier (1837). The old idea of _force_
was, after a time, differentiated by modern physics from that of
_energy_, which was at first synonymous with it. Hence the law is
now usually called the "law of the persistence of energy." However,
this finer distinction need not enter into the general consideration,
to which I must confine myself here, and into the question of the
great principle of the "persistence of substance." The interested
reader will find a very clear treatment of the question in Tyndall's
excellent paper on "The Fundamental Law of Nature," in his _Fragments
of Science_. It fully explains the broad significance of this profound
cosmic law, and points out its application to the main problems of
very different branches of science. We shall confine our attention to
the important fact that the "principle of energy" and the correlative
idea of the unity of natural forces, on the basis of a common origin,
are now accepted by all competent physicists, and are regarded as the
greatest advance of physics in the nineteenth century. We now know that
heat, sound, light, chemical action, electricity, and magnetism are all
modes of motion. We can, by a certain apparatus, convert any one of
these forces into another, and prove by an accurate measurement that
not a single particle of energy is lost in the process.

The sum-total of force or energy in the universe remains constant, no
matter what changes take place around us; it is eternal and infinite,
like the matter on which it is inseparably dependent. The whole drama
of nature apparently consists in an alternation of movement and
repose; yet the bodies at rest have an inalienable quantity of force,
just as truly as those that are in motion. It is in this movement
that the potential energy of the former is converted into the kinetic
energy of the latter. "As the principle of the persistence of force
takes into account repulsion as well as attraction, it affirms that
the mechanical value of the potential energy and the kinetic energy
in the material world is a constant quantity. To put it briefly, the
force of the universe is divided into two parts, which may be mutually
converted, according to a fixed relation of value. The diminution of
the one involves the increase of the other; the total value remains
unchanged in the universe." The potential energy and the actual, or
kinetic, energy are being continually transformed from one condition to
the other; but the infinite sum of force in the world at large never
suffers the slightest curtailment.

Once modern physics had established the law of substance as far as
the simpler relations of inorganic bodies are concerned, physiology
took up the story, and proved its application to the entire province
of the organic world. It showed that all the vital activities of the
organism--without exception--are based on a constant "reciprocity
of force" and a correlative change of material, or metabolism, just
as much as the simplest processes in "lifeless" bodies. Not only
the growth and the nutrition of plants and animals, but even their
functions of sensation and movement, their sense-action and psychic
life, depend on the conversion of potential into kinetic energy,
and _vice versâ_. This supreme law dominates also those elaborate
performances of the nervous system which we call, in the higher animals
and man, "the action of the mind."

Our monistic view, that the great cosmic law applies throughout the
whole of nature, is of the highest moment. For it not only involves,
on its positive side, the essential unity of the cosmos and the
causal connection of all phenomena that come within our cognizance,
but it also, in a negative way, marks the highest intellectual
progress, in that it definitely rules out the three central dogmas of
metaphysics--God, freedom, and immortality. In assigning mechanical
causes to phenomena everywhere, the law of substance comes into line
with the universal law of causality.



    The Notion of Creation--Miracles--Creation of the Whole Universe
    and of its Various Parts--Creation of Substance (Cosmological
    Creation)--Deism: One Creative Day--Creation of Separate
    Entities--Five Forms of Ontological Creationism--Theory of
    Evolution--I. Monistic Cosmogony--Beginning and End of the
    World--The Infinity and Eternity of the Universe--Space and
    Time--_Universum perpetuum mobile_--Entropy of the Universe--II.
    Monistic Geogeny--History of the Inorganic and Organic Worlds--III.
    Monistic Biogeny--Transformism and the Theory of Descent: Lamarck
    and Darwin--IV. Monistic Anthropogeny--Origin of Man

The greatest, vastest, and most difficult of all cosmic problems is
that of the origin and development of the world--the "question of
creation," in a word. Even to the solution of this most difficult
world-riddle the nineteenth century has contributed more than all its
predecessors; in a certain sense, indeed, it has found the solution. We
have at least attained to a clear view of the fact that all the partial
questions of creation are indivisibly connected, that they represent
one single, comprehensive "cosmic problem," and that the key to this
problem is found in the one magic word--evolution. The great questions
of the creation of man, the creation of the animals and plants, the
creation of the earth and the sun, etc., are all parts of the general
question, What is the origin of the whole world? Has it been _created_
by supernatural power, or has it been _evolved_ by a natural process?
What are the causes and the manner of this evolution? If we succeed
in finding the correct answer to one of these questions, we have,
according to our monistic conception of the world, cast a brilliant
light on the solution of them all, and on the entire cosmic problem.

The current opinion as to the origin of the world in earlier ages was
almost a universal belief in creation. This belief has been expressed
in thousands of interesting, more or less fabulous, legends, poems,
cosmogonies, and myths. A few great philosophers were devoid of it,
especially those remarkable free-thinkers of classical antiquity who
first conceived the idea of natural evolution. All the creation-myths,
on the contrary, were of a supernatural, miraculous, and transcendental
character. Incompetent, as it was, to investigate for itself the
nature of the world and its origin by natural causes, the undeveloped
mind naturally had recourse to the idea of miracle. In most of these
creation-myths _anthropism_ was blended with the belief in the
miraculous. The creator was supposed to have constructed the world on a
definite plan, just as man accomplishes his artificial constructions;
the conception of the creator was generally completely anthropomorphic,
a palpable "anthropistic creationism." The "all-mighty maker of heaven
and earth," as he is called in Genesis and the Catechism, is just as
humanly conceived as the modern creator of Agassiz and Reinke, or the
intelligent "engineer" of other recent biologists.

Entering more fully into the notion of creation, we can distinguish
as two entirely different acts the production of the universe as a
whole and the partial production of its various parts, in harmony with
Spinoza's idea of _substance_ (the universe) and _accidents_ (or
_modes_, the individual phenomena of substance). This distinction is of
great importance, because there are many eminent philosophers who admit
the one and reject the other.

According to this creationist theory, then, God has "made the world
out of nothing." It is supposed that God (a rational, but immaterial,
being) existed by himself for an eternity before he resolved to create
the world. Some supporters of the theory restrict God's creative
function to one single act; they believe that this extramundane God
(the rest of whose life is shrouded in mystery) created the substance
of the world in a single moment, endowed it with the faculty of
the most extensive evolution, and troubled no further about it.
This view may be found, for instance, in the English Deists in many
forms. It approaches very close to our monistic theory of evolution,
only abandoning it in the one instant in which God accomplished the
creation. Other creationists contend that God did not confine himself
to the mere creation of matter, but that he continues to be operative
as the "sustainer and ruler of the world." Different modifications of
this belief are found, some approaching very close to _pantheism_ and
others to complete _theism_. All these and similar forms of belief in
creation are incompatible with the law of the persistence of matter and
force; that law knows nothing of a beginning.

It is interesting to note that E. du Bois-Reymond has identified
himself with this cosmological creationism in his latest speech
(on "Neovitalism," 1894). "It is more consonant with the divine
omnipotence," he says, "to assume that it created the whole material
of the world in one creative act unthinkable ages ago in such
wise that it should be endowed with inviolable laws to control the
origin and the progress of living things--that, for instance, here
on earth rudimentary organisms should arise from which, without
further assistance, the whole of living nature could be evolved, from
a primitive bacillus to the graceful palm-wood, from a primitive
micrococcus to Solomon's lovely wives or to the brain of Newton.
Thus we are content with _one_ creative day, and we derive organic
nature mechanically, without the aid of either old or new vitalism."
Du Bois-Reymond here shows, as in the question of consciousness, the
shallow and illogical character of his monistic thought.

According to another still prevalent theory, which may be called
"ontological creationism," God not only created the world at large,
but also its separate contents. In the Christian world the old Semitic
legend of creation, taken from Genesis, is still very widely accepted;
even among modern scientists it finds an adherent here and there. I
have fully entered into the criticism of it in the first chapter of my
_Natural History of Creation_. The following theories may be enumerated
as the most interesting modifications of this ontological creationism:

I. _Dualistic creation._--God restricted his interference to _two_
creative acts. First he created the inorganic world, mere dead
substance, to which alone the law of energy applies, working blindly
and aimlessly in the mechanism of material things and the building of
the mountains; then God attained intelligence and communicated it to
the purposive intelligent forces which initiate and control organic

II. _Trialistic creation._--God made the world in _three_ creative
acts: (_a_) the creation of the heavens--the extra-terrestrial world,
(_b_) the creation of the earth (as the centre of the world) and of
its living inhabitants, and (_c_) the creation of man (in the image
and likeness of God). This dogma is still widely prevalent among
theologians and other "educated" people; it is taught as the truth in
many of our schools.

III. _Heptameral creation_; a creation in seven days (_teste_
Moses).--Although few educated people really believe in this Mosaic
myth now, it is still firmly impressed on our children in the biblical
lessons of their earliest years. The numerous attempts that have been
made, especially in England, to harmonize it with the modern theory of
evolution have entirely failed. It obtained some importance in science
when Linné adopted it in the establishment of his system, and based his
definition of organic species (which he considered to be unchangeable)
on it: "There are as many different species of animals and plants as
there were different forms created in the beginning by the Infinite."
This dogma was pretty generally held until the time of Darwin (1859),
although Lamarck had already proved its untenability in 1809.

IV. _Periodic creation._--At the beginning of each period of the
earth's history the whole population of animals and plants was created
anew, and destroyed by a general catastrophe at its close; there were
as many general creative acts as there are distinct geological periods
(the catastrophic theory of Cuvier [1818] and Louis Agassiz [1858]).
Palæontology, which seemed to support this theory in its more imperfect
stage, has since completely refuted it.

V. _Individual creation._--Every single man--and every individual
animal and plant--does not arise by a natural process of growth, but
is created by the favor of God. This view of creation is still often
met with in journals, especially in the "births" column. The special
talents and features of our children are often gratefully acknowledged
to be "gifts of God"; their hereditary defects fit into another theory.

The error of these creation-legends and the cognate belief in miracles
must have been apparent to thoughtful minds at an early period; more
than two thousand years ago we find that many attempts were made
to replace them by a rational theory, and to explain the origin of
the world by natural causes. In the front rank, once more, we must
place the leaders of the Ionic school, with Democritus, Heraclitus,
Empedocles, Aristotle, Lucretius, and other ancient philosophers. The
first imperfect attempts which they made astonish us, in a measure,
by the flashes of mental light in which they anticipate modern ideas.
It must be remembered that classical antiquity had not that solid
groundwork for scientific speculation which has been provided by the
countless observations and experiments of modern scientists. During the
Middle Ages--especially during the domination of the papacy--scientific
work in this direction entirely ceased. The torture and the stake of
the Inquisition insured that an unconditional belief in the Hebrew
mythology should be the final answer to all the questions of creation.
Even the phenomena which led directly to the observation of the _facts_
of evolution--the embryology of the plant and the animal, and of
man--remained unnoticed, or only excited the interest of an occasional
keen observer; but their discoveries were ignored or forgotten.
Moreover, the path to a correct knowledge of natural development was
barred by the dominant theory of preformation, the dogma which held
that the characteristic form and structure of each animal and plant
were already sketched in miniature in the germ (cf. p. 54).

The science which we now call the science of evolution (in the broadest
sense) is, both in its general outline and in its separate parts,
a child of the nineteenth century; it is one of its most momentous
and most brilliant achievements. Almost unknown in the preceding
century, this theory has now become the sure foundation of our whole
world-system. I have treated it exhaustively in my _General Morphology_
(1866), more popularly in my _Natural History of Creation_ (1868), and
in its special application to man in my _Anthropogeny_ (1874). Here I
shall restrict myself to a brief survey of the chief advances which
the science has made in the course of the century. It falls into four
sections, according to the nature of its object; that is, it deals with
the natural origin of (1) the cosmos, (2) the earth, (3) terrestrial
forms of life, and (4) man.


The first attempt to explain the constitution and the mechanical
origin of the world in a simple manner by "Newtonian laws"--that is,
by mathematical and physical laws--was made by Immanuel Kant in the
famous work of his youth (1755), _General History of the Earth and
Theory of the Heavens_. Unfortunately, this distinguished and daring
work remained almost unknown for ninety years; it was only disinterred
in 1845 by Alexander Humboldt in the first volume of his _Cosmos_. In
the mean time the great French mathematician, Pierre Laplace, had
arrived independently at similar views to those of Kant, and he gave
them a mathematical foundation in his _Exposition du Système du Monde_
(1796). His chief work, the _Mécanique Céleste_, appeared a hundred
years ago. The analogous features of the cosmogony of Kant and Laplace
consist, as is well known, in a mechanical explanation of the movements
of the planets, and the conclusion which is drawn therefrom, that all
the cosmic bodies were formed originally by a condensation of rotating
nebulous spheres. This "nebular hypothesis" has been much improved
and supplemented since, but it is still the best of all the attempts
to explain the origin of the world on monistic and mechanical lines.
It has recently been strongly confirmed and enlarged by the theory
that this cosmogonic process did not simply take place once, but is
periodically repeated. While new cosmic bodies arise and develop out
of rotating masses of nebula in some parts of the universe, in other
parts old, extinct, frigid suns come into collision, and are once more
reduced by the heat generated to the condition of nebulæ.

Nearly all the older and the more recent cosmogonies, including most
of those which were inspired by Kant and Laplace, started from the
popular idea that the world had had a beginning. Hence, according to
a widespread version of the nebular hypothesis, "in the beginning"
was made a vast nebula of infinitely attenuated and light material,
and at a certain moment ("countless ages ago") a movement of rotation
was imparted to this mass. Given this "first beginning" of the
cosmogonic movement, it is easy, on mechanical principles, to deduce
and mathematically establish the further phenomena of the formation of
the cosmic bodies, the separation of the planets, and so forth. This
first "origin of movement" is Du Bois-Reymond's second "world-enigma";
he regards it as transcendental. Many other scientists and philosophers
are equally helpless before this difficulty; they resign themselves to
the notion that we have here a primary "supernatural impetus" to the
scheme of things, a "miracle."

In our opinion, this second "world-enigma" is solved by the recognition
that movement is as innate and original a property of substance as
is sensation. The proof of this monistic assumption is found, first,
in the law of substance, and, secondly, in the discoveries which
astronomy and physics have made in the latter half of the century. By
the spectral analysis of Bunsen and Kirchhoff (1860) we have found, not
only that the millions of bodies, which fill the infinity of space, are
of the same material as our own sun and earth, but also that they are
in various stages of evolution; we have obtained by its aid information
as to the movements and distances of the stars, which the telescope
would never have given us. Moreover, the telescope itself has been
vastly improved, and has, in alliance with photography, made a host
of scientific discoveries of which no one dreamed at the beginning
of the century. In particular, a closer acquaintance with comets,
meteorites, star-clusters, and nebulæ has helped us to realize the
great significance of the smaller bodies which are found in millions in
the space between the stars.

We now know that the _paths_ of the millions of heavenly bodies are
_changeable_, and to some extent irregular, whereas the planetary
system was formerly thought to be constant, and the rotating spheres
were described as pursuing their orbits in eternal regularity.
Astro-physics owes much of its triumph to the immense progress of other
branches of physics, of optics, and electricity, and especially of
the theory of ether. And here, again, our supreme law of substance is
found to be one of the most valuable achievements of modern science.
We now know that it rules unconditionally in the most distant reaches
of space, just as it does in our planetary system, in the most minute
particle of the earth as well as in the smallest cell of our human
frame. We are, moreover, justified in concluding, if we are not
logically compelled to conclude, that the persistence of matter and
force has held good throughout all time as it does to-day. Through all
eternity the infinite universe has been, and is, subject to the law of

From this great progress of astronomy and physics, which mutually
elucidate and supplement each other, we draw a series of most important
conclusions with regard to the constitution and evolution of the
cosmos, and the persistence and transformation of substance. Let us put
them briefly in the following theses:

I. The _extent_ of the universe is infinite and unbounded; it is empty
in no part, but everywhere filled with substance.

II. The _duration_ of the world is equally infinite and unbounded; it
has no beginning and no end: it is eternity.

III. Substance is everywhere and always in uninterrupted movement and
transformation: nowhere is there perfect repose and rigidity; yet the
infinite quantity of matter and of eternally changing force remains

IV. This universal movement of substance in space takes the form of an
eternal cycle or of a periodical process of evolution.

V. The phases of this evolution consist in a periodic change of
consistency, of which the first outcome is the primary division into
mass and ether--the ergonomy of ponderable and imponderable matter.

VI. This division is effected by a progressive condensation of matter
as the formation of countless infinitesimal "centres of condensation,"
in which the inherent primitive properties of substance--feeling and
inclination--are the active causes.

VII. While minute and then larger bodies are being formed by this
pyknotic process in one part of space, and the intermediate ether
increases its strain, the opposite process--the destruction of cosmic
bodies by collision--is taking place in another quarter.

VIII. The immense quantity of heat which is generated in this
mechanical process of the collision of swiftly moving bodies represents
the new kinetic energy which effects the movement of the resultant
nebulæ and the construction of new rotating bodies. The eternal drama
begins afresh. Even our mother earth, which was formed of part of the
gyrating solar system millions of ages ago, will grow cold and lifeless
after the lapse of further millions, and, gradually narrowing its
orbit, will fall eventually into the sun.

It seems to me that these modern discoveries as to the periodic decay
and re-birth of cosmic bodies, which we owe to the most recent advance
of physics and astronomy, associated with the law of substance, are
especially important in giving us a clear insight into the universal
cosmic process of evolution. In their light our earth shrinks into the
slender proportions of a "mote in the sunbeam," of which unnumbered
millions chase each other through the vast depths of space. Our own
"human nature," which exalted itself into an image of God in its
anthropistic illusion, sinks to the level of a placental mammal, which
has no more value for the universe at large than the ant, the fly of
a summer's day, the microscopic infusorium, or the smallest bacillus.
Humanity is but a transitory phase of the evolution of an eternal
substance, a particular phenomenal form of matter and energy, the true
proportion of which we soon perceive when we set it on the background
of infinite space and eternal time.

Since Kant explained space and time to be merely "forms of
perception"--space the form of external, time of internal,
sensitivity--there has been a keen controversy, which still continues,
over this important problem. A large section of modern metaphysicians
have persuaded themselves that this "critical fact" possesses a great
importance as the starting-point of "a purely idealist theory of
knowledge," and that, consequently, the natural opinion of the ordinary
healthy mind as to the _reality_ of time and space is swept aside. This
narrow and ultra-idealist conception of time and space has become a
prolific source of error. It overlooks the fact that Kant only touched
one side of the problem, the _subjective_ side, in that theory, and
recognized the equal validity of its _objective_ side. "Time and
space," he said, "have empirical reality, but transcendental ideality."
Our modern monism is quite compatible with this thesis of Kant's,
but not with the one-sided exaggeration of the subjective aspect of
the problem; the latter leads logically to the absurd idealism that
culminates in Berkeley's thesis, "Bodies are but ideas; their essence
is in their perception." The thesis should be read thus: "Bodies are
only ideas for my personal consciousness; their existence is just
as real as that of my organs of thought, the ganglionic cells in
the gray bed of my brain, which receive the impress of bodies on my
sense-organs and form those ideas by association of the impressions." It
is just as easy to doubt or to deny the reality of my own consciousness
as to doubt that of time and space. In the delirium of fever, in
hallucinations, in dreams, and in double-consciousness, I take ideas
to be true which are merely fancies. I mistake my own personality for
another (_vide_ p. 185); Descartes' famous _Cogito ergo sum_ applies no
longer. On the other hand, the reality of time and space is now fully
established by that expansion of our philosophy which we owe to the
law of substance and to our monistic cosmogony. When we have happily
got rid of the untenable idea of "empty space," there remains as the
infinite "space-filling"-medium matter, in its two forms of ether and
mass. So also we find a "time-filling" event in the eternal movement,
or genetic energy, which reveals itself in the uninterrupted evolution
of substance, in the _perpetuum mobile_ of the universe.

As a body which has been set in motion continues to move as long as no
external agency interferes with it, the idea was conceived long ago of
constructing an apparatus which should illustrate perpetual motion. The
fact was overlooked that every movement meets with external impediments
and gradually ceases, unless a new impetus is given to it from without
and a new force is introduced to counteract the impediments. Thus, for
instance, a pendulum would swing backward and forward for an eternity
at the same speed if the resistance of the atmosphere and the friction
at the point it hangs from did not gradually deprive it of the
mechanical kinetic energy of its motion and convert it into heat. We
have to furnish it with fresh mechanical energy by a spring (or, as in
the pendulum-clock, by the drag of a weight). Hence it is impossible to
construct a machine that would produce, without external aid, a surplus
of energy by which it could keep itself going. Every attempt to make
such a _perpetuum mobile_ must necessarily fail; the discovery of the
law of substance showed, in addition, the theoretical impossibility of

The case is different, however, when we turn to the world at large, the
boundless universe that is in eternal movement. The infinite matter,
which fills it objectively, is what we call _space_ in our subjective
impression of it; _time_ is our subjective conception of its eternal
movement, which is, objectively, a periodic, cyclic evolution. These
two "forms of perception" teach us the infinity and eternity of the
universe. That is, moreover, equal to saying that the universe itself
is a _perpetuum mobile_. This infinite and eternal "machine of the
universe" sustains itself in eternal and uninterrupted movement,
because every impediment is compensated by an "equivalence of energy,"
and the unlimited sum of kinetic and potential energy remains always
the same. The law of the persistence of force proves also that the idea
of a _perpetuum mobile_ is just as applicable to, and as significant
for, the cosmos as a whole as it is impossible for the isolated action
of any part of it. Hence the theory of _entropy_ is likewise untenable.

The able founder of the mechanical theory of heat (1850), Clausius,
embodied the momentous contents of this important theory in two theses.
The first runs: "The energy of the universe is constant"--that is
one-half of our law of substance, the principle of energy (_vide_ p.
230). The second thesis is: "The energy of the universe tends towards
a maximum." In my opinion this second assertion is just as erroneous
as the first is true. In the theory of Clausius the entire energy of
the universe is of two kinds, one of which (heat of the higher degree,
mechanical, electrical, chemical energy, etc.) is partly convertible
into work, but the other is not; the latter energy, already converted
into heat and distributed in the cooler masses, is irrevocably lost as
far as any further work is concerned. Clausius calls this unconsumed
energy, which is no longer available for mechanical work, _entropy_
(that is, force that is directed _inward_); it is continually
increasing at the cost of the other half. As, therefore, the mechanical
energy of the universe is daily being transformed into heat, and this
cannot be reconverted into mechanical force, the sum of heat and energy
in the universe must continually tend to be reduced and dissipated. All
difference of temperature must ultimately disappear, and the completely
latent heat must be equally distributed through one inert mass of
motionless matter. All organic life and movement must cease when this
maximum of _entropy_ has been reached. That would be a real "end of the

If this theory of entropy were true, we should have a "beginning"
corresponding to this assumed "end" of the world--a minimum of
entropy, in which the differences in temperature of the various parts
of the cosmos would be at a maximum. Both ideas are quite untenable
in the light of our monistic and consistent theory of the eternal
cosmogenetic process; both contradict the law of substance. There is
neither beginning nor end of the world. The universe is infinite, and
eternally in motion; the conversion of kinetic into potential energy,
and _vicissim_, goes on uninterruptedly; and the sum of this actual and
potential energy remains constant. The second thesis of the mechanical
theory of heat contradicts the first, and so must be rejected.

The representatives of the theory of entropy are quite correct as long
as they confine themselves to distinct processes, in which, _under
certain conditions_, the latent heat cannot be reconverted into work.
Thus, for instance, in the steam-engine the heat can only be converted
into mechanical work when it passes from a warmer body (steam) into a
cooler (water); the process cannot be reversed. In the world at large,
however, quite other conditions obtain--conditions which permit the
reconversion of latent heat into mechanical work. For instance, in the
collision of two heavenly bodies, which rush towards each other at
inconceivable speed, enormous quantities of heat are liberated, while
the pulverized masses are hurled and scattered about space. The eternal
drama begins afresh--the rotating mass, the condensation of its parts,
the formation of new meteorites, their combination into larger bodies,
and so on.


The history of the earth, of which we are now going to make a brief
survey, is only a minute section of the history of the cosmos. Like
the latter, it has been the object of philosophic speculation and
mythological fantasy for many thousand years. Its true scientific
study, however, is much younger; it belongs, for the most part, to
the nineteenth century. The fact that the earth is a planet revolving
round the sun was determined by the system of Copernicus (1543);
Galilei, Kepler, and other great astronomers, mathematically determined
its distance from the sun, the laws of its motion, and so forth.
Kant and Laplace indicated, in their cosmogony, the way in which the
earth had been developed from the parent sun. But the later history
of the earth, the formation of its crust, the origin of its seas and
continents, its mountains and deserts, was rarely made the subject
of serious scientific research in the eighteenth century, and in the
first two decades of the nineteenth. As a rule, men were satisfied with
unreliable conjectures or with the traditional story of creation; once
more the Mosaic legend barred the way to an independent investigation.

In 1822 an important work appeared, which followed the same method
in the scientific investigation of the history of the earth that
had already proved the most fertile--the _ontological_ method, or
the principle of "actualism." It consists in a careful study and
manipulation of _actual_ phenomena with a view to the elucidation of
the analogous historical processes of the past. The Society of Science
at Göttingen had offered a prize in 1818 for "the most searching and
comprehensive inquiry into the changes in the earth's crust which are
historically demonstrable, and the application which may be made of a
knowledge of them in the investigation of the terrestrial revolutions
which lie beyond the range of history." This prize was obtained by Karl
Hoff, of Gotha, for his distinguished work, _History of the Natural
Changes in the Crust of the Earth in the Light of Tradition_ (1822-34).
Sir Charles Lyell then applied this _ontological_ or _actualistic_
method with great success to the whole province of geology; his
_Principles of Geology_ (1830) laid the firm foundation on which
the fabric of the history of the earth was so happily erected. The
important geogenetic research of Alexander Humboldt, Leopold Buch,
Gustav Bischof, Edward Süss, and other geologists, were wholly based
on the empirical foundation and the speculative principles of Karl
Hoff and Charles Lyell. They cleared the way for purely rational
science in the field of geology; they removed the obstacles that had
been put in the path by mythological fancy and religious tradition,
especially by the Bible and its legends. I have already discussed the
merits of Lyell, and his relations with his friend Charles Darwin,
in the sixteenth and seventeenth chapters of my _Natural History of
Creation_, and must refer the reader to the standard works on geology
for a further acquaintance with the history of the earth and the great
progress which dynamical and historical geology have made during the

The first division of the history of the earth must be a separation
of inorganic and organic geogeny; the latter begins with the first
appearance of living things on our planet. The earlier section, the
inorganic history of the earth, ran much the same course as that of the
other planets of our system. They were all cast off as rings of nebula
at the equator of the rotating solar mass, and gradually condensed
into independent bodies. After cooling down a little, the glowing ball
of the earth was formed out of the gaseous mass, and eventually, as
the heat continued to radiate out into space, there was formed at its
surface the thin solid crust on which we live. When the temperature at
the surface had gone down to a certain point, the water descended upon
it from the environing clouds of steam, and thus the first condition
was secured for the rise of organic life. Many million years--certainly
more than a hundred--have passed since this important process of
the formation of water took place, introducing the third section of
cosmogony, which we call _biogeny_.


The third phase of the evolution of the world opens with the advent of
organisms on our planet, and continues uninterrupted from that point
until the present day. The great problems which this most interesting
part of the earth's history suggests to us were still thought insoluble
at the beginning of the nineteenth century, or, at least, so difficult
that their solution seemed to be extremely remote. Now, at the close of
the century, we can affirm with legitimate pride that they have been
substantially solved by modern biology and its theory of transformism;
indeed, many of the phenomena of the organic world are now interpreted
on physical principles as completely as the familiar physical phenomena
of inorganic nature. The merit of making the first important step
in this difficult path and of pointing out the way to the monistic
solution of all the problems of biology must be accorded to the great
French scientist, Jean Lamarck; it was in 1809, the year of the
birth of Charles Darwin, that he published his famous _Philosophie
Zoologique_. In this original work not only is a splendid effort made
to interpret all the phenomena of organic life from a monistic and
physical point of view, but the path is opened which alone leads to
the solution of the greatest enigma of this branch of science--the
problem of the natural origin of organic species. Lamarck, who had an
equally extensive empirical acquaintance with zoology and botany, drew
the first sketch of the theory of descent; he showed that all the
countless members of the plant and animal kingdoms have arisen by slow
transformation from simple, common ancestral types, and that it is the
gradual modification of forms by _adaptation_, in reciprocal action
with _heredity_, which has brought about this secular metamorphosis.

I have fully appreciated the merit of Lamarck in the fifth chapter, and
of Darwin in the sixth and seventh chapters, of the _Natural History
of Creation_. Darwin, fifty years afterwards, not only gave a solid
foundation to all the essential parts of the theory of descent, but he
filled up the _lacunae_ of Lamarck's work by his theory of selection.
Darwin reaped abundantly the success that Lamarck had never seen,
with all his merit. His epoch-making work on _The Origin of Species
by Natural Selection_ has transformed modern biology from its very
foundations, in the course of the last forty years, and has raised it
to a stage of development that yields to no other science in existence.
Darwin is _the Copernicus of the organic world_, as I said in 1868, and
E. du Bois-Reymond repeated fifteen years afterwards.[27]


The fourth and last phase of the world's history must be for us men
that latest period of time which has witnessed the development of our
own race. Lamarck (1809) had already recognized that this evolution is
only rationally conceivable as the outcome of a natural process, by
"descent from the apes," our next of kin among the mammals. Huxley then
proved, in his famous essay on _The Place of Man in Nature_, that this
momentous thesis is an inevitable consequence of the theory of descent,
and is thoroughly established by the facts of anatomy, embryology, and
palæontology. He considered this "question of all questions" to be
substantially answered. Darwin followed with a brilliant discussion
of the question under many aspects in his _Descent of Man_ (1871).
I had myself devoted a special chapter to this important problem of
the science of evolution in my _General Morphology_ (1866). In 1874 I
published my _Anthropogeny_, which contains the first attempt to trace
the descent of man through the entire chain of his ancestry right up to
the earliest archigonous monera; the attempt was based equally on the
three great "documents" of evolutionary science--anatomy, embryology,
and palæontology. The progress we have made in anthropogenetic research
during the last few years is described in the paper which I read on
"Our Present Knowledge of the Origin of Man" at the International
Congress of Zoologists at Cambridge in 1898.[28]



    The Monism of the Cosmos--Essential Unity of Organic
    and Inorganic Nature--Carbon-Theory--The Hypothesis of
    Abiogenesis--Mechanical and Purposive Causes--Mechanicism and
    Teleology in Kant's Works--Design in the Organic and Inorganic
    Worlds--Vitalism--Neovitalism--Dysteleology (the Moral of the
    Rudimentary Organs)--Absence of Design in, and Imperfection of,
    Nature--Telic Action in Organized Bodies--Its Absence in Ontogeny
    and Phylogeny--The Platonist "Ideas"--No Moral Order Discoverable
    in the History of the Organic World, of the Vertebrates, or of the
    Human Race--Prevision--Design and Chance

One of the first things to be proved by the law of substance is the
basic fact that any natural force can be directly or indirectly
converted into any other. Mechanical and chemical energy, sound and
heat, light and electricity, are mutually convertible; they seem to be
but different modes of one and the same fundamental force or _energy_.
Thence follows the important thesis of the unity of all natural
forces, or, as it may also be expressed, the "monism of energy."
This fundamental principle is now generally recognized in the entire
province of physics and chemistry, as far as it applies to inorganic

It seems to be otherwise with the organic world and its wealth of
color and form. It is, of course, obvious that a great part of the
phenomena of life may be immediately traced to mechanical and chemical
energy, and to the effects of electricity and light. For other vital
processes, however, especially for psychic activity and consciousness,
such an interpretation is vigorously contested. Yet the modern science
of evolution has achieved the task of constructing a bridge between
these two apparently irreconcilable provinces. We are now certain that
all the phenomena of organic life are subject to the universal law of
substance no less than the phenomena of the inorganic universe.

The unity of nature which necessarily follows, and the demolition of
the earlier dualism, are certainly among the most valuable results of
modern evolution. Thirty-three years ago I made an exhaustive effort
to establish this "monism of the cosmos" and the essential unity of
organic and inorganic nature by a thorough, critical demonstration,
and a comparison of the accordance of these two great divisions of
nature with regard to matter, form, and force.[29] A short epitome of
the result is given in the fifteenth chapter of my _Natural History
of Creation_. The views I put forward are accepted by the majority
of modern scientists, but an attempt has been made in many quarters
lately to dispute them and to maintain the old antithesis of the two
divisions of nature. The ablest of these is to be found in the recent
_Welt als That_ of the botanist Reinke. It defends _pure cosmological_
dualism with admirable lucidity and consistency, and only goes to prove
how utterly untenable the teleological system is that is connected
therewith. According to the author, physical and chemical forces alone
are at work in the entire field of inorganic nature, while in the
organic world we find "intelligent forces," regulative or dominant
forces. The law of substance is supposed to apply to the one, but not
to the other. On the whole, it is a question of the old antithesis of
a mechanical and a teleological system. But before we go more fully
into it, let us glance briefly at two other theories, which seem to
me to be of great importance in the decision of that controversy--the
carbon-theory and the theory of spontaneous generation.

Physiological chemistry has, after countless analyses, established the
following five facts during the last forty years:

I. No other elements are found in organic bodies than those of the
inorganic world.

II. The combinations of elements which are peculiar to organisms,
and which are responsible for their vital phenomena, are compound
protoplasmic substances, of the group of albuminates.

III. Organic life itself is a chemico-physical process, based on the
metabolism (or interchange of material) of these albuminates.

IV. The only element which is capable of building up these compound
albuminates, in combination with other elements (oxygen, hydrogen,
nitrogen, and sulphur), is carbon.

V. These protoplasmic compounds of carbon are distinguished from
most other chemical combinations by their very intricate molecular
structure, their instability, and their jelly-like consistency.

On the basis of these five fundamental facts the following
"carbon-theory" was erected thirty-three years ago: "The peculiar
chemico-physical properties of carbon--especially the fluidity and
the facility of decomposition of the most elaborate albuminoid
compounds of carbon--are the sole and the mechanical causes of
the specific phenomena of movement, which distinguish organic from
inorganic substances, and which are called life, in the usual sense
of the word" (see _The Natural History of Creation_). Although this
"carbon-theory" is warmly disputed in some quarters, no better monistic
theory has yet appeared to replace it. We have now a much better and
more thorough knowledge of the physiological relations of cell-life,
and of the chemistry and physics of the living protoplasm, than we had
thirty-three years ago, and so it is possible to make a more confident
and effective defence of the carbon-theory.

The old idea of spontaneous generation is now taken in many different
senses. It is owing to this indistinctness of the idea, and its
application to so many different hypotheses, that the problem is one
of the most contentious and confused of the science of the day. I
restrict the idea of spontaneous generation--also called abiogenesis
or archigony--to the first development of living protoplasm out of
inorganic carbonates, and distinguish two phases in this "beginning
of biogenesis": (1) _autogony_, or the rise of the simplest
protoplasmic substances in a formative fluid, and (2) _plasmogony_,
the differentiation of individual primitive organisms out of these
protoplasmic compounds, in the form of _monera_. I have treated this
important, though difficult, problem so exhaustively in the fifteenth
chapter of my _Natural History of Creation_ that I may content myself
here with referring to it. There is also a very searching and severely
scientific inquiry into it in my _General Morphology_ (1866). Naegeli
has also treated the hypothesis in quite the same sense in his
mechanico-physiological theory of descent (1884), and has represented
it to be an indispensable thesis in any natural theory of evolution.
I entirely agree with his assertion that "to reject abiogenesis is to
admit a miracle."

The hypothesis of spontaneous generation and the allied carbon-theory
are of great importance in deciding the long-standing conflict between
the _teleological_ (dualistic) and the _mechanical_ (monistic)
interpretation of phenomena. Since Darwin gave us the key to the
monistic explanation of organization in his theory of selection forty
years ago, it has become possible for us to trace the splendid variety
of orderly tendencies of the organic world to mechanical, natural
causes, just as we could formerly in the inorganic world alone. Hence
the supernatural and telic forces, to which the scientist had had
recourse, have been rendered superfluous. Modern metaphysics, however,
continues to regard the latter as indispensable and the former as

No philosopher has done more than Immanuel Kant in defining the
profound distinction between efficient and final causes, with relation
to the interpretation of the whole cosmos. In his well-known earlier
work on _The General Natural History and Theory of the Heavens_ he
made a bold attempt "to treat the constitution and the mechanical
origin of the entire fabric of the universe according to Newtonian
laws." This "cosmological nebular theory" was based entirely on the
mechanical phenomena of gravitation. It was expanded and mathematically
established later on by Laplace. When the famous French astronomer
was asked by Napoleon I. where God, the creator and sustainer of all
things, came in in his system, he clearly and honestly replied: "Sire,
I have managed without that hypothesis." That indicated the atheistic
character which this mechanical cosmogony shares with all the other
inorganic sciences. This is the more noteworthy because the theory of
Kant and Laplace is now almost universally accepted; every attempt to
supersede it has failed. When atheism is denounced as a grave reproach,
as it so often is, it is well to remember that the reproach extends to
the whole of modern science, in so far as it gives a purely mechanical
interpretation of the inorganic world.

Mechanicism (in the Kantian sense) alone can give us a true explanation
of natural phenomena, for it traces them to their real efficient
causes, to blind and unconscious agencies, which are determined in
their action only by the material constitution of the bodies we are
investigating. Kant himself emphatically affirms that "there can be
no science without this mechanicism of nature," and that the capacity
of human reason to give a mechanical interpretation of phenomena is
unlimited. But when he came subsequently to give an elucidation of
the complex phenomena of organic nature in his _critique_ of the
teleological system, he declared that these mechanical causes were
inadequate; that in this we must call _final causes_ to our assistance.
It is true, he said, that even here we must recognize the theoretical
faculty of the mind to give a mechanical interpretation, but its actual
competence to do so is restricted. He grants it this capacity to some
extent; but for the majority of the vital processes (and especially for
man's psychic activity) he thinks we are bound to postulate _final_
causes. The remarkable §79 of the _critique_ of judgment bears the
characteristic heading: "On the Necessity for the Subordination of
the Mechanical Principle to the Teleological in the Explanation of a
Thing as a Natural End." It seemed to Kant so impossible to explain
the orderly processes in the living organism without postulating
supernatural final causes (that is, a purposive creative force) that
he said: "It is quite certain that we cannot even satisfactorily
understand, much less elucidate, the nature of an organism and its
internal faculty on purely mechanical natural principles; it is so
certain, indeed, that we may confidently say, 'It is absurd for a man
to conceive the idea even that some day a Newton will arise who can
explain the origin of a single blade of grass by natural laws which are
uncontrolled by design'--such a hope is entirely forbidden us." Seventy
years afterwards this impossible "Newton of the organic world" appeared
in the person of Charles Darwin, and achieved the great task that Kant
had deemed impracticable.

Since Newton (1682) formulated the law of gravitation, and Kant (1755)
established "the constitution and mechanical origin of the entire
fabric of the world on Newtonian laws," and Laplace (1796) provided
a mathematical foundation for this law of cosmic mechanicism, the
whole of the inorganic sciences have become purely _mechanical_, and
at the same time purely _atheistic_. Astronomy, cosmogony, geology,
meteorology, and inorganic physics and chemistry are now absolutely
ruled by mechanical laws on a mathematical foundation. The idea of
"design" has wholly disappeared from this vast province of science.
At the close of the nineteenth century, now that this monistic view
has fought its way to general recognition, no scientist ever asks
seriously of the "purpose" of any single phenomenon in the whole of
this great field. Is any astronomer likely to inquire seriously to-day
into the purpose of planetary motion, or a mineralogist to seek design
in the structure of a crystal? Does the physicist investigate the
purpose of electric force, or the chemist that of atomic weight? We
may confidently answer in the negative--certainly not, in the sense
that God, or a purposive natural force, had at some time created these
fundamental laws of the mechanism of the universe with a definite
design, and causes them to work daily in accordance with his rational
will. The anthropomorphic notion of a deliberate architect and ruler of
the world has gone forever from this field; the "eternal, iron laws of
nature" have taken his place.

But the idea of design has a very great significance and application
in the _organic_ world. We do undeniably perceive a purpose in the
structure and in the life of an organism. The plant and the animal
seem to be controlled by a definite design in the combination of their
several parts, just as clearly as we see in the machines which man
invents and constructs; as long as life continues the functions of the
several organs are directed to definite ends, just as is the operation
of the various parts of a machine. Hence it was quite natural that the
older naïve study of nature, in explaining the origin and activity
of the living being, should postulate a creator who had "arranged
all things with wisdom and understanding," and had constructed each
plant and animal according to the special purpose of its life. The
conception of this "almighty creator of heaven and earth" was usually
quite anthropomorphic; he created "everything after its kind." As long
as the creator seemed to man to be of human shape, to think with his
brain, see with his eyes, and fashion with his hands, it was possible
to form a definite picture of this "divine engineer" and his artistic
work in the great workshop of creation. This was not so easy when
the idea of God became refined, and man saw in his "invisible God" a
creator without organs--a gaseous being. Still more unintelligible
did these anthropomorphic ideas become when physiology substituted
for the conscious, divine architect an unconscious, creative "vital
force"--a mysterious, purposive, natural force, which differed from the
familiar forces of physics and chemistry, and only took these in part,
during life, into its service. This vitalism prevailed until about the
middle of the nineteenth century. Johannes Müller, the great Berlin
physiologist, was the first to menace it with a destructive dose of
facts. It is true that the distinguished biologist had himself (like
all others in the first half of the century) been educated in a belief
in this vital force, and deemed it indispensable for an elucidation of
the ultimate sources of life; nevertheless, in his classical and still
unrivalled _Manual of Physiology_ (1833) he gave a demonstrative proof
that there is really nothing to be said for this vital force. Müller
himself, in a long series of remarkable observations and experiments,
showed that most of the vital processes in the human organism (and in
the other animals) take place according to physical and chemical laws,
and that many of them are capable of mathematical determination. That
was no less true of the animal functions of the muscles and nerves,
and of both the higher and the lower sense-organs, than of the vegetal
functions of digestion, assimilation, and circulation. Only two
branches of the life of the organism, mental action and reproduction,
retained any element of mystery, and seemed inexplicable without
assuming a vital force. But immediately after Müller's death such
important discoveries and advances were made in these two branches
that the uneasy "phantom of vital force" was driven from its last
refuge. By a very remarkable coincidence Johannes Müller died in the
year 1858, which saw the publication of Darwin's first communication
concerning his famous theory. The theory of selection solved the great
problem that had mastered Müller--the question of the origin of orderly
arrangements from purely mechanical causes.

Darwin, as we have often said, had a twofold immortal merit in the
field of philosophy--firstly, the reform of Lamarck's theory of
descent, and its establishment on the mass of facts accumulated in the
course of the half-century; secondly, the conception of the theory
of selection, which first revealed to us the true causes of the
gradual formation of species. Darwin was the first to point out that
the "struggle for life" is the unconscious regulator which controls
the reciprocal action of heredity and adaptation in the gradual
transformation of species; it is the great "selective divinity" which,
by a purely "natural choice," without preconceived design, creates
new forms, just as selective man creates new types by an "artificial
choice" with a definite design. That gave us the solution of the great
philosophic problem: "How can purposive contrivances be produced by
purely mechanical processes without design?" Kant held the problem to
be insoluble, although Empedocles had pointed out the direction of the
solution two thousand years before. His principle of "teleological
mechanism" has become more and more accepted of late years, and
has furnished a mechanical explanation even of the finest and most
recondite processes of organic life by "the functional self-production
of the purposive structure." Thus have we got rid of the transcendental
"design" of the ideological philosophy of the schools, which was the
greatest obstacle to the growth of a rational and monistic conception
of nature.

Very recently, however, this ancient phantom of a mystic vital force,
which seemed to be effectually banished, has put in a fresh appearance;
a number of distinguished biologists have attempted to reintroduce it
under another name. The clearest presentation of it is to be found in
the _Welt als That_, of the Kiel botanist, J. Reinke. He takes upon
himself the defence of the notion of miracle, of theism, of the Mosaic
story of creation, and of the constancy of species; he calls "vital
forces," in opposition to physical forces, the directive or dominant
forces. Other neovitalists prefer, in the good old anthropomorphic
style, a "supreme" engineer, who has endowed organic substance with a
purposive structure, directed to the realization of a definite plan.
These curious teleological hypotheses, and the objections to Darwinism
which generally accompany them, do not call for serious scientific
refutation to-day.

Thirty-three years ago I gave the title of "dysteleology" to the
science of those extremely interesting and significant biological
facts, which, in the most striking fashion, give a direct contradiction
to the teleological idea "of the purposive arrangement of the living
organism."[30] This "science of rudimentary, abortive, arrested,
distorted, atrophied, and cataplastic individuals" is based on an
immense quantity of remarkable phenomena, which were long familiar to
zoologists and botanists, but were not properly interpreted, and their
great philosophic significance appreciated, until Darwin.

All the higher animals and plants, or, in general, all organisms which
are not entirely simple in structure, but are made up of a number of
organs in orderly co-operation, are found, on close examination, to
possess a number of useless or inoperative members, sometimes, indeed,
hurtful and dangerous. In the flowers of most plants we find, besides
the actual sex-leaves that effect reproduction, a number of other
leaf-organs which have no use or meaning (arrested or "miscarried"
pistils, fruit, corona, and calix-leaves, etc.). In the two large and
variegated classes of flying animals, birds and insects, there are,
besides the forms which make constant use of their wings, a number of
species which have undeveloped wings and cannot fly. In nearly every
class of the higher animals which have eyes there are certain types
that live in the dark; they have eyes, as a rule, but undeveloped and
useless for vision. In our own human organism we have similar useless
rudimentary structures in the muscles of the ear, in the eye-lid, in
the nipple and milk-gland of the male, and in other parts of the body;
indeed, the vermiform appendix of our cæcum is not only useless, but
extremely dangerous, and inflammation of it is responsible for a number
of deaths every year.

Neither the old mystic vitalism nor the new, equally irrational,
neovitalism can give any explanation of these and many other
purposeless contrivances in the structure of the plant and the animal;
but they are very simple in the light of the theory of descent. It
shows that these rudimentary organs are atrophied, owing to disuse.
Just as our muscles, nerves, and organs of sense are strengthened by
exercise and frequent use, so, on the other hand, they are liable to
degenerate more or less by disuse or suspended exercise. But, although
the development of the organs is promoted by exercise and adaptation,
they by no means disappear without leaving a trace after neglect; the
force of heredity retains them for many generations, and only permits
their gradual disappearance after the lapse of a considerable time.
The blind "struggle for existence between the organs" determines their
historical disappearance, just as it effected their first origin and
development. There is no internal "purpose" whatever in the drama.

The life of the animal and the plant bears the same universal character
of incompleteness as the life of man. This is directly attributable
to the circumstance that nature--organic as well as inorganic--is
in a perennial state of evolution, change, and transformation. This
evolution seems on the whole--at least as far as we can survey the
development of organic life on our planet--to be a progressive
improvement, an historical advance from the simple to the complex,
the lower to the higher, the imperfect to the perfect. I have proved
in my _General Morphology_ that this historical progress--or gradual
perfecting (_teleosis_)--is the inevitable result of selection, and not
the outcome of a preconceived design. That is clear from the fact that
no organism is perfect; even if it does perfectly adapt itself to its
environment at a given moment, this condition would not last very long;
the conditions of existence of the environment are themselves subject
to perpetual change and they thus necessitate a continuous adaptation
on the part of the organism.

Under the title of _Design in the Living Organism_, the famous
embryologist, Karl Ernst Baer, published a work in 1876 which, together
with the article on Darwinism which accompanied it, proved very
acceptable to our opponents, and is still much quoted in opposition
to evolution. It was a revival of the old teleological system under
a new name, and we must devote a line of criticism to it. We must
premise that, though Baer was a scientist of the highest order, his
original monistic views were gradually marred by a tinge of mysticism
with the advance of age, and he eventually became a thorough dualist.
In his profound work on "the evolution of animals" (1828), which he
himself entitled _Observation and Experiment_, these two methods of
investigation are equally applied. By careful observation of the
various phenomena of the development of the animal ovum Baer succeeded
in giving the first consistent presentation of the remarkable changes
which take place in the growth of the vertebrate from a simple
egg-cell. At the same time he endeavored, by far-seeing comparison
and keen reflection, to learn the causes of the transformation, and
to reduce them to general constructive laws. He expressed the general
result of his research in the following thesis: "The evolution of
the individual is the story of the growth of individuality in every
respect." He meant that "the one great thought that controls all the
different aspects of animal evolution is the same that gathered the
scattered fragments of space into spheres and linked them into solar
systems. This thought is no other than life itself, and the words and
syllables in which it finds utterance are the varied forms of living

Baer, however, did not attain to a deeper knowledge of this great
genetic truth and a clearer insight into the real efficient causes of
organic evolution, because his attention was exclusively given to
one half of evolutionary science, the science of the evolution of the
individual, embryology, or, in a wider sense, _ontogeny_. The other
half, the science of the evolution of species, _phylogeny_, was not yet
in existence, although Lamarck had already pointed out the way to it in
1809. When it was established by Darwin in 1859, the aged Baer was no
longer in a position to appreciate it; the fruitless struggle which he
led against the theory of selection clearly proved that he understood
neither its real meaning nor its philosophic importance. Teleological
and, subsequently, theological speculations had incapacitated the
ageing scientist from appreciating this greatest reform of biology. The
teleological observations which he published against it in his _Species
and Studies_ in his eighty-fourth year are mere repetitions of errors
which the teleology of the dualists has opposed to the mechanical or
monistic system for more than two thousand years. The "telic idea"
which, according to Baer, controls the entire evolution of the animal
from the ovum, is only another expression for the eternal "idea" of
Plato and the _entelecheia_ of his pupil Aristotle.

Our modern biogeny gives a purely physiological explanation of the
facts of embryology, in assigning the functions of heredity and
adaptation as their causes. The great biogenetic law, which Baer
failed to appreciate, reveals the intimate causal connection between
the _ontogenesis_ of the individual and the _phylogenesis_ of its
ancestors; the former seems to be a recapitulation of the latter.
Nowhere, however, in the evolution of animals and plants do we find any
trace of design, but merely the inevitable outcome of the struggle for
existence, the blind controller, instead of the provident God, that
effects the changes of organic forms by a mutual action of the laws of
heredity and adaptation. And there is no more trace of "design" in the
embryology of the individual plant, animal, or man. This _ontogeny_
is but a brief epitome of _phylogeny_, an abbreviated and condensed
recapitulation of it, determined by the physiological laws of heredity.

Baer ended the preface to his classical _Evolution of Animals_ (1828)
with these words: "The palm will be awarded to the fortunate scientist
who succeeds in reducing the constructive forces of the animal body
to the general forces or life-processes of the entire world. The tree
has not yet been planted which is to make his cradle." The great
embryologist erred once more. That very year, 1828, witnessed the
arrival of Charles Darwin at Cambridge University (for the purpose of
studying theology!)--the "fortunate scientist" who richly earned the
palm thirty years afterwards by his theory of selection.

In the philosophy of history--that is, in the general reflections which
historians make on the destinies of nations and the complicated course
of political evolution--there still prevails the notion of a "moral
order of the universe." Historians seek in the vivid drama of history
a leading design, an ideal purpose, which has ordained one or other
race or state to a special triumph, and to dominion over the others.
This teleological view of history has recently become more strongly
contrasted with our monistic view in proportion as monism has proved
to be the only possible interpretation of inorganic nature. Throughout
the whole of astronomy, geology, physics, and chemistry there is no
question to-day of a "moral order," or a personal God, whose "hand hath
disposed all things in wisdom and understanding." And the same must
be said of the entire field of biology, the whole constitution and
history of organic nature, if we set aside the question of man for the
moment. Darwin has not only proved by his theory of selection that the
orderly processes in the life and structure of animals and plants have
arisen by mechanical laws without any preconceived design, but he has
shown us in the "struggle for life" the powerful natural force which
has exerted supreme control over the entire course of organic evolution
for millions of years. It may be said that the struggle for life is the
"survival of the fittest" or the "victory of the best"; that is only
correct when we regard the strongest as the best (in a moral sense).
Moreover, the whole history of the organic world goes to prove that,
besides the predominant advance towards perfection, there are at all
times cases of retrogression to lower stages. Even Baer's notion of
"design" has no moral feature whatever.

Do we find a different state of things in the history of peoples, which
man, in his anthropocentric presumption, loves to call "the history of
the world"? Do we find in every phase of it a lofty moral principle or
a wise ruler, guiding the destinies of nations? There can be but one
answer in the present advanced stage of natural and human history: No.
The fate of those branches of the human family, those nations and races
which have struggled for existence and progress for thousands of years,
is determined by the same "eternal laws of iron" as the history of the
whole organic world which has peopled the earth for millions of years.

Geologists distinguish three great epochs in the organic history of
the earth, as far as we can read it in the monuments of the science of
fossils--the primary, secondary, and tertiary epochs. According to a
recent calculation, the first occupied at least thirty-four million,
the second eleven million, and the third three million years. The
history of the family of vertebrates, from which our own race has
sprung, unfolds clearly before our eyes during this long period. Three
different stages in the evolution of the vertebrate correspond to the
three epochs; the _fishes_ characterized the primary (palæozoic) age,
the _reptiles_ the secondary (mesozoic), and the _mammals_ the tertiary
(cænozoic). Of the three groups the fishes rank lowest in organization,
the reptiles come next, and the mammals take the highest place. We
find, on nearer examination of the history of the three classes, that
their various orders and families also advanced progressively during
the three epochs towards a higher stage of perfection. May we consider
this progressive development as the outcome of a conscious design or
a moral order of the universe? Certainly not. The theory of selection
teaches us that this organic progress, like the earlier organic
differentiation, is an inevitable consequence of the struggle for
existence. Thousands of beautiful and remarkable species of animals and
plants have perished during those forty-eight million years, to give
place to stronger competitors, and the victors in this struggle for
life were not always the noblest or most perfect forms in a moral sense.

It has been just the same with the history of humanity. The splendid
civilization of classical antiquity perished because Christianity,
with its faith in a loving God and its hope of a better life beyond
the grave, gave a fresh, strong impetus to the soaring human mind. The
Papal Church quickly degenerated into a pitiful caricature of real
Christianity, and ruthlessly scattered the treasures of knowledge
which the Hellenic philosophy had gathered; it gained the dominion
of the world through the ignorance of the credulous masses. In time
the Reformation broke the chains of this mental slavery, and assisted
reason to secure its right once more. But in the new, as in the
older, period the great struggle for existence went on in its eternal
fluctuation, with no trace of a moral order.

And it is just as impossible for the impartial and critical observer
to detect a "wise providence" in the fate of individual human beings
as a moral order in the history of peoples. Both are determined with
iron necessity by a mechanical causality which connects every single
phenomenon with one or more antecedent causes. Even the ancient Greeks
recognized _ananke_, the blind _heimarmene_, the fate "that rules
gods and men," as the supreme principle of the universe. Christianity
replaced it by a conscious Providence, which is not blind, but sees,
and which governs the world in patriarchal fashion. The anthropomorphic
character of this notion, generally closely connected with belief in
a personal God, is quite obvious. Belief in a "loving Father," who
unceasingly guides the destinies of one billion five hundred million
men on our planet, and is attentive at all times to their millions of
contradictory prayers and pious wishes, is absolutely impossible; that
is at once perceived on laying aside the colored spectacles of "faith"
and reflecting rationally on the subject.

As a rule, this belief in Providence and the tutelage of a "loving
Father" is more intense in the modern civilized man--just as in the
uncultured savage--when some good fortune has fallen him: an escape
from peril of life, recovery from a severe illness, the winning of the
first prize in a lottery, the birth of a long-delayed child, and so
forth. When, on the other hand, a misfortune is met with, or an ardent
wish is not fulfilled, "Providence" is forgotten. The wise ruler of the
world slumbered--or refused his blessing.

In the extraordinary development of commerce of the nineteenth century
the number of catastrophes and accidents has necessarily increased
beyond all imagination; of that the journal is a daily witness.
Thousands are killed every year by shipwreck, railway accidents, mine
accidents, etc. Thousands slay each other every year in war, and the
preparation for this wholesale massacre absorbs much the greater part
of the revenue in the highest civilized nations, the chief professors
of "Christian charity." And among these hundreds of thousands of annual
victims of modern civilization strong, industrious, courageous workers
predominate. Yet the talk of a "moral order" goes on.

Since impartial study of the evolution of the world teaches us that
there is no definite aim and no special purpose to be traced in it,
there seems to be no alternative but to leave everything to "blind
chance." This reproach has been made to the transformism of Lamarck and
Darwin, as it had been to the previous systems of Kant and Laplace;
there are a number of dualist philosophers who lay great stress on it.
It is, therefore, worth while to make a brief remark upon it.

One group of philosophers affirms, in accordance with its teleological
conception, that the whole cosmos is an orderly system, in which every
phenomenon has its aim and purpose; there is no such thing as chance.
The other group, holding a mechanical theory, expresses itself thus:
The development of the universe is a monistic mechanical process, in
which we discover no aim or purpose whatever; what we call design in
the organic world is a special result of biological agencies; neither
in the evolution of the heavenly bodies nor in that of the crust of
our earth do we find any trace of a controlling purpose--all is the
result of chance. Each party is right--according to its definition of
chance. The general law of causality, taken in conjunction with the law
of substance, teaches us that every phenomenon has a mechanical cause;
in this sense there is no such thing as chance. Yet it is not only
lawful, but necessary, to retain the term for the purpose of expressing
the simultaneous occurrence of two phenomena, which are not causally
related to each other, but of which each has its own mechanical cause,
independent of that of the other. Everybody knows that chance, in its
monistic sense, plays an important part in the life of man and in the
universe at large. That, however, does not prevent us from recognizing
in each "chance" event, as we do in the evolution of the entire
cosmos, the universal sovereignty of nature's supreme law, _the law of



    The Idea of God in General--Antithesis of God and the World; the
    Supernatural and Nature--Theism and Pantheism--Chief Forms of
    Statistics--Naturalistic Monotheism--Solarism--Anthropistic
    Monotheism--The Three Great Mediterranean
    Religions--Mosaism--Christianity--The Cult of the Madonna and
    the Saints--Papal Polytheism--Islam--Mixotheism--Nature of
    Theism--An Extra-mundane and Anthropomorphic God; a Gaseous
    Vertebrate--Pantheism--Intramundane God (Nature)--The Hylozoism
    of the Ionic Monists (Anaximander)--Conflict of Pantheism and
    Christianity--Spinoza--Modern Monism--Atheism

For thousands of years humanity has placed the last and supreme basis
of all phenomena in an efficient cause, to which it gives the title of
God (_deus_, _theos_). Like all general ideas, this notion of God has
undergone a series of remarkable modifications and transformations in
the course of the evolution of reason. Indeed, it may be said that no
other idea has had so many metamorphoses; for no other belief affects
in so high a degree the chief objects of the mind and of rational
science, as well as the deepest interests of the emotion and poetic
fancy of the believer.

A comparative criticism of the many different forms of the idea of God
would be extremely interesting and instructive; but we have not space
for it in the present work. We must be content with a passing glance
at the most important forms of the belief and their relation to the
modern thought that has been evoked by a sound study of nature. For
further information on this interesting question the reader would do
well to consult the distinguished work of Adalbert Svoboda, _Forms of
Faith_ (1897).

When we pass over the finer shades and the variegated clothing of
the God-idea and confine our attention to its chief element, we can
distribute all the different presentations of it in two groups--the
_theistic_ and _pantheistic_ group. The latter is closely connected
with the monistic, or rational, view of things, and the former is
associated with dualism and mysticism.


In this view God is distinct from, and opposed to, the world as its
creator, sustainer, and ruler. He is always conceived in a more or
less human form, as an organism which thinks and acts like a man--only
on a much higher scale. This anthropomorphic God, polyphyletically
evolved by the different races, assumes an infinity of shapes in their
imagination, from fetichism to the refined monotheistic religions
of the present day. The chief forms of theism are polytheism,
triplotheism, amphitheism, and monotheism.

The polytheist peoples the world with a variety of gods and goddesses,
which enter into its machinery more or less independently. _Fetichism_
sees such subordinate deities in the lifeless body of nature, in rocks,
in water, in the air, in human productions of every kind (pictures,
statues, etc.). _Demonism_ sees gods in living organisms of every
species--trees, animals, and men. This kind of polytheism is found in
innumerable forms even in the lowest tribes. It reaches the highest
stage in Hellenic polytheism, in the myths of ancient Greece, which
still furnish the finest images to the modern poet and artist. At a
much lower stage we have Catholic polytheism, in which innumerable
"saints" (many of them of very equivocal repute) are venerated as
subordinate divinities, and prayed to to exert their mediation with the
supreme divinity.

The dogma of the "Trinity," which still comprises three of the chief
articles of faith in the creed of Christian peoples, culminates in the
notion that the one God of Christianity is really made up of _three_
different persons: (1) God the Father, the omnipotent creator of heaven
and earth (this untenable myth was refuted long ago by scientific
cosmogony, astronomy, and geology); (2) Jesus Christ; and (3) the Holy
Ghost, a mystical being, over whose incomprehensible relation to the
Father and the Son millions of Christian theologians have racked their
brains in vain for the last nineteen hundred years. The Gospels, which
are the only clear sources of this _triplotheism_, are very obscure as
to the relation of these three persons to each other, and do not give a
satisfactory answer to the question of their unity. On the other hand,
it must be carefully noted what confusion this obscure and mystic dogma
of the Trinity must necessarily cause in the minds of our children even
in the earlier years of instruction. One morning they learn (in their
religious instruction) that three times one are one, and the very next
hour they are told in their arithmetic class that three times one are
three. I remember well the reflection that this confusion led me to in
my early school-days.

For the rest, the "Trinity" is not an original element in Christianity;
like most of the other Christian dogmas, it has been borrowed from
earlier religions. Out of the sun-worship of the Chaldean magi was
evolved the Trinity of Ilu, the mysterious source of the world; its
three manifestations were Anu, primeval chaos; Bel, the architect of
the world; and Aa, the heavenly light, the all-enlightening wisdom.
In the Brahmanic religion the Trimurti is also conceived as a "divine
unity" made up of three persons--Brahma (the creator), Vishnu (the
sustainer), and Shiva (the destroyer). It would seem that in this
and other ideas of a Trinity the "sacred number, three," as such--as
a "symbolical number"--has counted for something. The three first
Christian virtues--Faith, Hope, and Charity--form a similar _triad_.

According to the _amphitheists_, the world is ruled by two different
gods, a good and an evil principle, God and the Devil. They are engaged
in a perpetual struggle, like rival emperors, or pope and anti-pope.
The condition of the world is the result of this conflict. The
loving God, or good principle, is the source of all that is good and
beautiful, of joy and of peace. The world would be perfect if His work
were not continually thwarted by the evil principle, the Devil; this
being is the cause of all that is bad and hateful, of contradiction and
of pain.

Amphitheism is undoubtedly the most rational of all forms of belief in
God, and the one which is least incompatible with a scientific view
of the world. Hence we find it elaborated in many ancient peoples
thousands of years before Christ. In ancient India Vishnu, the
preserver, struggles with Shiva, the destroyer. In ancient Egypt the
good Osiris is opposed by the wicked Typhon. The early Hebrews had a
similar dualism of Aschera (or Keturah), the fertile mother-earth,
and Elion (Moloch or Sethos), the stern heavenly father. In the Zend
religion of the ancient Persians, founded by Zoroaster two thousand
years before Christ, there is a perpetual struggle between Ormuzd, the
good god of light, and Ahriman, the wicked god of darkness.

In Christian mythology the Devil is scarcely less conspicuous as the
adversary of the good deity, the tempter and seducer, the prince of
hell, and lord of darkness. A personal devil was still an important
element in the belief of most Christians at the beginning of the
nineteenth century. Towards the middle of the century he was gradually
eliminated by being progressively explained away, or he was restricted
to the subordinate _rôle_ he plays as Mephistopheles in Goethe's great
drama. To-day the majority of educated people look upon "belief in a
personal devil" as a mediæval superstition, while "belief in God" (that
is, the personal, good, and loving God) is retained as an indispensable
element of religion. Yet the one belief is just as much (or as little)
justified as the other. In any case, the much-lamented "imperfection of
our earthly life," the "struggle for existence," and all that pertains
to it, are explained much more simply and naturally by this struggle of
a good and an evil god than by any other form of theism.

The dogma of the unity of God may in some respects be regarded as the
simplest and most natural type of theism; it is popularly supposed to
be the most widely accepted element of religion, and to predominate
in the ecclesiastical systems of civilized countries. In reality,
that is not the case, because this alleged "monotheism" usually turns
out on closer inquiry to be one of the other forms of theism we have
examined, a number of subordinate deities being generally introduced
besides the supreme one. Most of the religions which took a purely
monotheistic stand-point have become more or less polytheistic in the
course of time. Modern statistics assure us that of the one billion
five hundred million men who people the earth the great majority
are monotheists; of these, _nominally_, about six hundred millions
are Brahma-Buddhists, five hundred millions are called Christians,
two hundred millions are heathens (of various types), one hundred
and eighty millions are Mohammedans, ten millions are Jews, and ten
millions have no religion at all. However, the vast majority of
these nominal monotheists have very confused ideas about the deity,
or believe in a number of gods and goddesses besides the chief
god--angels, devils, etc.

The different forms which monotheism has assumed in the course of its
polyphyletic development may be distributed in two groups--those of
_naturalistic_ and _anthropistic_ monotheism. Naturalistic monotheism
finds the embodiment of the deity in some lofty and dominating natural
phenomenon. The sun, the deity of light and warmth, on whose influence
all organic life insensibly and directly depends, was taken to be
such a phenomenon many thousand years ago. Sun-worship (solarism,
or heliotheism) seems to the modern scientist to be the best of all
forms of theism, and the one which may be most easily reconciled
with modern monism. For modern astrophysics and geogeny have taught
us that the earth is a fragment detached from the sun, and that it
will eventually return to the bosom of its parent. Modern physiology
teaches us that the first source of organic life on the earth is the
formation of protoplasm, and that this synthesis of simple inorganic
substances, water, carbonic acid, and ammonia, only takes place under
the influence of sunlight. On the primary evolution of the plasmodomous
plants followed, secondarily, that of the plasmophagous animals, which
directly or indirectly depend on them for nourishment; and the origin
of the human race itself is only a later stage in the development of
the animal kingdom. Indeed, the whole of our bodily and mental life
depends, in the last resort, like all other organic life, on the
light and heat rays of the sun. Hence in the light of pure reason,
sun-worship, as a form of naturalistic monotheism, seems to have a much
better foundation than the anthropistic worship of Christians and of
other monotheists who conceive their god in human form. As a matter of
fact, the sun-worshippers attained, thousands of years ago, a higher
intellectual and moral standard than most of the other theists. When
I was in Bombay, in 1881, I watched with the greatest sympathy the
elevating rites of the pious Parsees, who, standing on the sea-shore,
or kneeling on their prayer-rugs, offered their devotion to the sun at
its rise and setting.[31]

Moon-worship (lunarism and selenotheism) is of much less importance
than sun-worship. There are a few uncivilized races that have adored
the moon as their only deity, but it has generally been associated with
a worship of the stars and the sun.

The humanization of God, or the idea that the "Supreme Being" feels,
thinks, and acts like man (though in a higher degree), has played a
most important part, as _anthropomorphic monotheism_, in the history
of civilization. The most prominent in this respect are the three
great religions of the Mediterranean peoples--the old Mosaic religion,
the intermediate Christian religion, and the younger Mohammedanism.
These three great Mediterranean religions, all three arising on the
east coast of the most interesting of all seas, and originating in an
imaginative enthusiast of the Semitic race, are intimately connected,
not only by this external circumstance of an analogous origin, but by
many common features of their internal contents. Just as Christianity
borrowed a good deal of its mythology directly from ancient Judaism, so
Islam has inherited much from both its predecessors. All the three were
originally monotheistic; all three were subsequently overlaid with a
great variety of polytheistic features, in proportion as they extended,
first along the coast of the Mediterranean with its heterogeneous
population, and eventually into every part of the world.

The Hebrew monotheism, as it was founded by Moses (about 1600 B.C.), is
usually regarded as the ancient faith which has been of the greatest
importance in the ethical and religious development of humanity.
This high historical appreciation is certainly valid in the sense
that the two other world-conquering Mediterranean religions issued
from it; Christ was just as truly a pupil of Moses as Mohammed was
afterwards of Christ. So also the New Testament, which has become the
foundation of the belief of the highest civilized nations in the short
space of nineteen hundred years, rests on the venerable basis of the
Old Testament. The Bible, which the two compose, has had a greater
influence and a wider circulation than any other book in the world.
Even to-day the Bible--in spite of its curious mingling of the best and
the worst elements--is in a certain sense the "book of books." Yet when
we make an impartial and unprejudiced study of this notable historical
source, we find it very different in several important respects from
the popular impression. Here again modern criticism and history have
come to certain conclusions which destroy the prevalent tradition in
its very foundations.

The monotheism which Moses endeavored to establish in the worship
of Jehovah, and which the prophets--the philosophers of the Hebrew
race--afterwards developed with great success, had at first to sustain
a long and severe struggle with the dominant polytheism which was
in possession. Jehovah, or Yahveh, was originally derived from the
heaven-god, which, under the title of Moloch or Baal, was one of
the most popular of the Oriental deities (the Sethos or Typhon of
the Egyptians, and the Saturn or Cronos of the Greeks). There were,
however, other gods in great favor with the Jewish people, and so the
struggle with "idolatry" continued. Still, Jehovah was, in principle,
the only God, explicitly claiming, in the first precept of the
decalogue: "I am the Lord thy God; thou shalt have no other gods beside

Christian monotheism shared the fate of its mother, Mosaism; it was
generally only monotheistic in theory, while it degenerated practically
into every kind of polytheism. In point of fact, monotheism was
logically abandoned in the very dogma of the Trinity, which was adopted
as an indispensable foundation of the Christian religion. The three
persons, which are distinguished as Father, Son, and Holy Ghost, are
three distinct individuals (and, indeed, anthropomorphic persons), just
as truly as the three Indian deities of the Trimurti (Brahma, Vishnu,
and Shiva) or the Trinity of the ancient Hebrews (Anu, Bel, and Aa).
Moreover, in the most widely distributed form of Christianity the
"virgin" mother of Christ plays an important part as a fourth deity;
in many Catholic countries she is practically taken to be much more
powerful and influential than the three male persons of the celestial
administration. The cult of the madonna has been developed to such an
extent in these countries that we may oppose it to the usual masculine
form of monotheism as one of a feminine type. The "Queen of Heaven"
becomes so prominent, as is seen in so many pictures and legends of the
madonna, that the three male persons practically disappear.

In addition, the imagination of the pious Christian soon came to
increase this celestial administration by a numerous company of
"saints" of all kinds, and bands of musical angels, who should see
that "eternal life" should not prove too dull. The popes--the greatest
charlatans that any religion ever produced--have constantly studied to
increase this band of celestial satellites by repeated canonizations.
This curious company received its most interesting acquisition in 1870,
when the Vatican Council pronounced the popes, as the vicars of Christ,
to be infallible, and thus raised them to a divine dignity. When we add
the "personal Devil" that they acknowledge, and the "bad angels" who
form his court, we have in modern Catholicism, still the most extensive
branch of Christianity, a rich and variegated polytheism that dwarfs
the Olympic family of the Greeks.

Islam, or the Mohammedan monotheism, is the youngest and purest form of
monotheism. When the young Mohammed (born 570) learned to despise the
polytheistic idolatry of his Arabian compatriots, and became acquainted
with Nestorian Christianity, he adopted its chief doctrines in a
general way; but he could not bring himself to see anything more than
a prophet in Christ, like Moses. He found in the dogma of the Trinity
what every emancipated thinker finds on impartial reflection--an
absurd legend which is neither reconcilable with the first principles
of reason nor of any value whatever for our religious advancement. He
justly regarded the worship of the immaculate mother of God as a piece
of pure idolatry, like the veneration of pictures and images. The
longer he reflected on it, and the more he strove after a purified idea
of deity, the clearer did the certitude of his great maxim appear: "God
is the only God"--there are no other gods beside him.

Yet Mohammed could not free himself from the anthropomorphism of the
God-idea. His one only God was an idealized, almighty man, like the
stern, vindictive God of Moses, and the gentle, loving God of Christ.
Still, we must admit that the Mohammedan religion has preserved the
character of pure monotheism throughout the course of its historical
development and its inevitable division much more faithfully than the
Mosaic and Christian religions. We see that to-day, even externally,
in its forms of prayer and preaching, and in the architecture and
adornment of its mosques. When I visited the East for the first time,
in 1873, and admired the noble mosques of Cairo, Smyrna, Brussa, and
Constantinople, I was inspired with a feeling of real devotion by the
simple and tasteful decoration of the interior, and the lofty and
beautiful architectural work of the exterior. How noble and inspiring
do these mosques appear in comparison with the majority of Catholic
churches, which are covered internally with gaudy pictures and gilt,
and are outwardly disfigured by an immoderate crowd of human and
animal figures! Not less elevated are the silent prayers and the
simple devotional acts of the Koran when compared with the loud,
unintelligible verbosity of the Catholic Mass and the blatant music of
their theatrical processions.

Under the title of _mixotheism_ we may embrace all the forms of
theistic belief which contain mixtures of religious notions of
different, sometimes contradictory, kinds. In theory this most widely
diffused type of religion is not recognized at all; in the concrete
it is the most important and most notable of all. The vast majority
of men who have religious opinions have always been, and still are,
_mixotheists_; their idea of God is picturesquely compounded from the
impressions received in childhood from their own sect, and a number
of other impressions which are received later on, from contact with
members of other religions, and which modify the earlier notions. In
educated people there is also sometimes the modifying influence of
philosophic studies in maturer years, and especially the unprejudiced
study of natural phenomena, which reveals the futility of the theistic
idea. The conflict of these contradictory impressions, which is
very painful to a sensitive soul, and which often remains undecided
throughout life, clearly shows the immense power of the _heredity_ of
ancient myths on the one hand and the early _adaptation_ to erroneous
dogmas on the other. The particular faith in which the child has been
brought up generally remains in power, unless a "conversion" takes
place subsequently, owing to the stronger influence of some other
religion. But even in this supersession of one faith by another the new
name, like the old one, proves to be merely an outward label covering
a mixture of the most diverse opinions and errors. The greater part
of those who call themselves Christians are not monotheists (as they
think), but amphitheists, triplotheists, or polytheists. And the same
must be said of Islam and Mosaism, and other monotheistic religions.
Everywhere we find associated with the original idea of a "sole and
triune God" later beliefs in a number of subordinate deities--angels,
devils, saints, etc.--a picturesque assortment of the most diverse
theistic forms.

All the above forms of theism, in the proper sense of the word--whether
the belief assumes a naturalistic or an anthropistic form--represent
God to be an extramundane or a supernatural being. He is always opposed
to the world, or nature, as an independent being; generally as its
creator, sustainer, and ruler. In most religions he has the additional
character of personality, or, to put it more definitely still, God as
a person is likened to man. "In his gods man paints himself." This
anthropomorphic conception of God as one who thinks, feels, and acts
like man prevails with the great majority of theists, sometimes in a
cruder and more naïve form, sometimes in a more refined and abstract
degree. In any case the form of theosophy we have described is sure
to affirm that God, the supreme being, is infinite in perfection, and
therefore far removed from the imperfection of humanity. Yet, when we
examine closely, we always find the same psychic or mental activity in
the two. God feels, thinks, and acts as man does, although it be in an
infinitely more perfect form.

The _personal anthropism_ of God has become so natural to the majority
of believers that they experience no shock when they find God
personified in human form in pictures and statues, and in the varied
images of the poet, in which God takes human form--that is, is changed
into a vertebrate. In some myths, even, God takes the form of other
mammals (an ape, lion, bull, etc.), and more rarely of a bird (eagle,
dove, or stork), or of some lower vertebrate (serpent, crocodile,
dragon, etc.).

In the higher and more abstract forms of religion this idea of bodily
appearance is entirely abandoned, and God is adored as a "pure spirit"
without a body. "God is a spirit, and they who worship him must worship
him in spirit and in truth." Nevertheless, the psychic activity of this
"pure spirit" remains just the same as that of the anthropomorphic
God. In reality, even this immaterial spirit is not conceived to be
incorporeal, but merely invisible, gaseous. We thus arrive at the
paradoxical conception of God as a _gaseous vertebrate_.


Pantheism teaches that God and the world are one. The idea of God is
identical with that of nature or substance. This pantheistic view is
sharply opposed in principle to all the systems we have described, and
to all possible forms of theism although there have been many attempts
made from both sides to bridge over the deep chasm that separates the
two. There is always this fundamental contradiction between them, that
in theism God is opposed to nature as an _extramundane_ being, as
creating and sustaining the world, and acting upon it from without,
while in pantheism God, as an _intramundane_ being, is everywhere
identical with nature itself, and is operative _within_ the world
as "force" or "energy." The latter view alone is compatible with
our supreme law--the law of substance. It follows necessarily that
pantheism is _the world-system of the modern scientist_. There are,
it is true, still a few men of science who contest this, and think it
possible to reconcile the old theistic theory of human nature with the
pantheistic truth of the law of substance. All these efforts rest on
confusion or sophistry--when they are honest.

As pantheism is a result of an advanced conception of nature in the
civilized mind, it is naturally much younger than theism, the crudest
forms of which are found in great variety in the uncivilized races of
ten thousand years ago. We do, indeed, find the germs of pantheism in
different religions at the very dawn of philosophy in the earliest
civilized peoples (in India, Egypt, China, and Japan), several thousand
years before the time of Christ; still, we do not meet a definite
philosophical expression of it until the hylozoism of the Ionic
philosophers, in the first half of the sixth century before Christ.
All the great thinkers of this flourishing period of Hellenic thought
are surpassed by the famous Anaximander, of Miletus, who conceived the
essential unity of the infinite universe (_apeiron_) more profoundly
and more clearly than his master, Thales, or his pupil, Anaximenes.
Not only the great thought of the original unity of the cosmos and the
development of all phenomena out of the all-pervading primitive matter
found expression in Anaximander, but he even enunciated the bold idea
of countless worlds in a periodic alternation of birth and death.

Many other great philosophers of classical antiquity, especially
Democritus, Heraclitus, and Empedocles, had, in the same or an
analogous sense, a profound conception of this unity of nature and
God, of body and spirit, which has obtained its highest expression
in the law of substance of our modern monism. The famous Roman poet
and philosopher, Lucretius Carus, has presented it in a highly poetic
form in his poem "De Rerum Natura." However, this true pantheistic
monism was soon entirely displaced by the mystic dualism of Plato, and
especially by the powerful influence which the idealistic philosophy
obtained by its blending with Christian dogmas. When the papacy
attained to its spiritual despotism over the world, pantheism was
hopelessly crushed; Giordano Bruno, its most gifted defender, was
burned alive by the "Vicar of Christ" in the Campo dei Fiori at Rome on
February 17, 1600.

It was not until the middle of the seventeenth century that pantheism
was exhibited in its purest form by the great Baruch Spinoza; he gave
for the totality of things a definition of substance in which God
and the world are inseparably united. The clearness, confidence, and
consistency of Spinoza's monistic system are the more remarkable when
we remember that this gifted thinker of two hundred and fifty years
ago was without the support of all those sound empirical bases which
have been obtained in the second half of the nineteenth century. We
have already spoken, in the first chapter, of Spinoza's relation to the
materialism of the eighteenth and the monism of the nineteenth century.
The propagation of his views, especially in Germany, is due, above
all, to the immortal works of our greatest poet and thinker, Wolfgang
Goethe. His splendid _God and the World_, _Prometheus_, _Faust_, etc.,
embody the great thoughts of pantheism in the most perfect poetic

Atheism affirms that there are no gods or goddesses, assuming that
god means a personal, extramundane entity. This "godless world-system"
substantially agrees with the monism or pantheism of the modern
scientist; it is only another expression for it, emphasizing its
negative aspect, the non-existence of any supernatural deity. In this
sense Schopenhauer justly remarks: "Pantheism is only a polite form
of atheism. The truth of pantheism lies in its destruction of the
dualist antithesis of God and the world, in its recognition that the
world exists in virtue of its own inherent forces. The maxim of the
pantheist, 'God and the world are one,' is merely a polite way of
giving the Lord God his _congé_."

During the whole of the Middle Ages, under the bloody despotism of the
popes, atheism was persecuted with fire and sword as a most pernicious
system. As the "godless" man is plainly identified with the "wicked"
in the Gospel, and is threatened--simply on account of his "want of
faith"--with the eternal fires of hell, it was very natural that every
good Christian should be anxious to avoid the suspicion of atheism.
Unfortunately, the idea still prevails very widely. The atheistic
scientist who devotes his strength and his life to the search for
the truth, is freely credited with all that is evil; the theistic
church-goer, who thoughtlessly follows the empty ceremonies of Catholic
worship, is at once assumed to be a good citizen, even if there be no
meaning whatever in his faith and his morality be deplorable. This
error will only be destroyed when, in the twentieth century, the
prevalent superstition gives place to rational knowledge and to a
monistic conception of the unity of God and the world.



    The Knowledge of the Truth and Its Sources: the Activity of the
    Senses and the Association of Presentations--Organs of Sense and
    Organs of Thought--Sense-Organs and their Specific Energy--Their
    Evolution--The Philosophy of Sensibility--Inestimable Value of the
    Senses--Limits of Sensitive Knowledge--Hypothesis and Faith--Theory
    and Faith--Essential Difference of Scientific (Natural) and
    Religious (Supernatural) Faith--Superstition of Savage and of
    Civilized Races--Confessions of Faith--Unsectarian Schools--The
    Faith of Our Fathers--Spiritism--Revelation

Every effort of genuine science makes for a knowledge of the truth. Our
only real and valuable knowledge is a knowledge of nature itself, and
consists of presentations which correspond to external things. We are
incompetent, it is true, to penetrate into the innermost nature of this
real world--the "thing in itself"--but impartial critical observation
and comparison inform us that, in the normal action of the brain and
the organs of sense, the impressions received by them from the outer
world are the same in all rational men, and that in the normal function
of the organs of thought certain presentations are formed which are
everywhere the same. These presentations we call _true_, and we are
convinced that their content corresponds to the knowable aspect of
things. We _know_ that these facts are not imaginary, but real.

All knowledge of the truth depends on two different, but intimately
connected, groups of human physiological functions: firstly, on the
_sense-impressions_ of the object by means of sense-action, and,
secondly, on the combination of these impressions by an association
into _presentations_ in the subject. The instruments of sensation are
the sense-organs (_sensilla_ or _aestheta_); the instruments which
form and link together the presentations are the organs of thought
(_phroneta_). The latter are part of the central, and the former part
of the peripheral, nervous system--that important and elaborate system
of organs in the higher animals which alone effects their entire
psychic activity.

Man's sense-activity, which is the starting-point of all knowledge,
has been slowly and gradually developed from that of his nearest
mammal relatives, the primates. The sense-organs are of substantially
the same construction throughout this highest animal group, and their
function takes place always according to the same physical and chemical
laws. They have had the same historical development in all cases. In
the mammals, as in the case of all other animals, the _sensilla_ were
originally parts of the skin; the sensitive cells of the epidermis are
the sources of all the different sense-organs, which have acquired
their specific energy by adaptation to different stimuli (light, heat,
sound, chemical action, etc.). The rod-cells in the retina of the eye,
the auditory cells in the cochlea of the ear, the olfactory cells in
the nose, and the taste-cells on the tongue, are all originally derived
from the simple, indifferent cells of the epidermis, which cover the
entire surface of the body. This significant fact can be directly
proved by observation of the embryonic development of man or any of the
higher animals. And from this ontogenetic fact we confidently infer,
in virtue of the great biogenetic law, the important phylogenetic
proposition, that in the long historical evolution of our ancestors,
likewise, the higher sense-organs with their specific energies were
originally derived from the epidermis of lower animals, from a simple
layer of cells which had no trace of such differentiated sensilla.

A particular importance attaches to the circumstance that different
nerves are qualified to perceive different properties of the
environment, and these only. The optic nerve accomplishes only the
perception of light, the auditory nerve the perception of sound, the
olfactory nerve the perception of smell, and so on. No matter what
stimuli impinge on and irritate a given sense-organ, its reaction
is always of the same character. From this specific energy of the
sense-nerves, which was first fully appreciated by Johannes Müller,
very erroneous inferences have been drawn, especially in favor of a
dualistic and _à priori_ theory of knowledge. It has been affirmed
that the brain, or the soul, only perceives a certain condition of the
stimulated nerve, and that, consequently, no conclusion can be drawn
from the process as to the existence and nature of the stimulating
environment. Sceptical philosophy concluded that the very existence of
an outer world is doubtful, and extreme idealism went on positively to
deny it, contending that things only exist in our impressions of them.

In opposition to these erroneous views, we must recall the fact that
the "specific energy" was not originally an innate, special quality of
the various nerves, but it has arisen by adaptation to the particular
activity of the epidermic cells in which they terminate. In harmony
with the great law of "division of labor" the originally indifferent
"sense-cells of the skin" undertook different tasks, one group of them
taking over the stimulus of the light rays, another the impress of the
sound waves, a third the chemical impulse of odorous substances, and so
on. In the course of a very long period these external stimuli effected
a gradual change in the physiological, and later in the morphological,
properties of these parts of the epidermis, and there was a correlative
modification of the sensitive nerves which conduct the impressions they
receive to the brain. Selection improved, step by step, such particular
modifications as proved to be useful, and thus eventually, in the
course of many million years, created those wonderful instruments,
the eye and the ear, which we prize so highly; their structure is
so remarkably purposive that they might well lead to the erroneous
assumption of a "creation on a preconceived design." The peculiar
character of each sense-organ and its specific nerve has thus been
gradually evolved by use and exercise--that is, by _adaptation_--and
has then been transmitted by _heredity_ from generation to generation.
Albrecht Rau has thoroughly established this view in his excellent
work on _Sensation and Thought_, a physiological inquiry into the
nature of the human understanding (1896). It points out the correct
significance of Müller's law of specific sense-energies, adding
searching investigations into their relation to the brain, and in the
last chapter there is an able "philosophy of sensitivity" based on the
ideas of Ludwig Feuerbach. I thoroughly agree with his convincing work.

Critical comparison of sense-action in man and the other vertebrates
has brought to light a number of extremely important facts, the
knowledge of which we owe to the penetrating research of the
nineteenth century, especially of the second half of the century. This
is particularly true of the two most elaborate "æsthetic" organs,
the eye and the ear. They present a different and more complicated
structure in the vertebrates than in the other animals, and have also
a characteristic development in the embryo. This typical ontogenesis
and structure of the sensilla of all the vertebrates is only explained
by _heredity_ from a common ancestor. Within the vertebrate group,
however, we find a great variety of structure in points of detail, and
this is due to _adaptation_ to their manner of life on the part of the
various species, to the increasing or diminishing use of various parts.

In respect of the structure of his sense-organs man is by no means
the most perfect and most highly-developed vertebrate. The eye of the
eagle is much keener, and can distinguish small objects at a distance
much more clearly than the human eye. The hearing of many mammals,
especially of the carnivora, ungulata, and rodentia of the desert, is
much more sensitive than that of man, and perceives slight noises at a
much greater distance; that may be seen at a glance by their large and
very sensitive cochlea. Singing birds have attained a higher grade of
development, even in respect of musical endowment, than the majority of
men. The sense of smell is much more developed in most of the mammals,
especially in the carnivora and the ungulata, than in man; if the dog
could compare his own fine scent with that of man, he would look down
on us with compassion. Even with regard to the lower senses--taste,
sex-sense, touch, and temperature--man has by no means reached the
highest stage in every respect.

We can naturally only pass judgment on the sensations which we
ourselves experience. However, anatomy informs us of the presence in
the bodies of many animals of other senses than those we are familiar
with. Thus fishes and other lower aquatic vertebrates have peculiar
sensilla in the skin which are in connection with special sense-nerves.
On the right and left sides of the fish's body there is a long canal,
branching into a number of smaller canals at the head. In this "mucous
canal" there are nerves with numerous branches, the terminations of
which are connected with peculiar nerve-aggregates. This extensive
epidermic sense-organ probably serves for the perception of changes in
the pressure, or in other properties, of the water. Some groups are
distinguished by the possession of other peculiar sensilla, the meaning
of which is still unknown to us.

But it is already clear from the above facts that our human
sense-activity is limited, not only in quantity, but in quality also.
We can thus only perceive with our senses, especially with the eye
and the sense of touch, a part of the qualities of the objects in our
environment. And even this partial perception is incomplete, in the
sense that our organs are imperfect, and our sensory nerves, acting
as interpreters, communicate to the brain only a translation of the
impressions received.

However, this acknowledged imperfection of our senses should not
prevent us from recognizing their instruments, and especially the eye,
to be organs of the highest type; together with the thought-organs in
the brain, they are nature's most valuable gift to man. Very truly does
Albrecht Rau say: "All science is sensitive knowledge in the ultimate
analysis; it does not deny, but interpret, the data of the senses.
The senses are our first and best friends. Long before the mind is
developed the senses tell man what he must do and avoid. He who makes
a general disavowal of the senses in order to meet their dangers acts
as thoughtlessly and as foolishly as the man who plucks out his eyes
because they once fell on shameful things, or the man who cuts off
his hand lest at any time it should reach out to the goods of his
neighbor." Hence Feuerbach is quite right in calling all philosophies,
religions, and systems which oppose the principle of sense-action not
only erroneous, but really pernicious. Without the senses there is
no knowledge--"_Nihil est in intellectu, quod non fuerit in sensu_,"
as Locke said. Twenty years ago I pointed out, in my chapter "On the
Origin and Development of the Sense-Organs,"[32] the great service of
Darwinism in giving us a profounder knowledge and a juster appreciation
of the senses.

The thirst for knowledge of the educated mind is not contented with
the defective acquaintance with the outer world which is obtained
through our imperfect sense-organs. He endeavors to build up the
sense-impressions which they have brought him into valuable knowledge.
He transforms them into specific sense-perceptions in the sense-centres
of the cortex of the brain, and combines them into presentations,
by association, in the thought-centres. Finally, by a further
concatenation of the groups of presentations he attains to connected
knowledge. But this knowledge remains defective and unsatisfactory
until the imagination supplements the inadequate power of combination
of the intelligence, and, by the association of stored-up images,
unites the isolated elements into a connected whole. Thus are produced
new general presentative images, and these suffice to interpret the
facts perceived and satisfy "reason's feeling of causality."

The presentations which fill up the gaps in our knowledge, or take its
place, may be called, in a broad sense, "faith." That is what happens
continually in daily life. When we are not sure about a thing we say, I
believe it. In this sense we are compelled to make use of faith even in
science itself; we conjecture or assume that a certain relation exists
between two phenomena, though we do not know it for certain. If it is
a question of a _cause_, we form a _hypothesis_; though in science
only such hypotheses are admitted as lie within the sphere of human
cognizance, and do not contradict known facts. Such hypotheses are, for
instance--in physics the theory of the vibratory movement of ether, in
chemistry the hypothesis of atoms and their affinity, in biology the
theory of the molecular structure of living protoplasm, and so forth.

The explanation of a great number of connected phenomena by the
assumption of a common cause is called a _theory_. Both in theory and
hypothesis "faith" (in the scientific sense) is indispensable; for
here again it is the imagination that fills up the gaps left by the
intelligence in our knowledge of the connection of things. A theory,
therefore, must always be regarded only as an approximation to the
truth; it must be understood that it may be replaced in time by another
and better-grounded theory. But, in spite of this admitted uncertainty,
theory is indispensable for all true science; it elucidates facts by
postulating a cause for them. The man who renounces theory altogether,
and seeks to construct a pure science with certain facts alone
(as often happens with wrong-headed representatives of our "exact
sciences"), must give up the hope of any knowledge of causes, and,
consequently, of the satisfaction of reason's demand for causality.

The theory of gravitation in astronomy (Newton), the nebular theory
in cosmogony (Kant and Laplace), the principle of energy in physics
(Meyer and Helmholtz), the atomic theory in chemistry (Dalton), the
vibratory theory in optics (Huyghens), the cellular theory in histology
(Schleiden and Schwann), and the theory of descent in biology (Lamarck
and Darwin), are all important theories of the first rank; they explain
a whole world of natural phenomena by the assumption of a common cause
for all the several facts of their respective provinces, and by showing
that all the phenomena thereof are inter-connected and controlled by
laws which issue from this common cause. Yet the cause itself may
remain obscure in character, or be merely a "provisional hypothesis."
The "force of gravity" in the theory of gravitation and in cosmogony,
"energy" itself in its relation to matter, the "ether" of optics
and electricity, the "atom" of the chemist, the living "protoplasm"
of histology, the "heredity" of the evolutionist--these and similar
conceptions of other great theories may be regarded by a sceptical
philosophy as "mere hypotheses" and the outcome of scientific "faith,"
yet they are indispensable for us, until they are replaced by better

The dogmas which are used for the explanation of phenomena in the
various religions, and which go by the name of "faith" (in the narrower
sense), are of a very different character from the forms of scientific
faith we have enumerated. The two types, however--the "natural"
faith of science and the "supernatural" faith of religion--are not
infrequently confounded, so that we must point out their fundamental
difference. Religious faith means always belief in a miracle, and as
such is in hopeless contradiction with the natural faith of reason.
In opposition to reason it postulates supernatural agencies, and,
therefore, may be justly called superstition. The essential difference
of this superstition from rational faith lies in the fact that it
assumes supernatural forces and phenomena, which are unknown and
inadmissible to science, and which are the outcome of illusion and
fancy; moreover, superstition contradicts the well-known laws of
nature, and is therefore _irrational_.

Owing to the great progress of ethnology during the century, we
have learned a vast quantity of different kinds and practices of
superstition, as they still survive in uncivilized races. When they are
compared with each other and with the mythological notion of earlier
ages, a manifold analogy is discovered, frequently a common origin, and
eventually one simple source for them all. This is found in the "demand
of causality in reason," in the search for an explanation of obscure
phenomena by the discovery of a cause. That applies particularly to
such phenomena as threaten us with danger and excite fear, like thunder
and lightning, earthquakes, eclipses, etc. The demand for a causal
explanation of such phenomena is found in uncivilized races of the
lowest grade, transmitted from their primate ancestors by heredity. It
is even found in many other vertebrates. When a dog barks at the full
moon, or at a ringing bell, of which it sees the hammer moving, or at a
flag that flutters in the breeze, it expresses not only fear, but also
the mysterious impulse to learn the cause of the obscure phenomenon.
The crude beginnings of religion among primitive races spring partly
from this hereditary superstition of their primate ancestors, and
partly from the worship of ancestors, from various emotional impulses,
and from habits which have become traditional.

The religious notions of modern civilized peoples, which they esteem
so highly, profess to be on a much higher level than the "crude
superstition" of the savage; we are told of the great advance which
civilization has made in sweeping it aside. That is a great mistake.
Impartial comparison and analysis show that they only differ in
their special "form of faith" and the outer shell of their creed.
In the clear light of reason the refined faith of the most liberal
ecclesiastical religion--inasmuch as it contradicts the known and
inviolable laws of nature--is no less irrational a superstition than
the crude spirit-faith of primitive fetichism on which it looks down
with proud disdain.

And if, from this impartial stand-point, we take a critical glance at
the kinds of faith that prevail to-day in civilized countries, we find
them everywhere saturated with traditional superstition. The Christian
belief in Creation, the Trinity, the Immaculate Conception, the
Redemption, the Resurrection and Ascension of Christ, and so forth, is
just as purely imaginative as the belief in the various dogmas of the
Mohammedan, Mosaic, Buddhistic, and Brahmanic religions, and is just
as incapable of reconciliation with a rational knowledge of nature.
Each of these religions is for the sincere believer an indisputable
truth, and each regards the other as heresy and damnable error. The
more confidently a particular sect considers itself "the only ark
of salvation," and the more ardently this conviction is cherished,
the more zealously does it contend against all other sects and give
rise to the fearful religious wars that form the saddest pages in the
book of history. And all the time the unprejudiced "critique of pure
reason" teaches us that all these different forms of faith are equally
false and irrational, mere creatures of poetic fancy and uncritical
tradition. Rational science must reject them all alike as the outcome
of superstition.

The incalculable injury which irrational superstition has done
to credulous humanity is conspicuously revealed in the ceaseless
conflict of confessions of faith. Of all the wars which nations have
waged against each other with fire and sword the religious wars have
been the bloodiest; of all the forms of discord that have shattered
the happiness of families and of individuals those that arise from
religious differences are still the most painful. Think of the millions
who have lost their lives in Christian persecutions, in the religious
conflicts of Islam and of the Reformation, by the Inquisition, and
under the charge of witchcraft. Or think of the still greater number
of luckless men who, through religious differences, have been plunged
into family troubles, have lost the esteem of their fellow-citizens
and their position in the community, or have even been compelled to
fly from their country. The official confession of faith becomes most
pernicious of all when it is associated with the political aims of
a modern state, and is enforced as "religious instruction" in our
schools. The child's mind is thus early diverted from the pursuit of
the truth and impregnated with superstition. Every friend of humanity
should do all in his power to promote unsectarian schools as one of the
most valuable institutions of the modern state.

The great value which is, none the less, still very widely attached
to sectarian instruction is not only due to the compulsion of a
reactionary state and its dependence on a dominant clericalism, but
also to the weight of old traditions and "emotional cravings" of
various kinds. One of the strongest of these is the devout reverence
which is extended everywhere to sectarian tradition, to the "faith
of our fathers." In thousands of stories and poems fidelity to it
is extolled as a spiritual treasure and a sacred duty. Yet a little
impartial study of the history of faith suffices to show the absurdity
of the notion. The dominant evangelical faith of the second half of
the nineteenth century is essentially different from that of the first
half, and this again from that of the eighteenth century. The faith of
the eighteenth century diverges considerably from the "faith of our
fathers" of the seventeenth, and still more from that of the sixteenth,
century. The Reformation, releasing enslaved reason from the tyranny of
the popes, is naturally regarded by them as darkest heresy; but even
the faith of the papacy itself had been completely transformed in the
course of a century. And how different is the faith of the Christian
from that of his heathen ancestors. Every man with some degree of
independent thought frames a more or less personal religion for
himself, which is always different from that of his fathers; it depends
largely on the general condition of thought in his day. The further we
go back in the history of civilization, the more clearly do we find
this esteemed "faith of our fathers" to be an indefensible superstition
which is undergoing continual transformation.

One of the most remarkable forms of superstition, which still takes a
very active part in modern life, is _spiritism_. It is a surprising
and a lamentable fact that millions of educated people are still
dominated by this dreary superstition; even distinguished scientists
are entangled in it. A number of spiritualist journals spread the
faith far and wide, and our "superior circles" do not scruple to hold
_séances_ in which "spirits" appear, rapping, writing, giving messages
from "the beyond," and so on. It is a frequent boast of spiritists that
even eminent men of science defend their superstition. In Germany, A.
Zöllner and Fechner are quoted as instances; in England, Wallace and
Crookes. The regrettable circumstance that physicists and biologists
of such distinction have been led astray by spiritism is accounted
for, partly by their excess of imagination and defect of critical
faculty, and partly by the powerful influence of dogmas which a
religious education imprinted on the brain in early youth. Moreover,
it was precisely through the famous _séances_ at Leipzig, in which the
physicists, Zöllner, Fechner, and Wilhelm Weber, were imposed on by
the clever American conjuror, Slade, that the fraud of the latter was
afterwards fully exposed; he was discovered to be a common impostor.
In other cases, too, where the alleged marvels of spiritism have been
thoroughly investigated, they have been traced to a more or less clever
deception; the mediums (generally of the weaker sex) have been found to
be either smart swindlers or nervous persons of abnormal irritability.
Their supposed gift of "telepathy" (or "action at a distance of thought
without material medium") has no more existence than the "voices" or
the "groans" of spirits, etc. The vivid pictures which Carl du Prel, of
Munich, and other spiritists give of their phenomena must be regarded
as the outcome of a lively imagination, together with a lack of
critical power and of knowledge of physiology.

The majority of religions have, in spite of their great differences,
one common feature, which is, at the same time, one of their strongest
supports in many quarters. They declare that they can elucidate the
problem of existence, the solution of which is beyond the natural power
of reason, by the supernatural way of revelation; from that they derive
the authority of the dogmas which in the guise of "divine laws" control
morality and the practical conduct of life. "Divine" inspirations of
that kind form the basis of many myths and legends, the human origin of
which is perfectly clear. It is true that the God who reveals himself
does not always appear in human shape, but in thunder and lightning,
storm and earthquake, fiery bush or menacing cloud. But the revelation
which he is supposed to bring to the credulous children of men is
always anthropomorphic; it invariably takes the form of a communication
of ideas or commands which are formulated and expressed precisely as is
done in the normal action of the human brain and larynx. In the Indian
and Egyptian religions, in the mythologies of Greece and Rome, in the
Old and the New Testaments, the gods think, talk, and act just as men
do; the revelations, in which they are supposed to unveil for us the
secrets of existence and the solution of the great world-enigma, are
creations of the human imagination. The "truth" which the credulous
discover in them is a human invention; the "childlike faith" in these
irrational revelations is mere superstition.

The true revelation--that is, the true source of rational knowledge--is
to be sought in nature alone. The rich heritage of truth which forms
the most valuable part of human culture is derived exclusively from
the experiences acquired in a searching study of nature, and from the
rational conclusions which it has reached by the just association of
these empirical presentations. Every intelligent man with normal brain
and senses finds this true revelation in nature on impartial study, and
thus frees himself from the superstition with which the "revelations"
of religion had burdened him.



    Increasing Opposition between Modern Science and Christian
    Theology--The Old and the New Faith--Defence of Rational Science
    against the Attacks of Christian Superstition, especially against
    Catholicism--Four Periods in the Evolution of Christianity:
    I. Primitive Christianity (the First Three Centuries)--The
    Four Canonical Gospels--The Epistles of Paul--II. The Papacy
    (Ultramontane Christianity)--Retrogression of Civilization in the
    Middle Ages--Ultramontane Falsification of History--The Papacy and
    Science--The Papacy and Christianity--III. The Reformation--Luther
    and Calvin--The Year of Emancipation--IV. The Pseudo-Christianity
    of the Nineteenth Century--The Papal Declaration of War against
    Reason and Science: (_a_) Infallibility, (_b_) The Encyclica, (_c_)
    The Immaculate Conception

One of the most distinctive features of the expiring century is
the increasing vehemence of the opposition between science and
Christianity. That is both natural and inevitable. In the same
proportion in which the victorious progress of modern science has
surpassed all the scientific achievements of earlier ages has the
untenability been proved of those mystic views which would subdue
reason under the yoke of an alleged revelation; and the Christian
religion belongs to that group. The more solidly modern astronomy,
physics, and chemistry have established the sole dominion of inflexible
natural laws in the universe at large, and modern botany, zoology,
and anthropology have proved the validity of those laws in the entire
kingdom of organic nature, so much the more strenuously has the
Christian religion, in association with dualistic metaphysics, striven
to deny the application of these natural laws in the province of the
so-called "spiritual life"--that is, in one section of the physiology
of the brain.

No one has more clearly, boldly, and unanswerably enunciated this
open and irreconcilable opposition between the modern scientific and
the outworn Christian view than David Friedrich Strauss, the greatest
theologian of the nineteenth century. His last work, _The Old Faith
and the New_, is a magnificent expression of the honest conviction of
all educated people of the present day who understand this unavoidable
conflict between the discredited, dominant doctrines of Christianity
and the illuminating, rational revelation of modern science--all
those who have the courage to defend the right of reason against the
pretensions of superstition, and who are sensible of the philosophic
demand for a unified system of thought. Strauss, as an honorable and
courageous free-thinker, has expounded far better than I could the
principal points of difference between "the old and the new faith."
The absolute irreconcilability of the opponents and the inevitability
of their struggle ("for life or death") have been ably presented on
the philosophic side by E. Hartmann, in his interesting work on _The
Self-Destruction of Christianity_.

When the works of Strauss and Feuerbach and _The History of the
Conflict between Religion and Science_ of J. W. Draper have been read,
it may seem superfluous for us to devote a special chapter to the
subject. Yet we think it useful, and even necessary for our purpose,
to cast a critical glance at the historical course of this great
struggle; especially seeing that the attacks of the "Church militant"
on science in general, and on the theory of evolution in particular,
have become extremely bitter and menacing of late years. Unfortunately,
the mental relaxation which has lately set in, and the rising flood of
reaction in the political, social, and ecclesiastical world, are only
too well calculated to give point to those dangers. If any one doubts
it, he has only to look over the conduct of Christian synods and of the
German Reichstag during the last few years. Quite in harmony are the
recent efforts of many secular governments to get on as good a footing
as possible with the "spiritual regiment," their deadly enemy--that
is, to submit to its yoke. The two forces find a common aim in the
suppression of free thought and free scientific research, for the
purpose of thus more easily securing a complete despotism.

Let us first emphatically protest that it is a question for us of the
necessary defence of science and reason against the vigorous attacks
of the Christian Church and its vast army, not of an unprovoked
attack of science on religion. And, in the first place, our defence
must be prepared against Romanism or Ultramontanism. This "one ark
of salvation," this Catholic Church "destined for all," is not only
much larger and more powerful than the other Christian sects, but it
has the exceptional advantage of a vast, centralized organization
and an unrivalled political ability. Men of science are often heard
to say that the Catholic superstition is no more astute than the
other forms of supernatural faith, and that all these insidious
institutions are equally inimical to reason and science. As a matter
of general theoretical principle the statement may pass, but it is
certainly wrong when we look to its practical side. The deliberate and
indiscriminate attacks of the ultramontane Church on science, supported
by the apathy and ignorance of the masses, are, on account of its
powerful organization, much more severe and dangerous than those of
other religions.

In order to appreciate correctly the extreme importance of Christianity
in regard to the entire history of civilization, and particularly
its fundamental opposition to reason and science, we must briefly
run over the principal stages of its historical evolution. It may be
divided into four periods: (1) primitive Christianity (the first three
centuries), (2) papal Christianity (twelve centuries, from the fourth
to the fifteenth), (3) the Reformation (three centuries, from the
sixteenth to the eighteenth), and (4) modern pseudo-Christianity.


Primitive Christianity embraces the first three centuries. Christ
himself, the noble prophet and enthusiast, so full of the love of
humanity, was far below the level of classical culture; he knew nothing
beyond the Jewish traditions; he has not left a single line of writing.
He had, indeed, no suspicion of the advanced stage to which Greek
philosophy and science had progressed five hundred years before.

All that we know of him and of his original teaching is taken from the
chief documents of the New Testament--the four gospels and the Pauline
epistles. As to the four canonical gospels, we now know that they were
selected from a host of contradictory and forged manuscripts of the
first three centuries by the three hundred and eighteen bishops who
assembled at the Council of Nicæa in 327. The entire list of gospels
numbered forty; the canonical list contains four. As the contending
and mutually abusive bishops could not agree about the choice, they
determined to leave the selection to a miracle. They put all the books
(according to the _Synodicon_ of Pappus) together underneath the
altar, and prayed that the apocryphal books, of human origin, might
remain there, and the genuine, inspired books might be miraculously
placed on the table of the Lord. And that, says tradition, really
occurred! The three synoptic gospels (Matthew, Mark, and Luke--all
written _after_ them, not _by_ them, at the beginning of the second
century) and the very different fourth gospel (ostensibly "after"
John, written about the middle of the second century) leaped on the
table, and were thenceforth recognized as the inspired (with their
thousand mutual contradictions) foundations of Christian doctrine. If
any modern "unbeliever" finds this story of the "leap of the sacred
books" incredible, we must remind him that it is just as credible as
the table-turning and spirit-rapping that are believed to take place
to-day by millions of educated people; and that hundreds of millions of
Christians believe just as implicitly in their personal immortality,
their "resurrection from the dead," and the Trinity of God--dogmas that
contradict pure reason no more and no less than that miraculous bound
of the gospel manuscripts.

The most important sources after the gospels are the fourteen separate
(and generally forged) epistles of Paul. The genuine Pauline epistles
(_three_ in number, according to recent criticism--to the Romans,
Galatians, and Corinthians) were written before the canonical gospels,
and contain less incredible miraculous matter than they. They are
also more concerned than the gospels to adjust themselves with a
rational view of the world. Hence the advanced theology of modern times
constructs its "ideal Christianity" rather on the base of the Pauline
epistles than on the gospels, so that it has been called "Paulinism."

The remarkable personality of Paul, who possessed much more culture
and practical sense than Christ, is extremely interesting, from the
anthropological point of view, from the fact that the racial origin
of the two great religious founders is very much the same. Recent
historical investigation teaches that Paul's father was of Greek
nationality, and his mother of Jewish.[33] The half-breeds of these two
races, which are so very distant in origin (although they are branches
of the same species, the _homo mediterraneus_), are often distinguished
by a happy blending of talents and temperament, as we find in many
recent and actual instances. The plastic Oriental imagination and the
critical Western reason often admirably combine and complete each
other. That is visible in the Pauline teaching, which soon obtained a
greater influence than the earliest Christian notions. Hence it is not
incorrect to consider Paulinism a new phenomenon, of which the father
was the philosophy of the Greeks, and the mother the religion of the
Jews. Neoplatonism is an analogous combination.

As to the real teaching and aims of Christ (and as to many important
aspects of his life) the views of conflicting theologians diverge
more and more, as historical criticism (Strauss, Feuerbach, Baur,
Renan, etc.) puts the accessible facts in their true light, and draws
impartial conclusions from them. Two things, certainly, remain beyond
dispute--the lofty principle of universal charity and the fundamental
maxim of ethics, the "golden rule," that issues therefrom; both,
however, existed in theory and in practice centuries before the time
of Christ (cf. chap. xix.). For the rest, the Christians of the early
centuries were generally pure Communists, sometimes "Social Democrats,"
who, according to the prevailing theory in Germany to-day, ought to
have been exterminated with fire and sword.


Latin Christianity, variously called Papistry, Romanism, Vaticanism,
Ultramontanism, or the Roman Catholic Church, is one of the most
remarkable phenomena in the history of civilized man; in spite of
the storms that have swept over it, it still exerts a most powerful
influence. Of the four hundred and ten million Christians who are
scattered over the earth the majority--that is, two hundred and
twenty-five millions--are Roman Catholics; there are seventy-five
million Greek Catholics and one hundred and ten million Protestants.
During a period of one thousand two hundred years, from the fourth to
the sixteenth century, the papacy has almost absolutely controlled and
tainted the spiritual life of Europe; on the other hand, it has won but
little territory from the ancient religions of Asia and Africa. In Asia
Buddhism still counts five hundred and three million followers, the
Brahmanic religion one hundred and thirty-eight millions, and Islam one
hundred and twenty millions.

It is the despotism of the papacy that lent its darkest character to
the Middle Ages; it meant death to all freedom of mental life, decay
to all science, corruption to all morality. From the noble height to
which the life of the human mind had attained in classical antiquity,
in the centuries before Christ and the first century after Christ,
it soon sank, under the rule of the papacy, to a level which, in
respect of the knowledge of the truth, can only be termed barbarism.
It is often protested that other aspects of mental life--poetry and
architecture, scholastic learning and patristic philosophy--were richly
developed in the Middle Ages. But this activity was in the service of
the Church; it did not tend to the cultivation, but to the suppression,
of free mental research. The exclusive preparing for an unknown
eternity beyond the tomb, the contempt of nature, the withdrawal from
the study of it, which are essential elements of Christianity, were
urged as a sacred duty by the Roman hierarchy. It was not until the
beginning of the sixteenth century that a change for the better came in
with the Reformation.

It is impossible for us here to describe the pitiful retrogression
of culture and morality during the twelve centuries of the spiritual
despotism of Rome. It is very pithily expressed in a saying of the
greatest and the ablest of the Hohenzollerns; Frederick the Great
condensed his judgment in the phrase that the study of history led
one to think that from Constantine to the date of the Reformation the
whole world was insane. L. Büchner has given us an admirable, brief
description of this "period of insanity" in his work on _Religious
and Scientific Systems_. The reader who desires a closer acquaintance
with the subject would do well to consult the historical works of
Ranke, Draper, Kolb, Svoboda, etc. The truthful description of the
awful condition of the Christian Middle Ages, which is given by these
and other unprejudiced historians, is confirmed by all the reliable
sources of investigation, and by the historical monuments which
have come down from the saddest period of human history. Educated
Catholics, who are sincere truth-seekers, cannot be too frequently
recommended to study these historical sources for themselves. This is
the more necessary as ultramontane literature has still a considerable
influence. The old trick of deceiving the faithful by a complete
reversal of facts and an invention of miraculous circumstances is
still worked by it with great success. We will only mention Lourdes
and the "Holy Coat" of Trêves. The ultramontane professor of history
at Frankfurt, Johannes Janssen, affords a striking example of the
length they will go in distorting historical truth; his much-read works
(especially his _History of the German People since the Middle Ages_)
are marred by falsification to an incredible extent. The untruthfulness
of these Jesuitical productions is on a level with the credulity and
the uncritical judgment of the simple German nation that takes them for

One of the most interesting of the historical facts which clearly prove
the evil of the ultramontane despotism is its vigorous and consistent
struggle with science. This was determined on, in principle, from the
very beginning of Christianity, inasmuch as it set faith above reason
and preached the blind subjection of the one to the other; that was
natural, seeing that our whole life on earth was held to be only a
preparation for the legendary life beyond, and thus scientific research
was robbed of any real value. The deliberate and successful attack on
science began in the early part of the fourth century, particularly
after the Council of Nicæa (327), presided over by Constantine--called
the "Great" because he raised Christianity to the position of a state
religion, and founded Constantinople, though a worthless character,
a false-hearted hypocrite, and a murderer. The success of the papacy
in its conflict with independent scientific thought and inquiry is
best seen in the distressing condition of science and its literature
during the Middle Ages. Not only were the rich literary treasures
that classical antiquity had bequeathed to the world destroyed for
the most part, or withdrawn from circulation, but the rack and the
stake insured the silence of every heretic--that is, every independent
thinker. If he did not keep his thoughts to himself, he had to look
forward to being burned alive, as was the fate of the great monistic
philosopher, Giordano Bruno, the reformer, John Huss, and more than a
hundred thousand other "witnesses to the truth." The history of science
in the Middle Ages teaches us on every page that independent thought
and empirical research were completely buried for twelve sad centuries
under the oppression of the omnipotent papacy.

All that we esteem in true Christianity, in the sense of its founder
and of his noblest followers, and that we must endeavor to save from
the inevitable wreck of this great world religion for our new monistic
religion, lies on its ethical and social planes. The principles of
true humanism, the golden rule, the spirit of tolerance, the love
of man, in the best and highest sense of the word--all these true
graces of Christianity were not, indeed, first discovered and given
to the world by that religion, but were successfully developed in the
critical period when classical antiquity was hastening to its doom.
The papacy, however, has attempted to convert all those virtues into
the direct contrary, and still to hang out the sign of the old firm.
Instead of Christian charity, it introduced a fanatical hatred of the
followers of all other religions; with fire and sword it has pursued,
not only the heathen, but every Christian sect that dared resist the
imposition of ultramontane dogma. Tribunals for heretics were erected
all over Europe, yielding unnumbered victims, whose torments seemed
only to fill their persecutors, with all their Christian charity, with
a peculiar satisfaction. The power of Rome was directed mercilessly
for centuries against everything that stood in its way. Under the
notorious Torquemada (1481-98), in Spain alone eight thousand heretics
were burned alive and ninety thousand punished with the confiscation
of their goods and the most grievous ecclesiastical fines; in the
Netherlands, under the rule of Charles V., at least fifty thousand
men fell victims to the clerical bloodthirst. And while the heavens
resounded with the cry of the martyrs, the wealth of half the world was
pouring into Rome, to which the whole of Christianity paid tribute, and
the self-styled representatives of God on earth and their accomplices
(not infrequently Atheists themselves) wallowed in pleasure and vice
of every description. "And all these privileges," said the frivolous,
syphilitic Pope, Leo X., "have been secured to us by the fable of Jesus

Yet, with all the discipline of the Church and the fear of God, the
condition of European society was pitiable. Feudalism, serfdom, the
grace of God, and the favor of the monks ruled the land; the poor
helots were only too glad to be permitted to raise their miserable
huts under the shadow of the castle or the cloister, their secular and
spiritual oppressors and exploiters. Even to-day we suffer from the
aftermath of these awful ages and conditions, in which there was no
question of care for science or higher mental culture save in rare
circumstances and in secret. Ignorance, poverty, and superstition
combined with the immoral operation of the law of celibacy, which
had been introduced in the eleventh century, to consolidate the
ever-growing power of the papacy. It has been calculated that there
were more than ten million victims of fanatical religious hatred during
this "Golden Age" of papal domination; and how many more million human
victims must be put to the account of celibacy, oral confession, and
moral constraint, the most pernicious and accursed institutions of
the papal despotism! Unbelieving philosophers, who have collected
disproofs of the existence of God, have overlooked one of the strongest
arguments in that sense--the fact that the Roman "Vicar of Christ"
could for twelve centuries perpetrate with impunity the most shameful
and horrible deeds "in the name of God."


The history of civilization, which we are so fond of calling "the
history of the world," enters upon its third period with the
Reformation of the Christian Church, just as its second period begins
with the founding of Christianity. With the Reformation begins the
new birth of fettered reason, the reawakening of science, which the
iron hand of the Christian papacy had relentlessly crushed for twelve
hundred years. At the same time the spread of general education had
already commenced, owing to the invention of printing about the
middle of the fifteenth century; and towards its close several great
events occurred, especially the discovery of America in 1492, which
prepared the way for the "renaissance" of science in company with
that of art. Indeed, certain very important advances were made in the
knowledge of nature during the first half of the sixteenth century,
which shook the prevailing system to its very foundations. Such were
the circumnavigation of the globe by Magellan in 1522, which afforded
empirical proof of its rotundity, and the founding of the new system of
the world by Copernicus in 1543.

Yet the 31st of October in the year 1517, the day on which Martin
Luther nailed his ninety-five theses to the wooden door of Wittenburg
Cathedral, must be regarded as the commencement of a new epoch; for
on that day was forced the iron door of the prison in which the Papal
Church had detained fettered reason for twelve hundred years. The
merits of the great reformer have been partly exaggerated, partly
underestimated. It has been justly pointed out that Luther, like all
the other reformers, remained in manifold subjection to the deepest
superstition. Thus he was throughout life a supporter of the rigid
dogma of the verbal inspiration of the Bible; he zealously maintained
the doctrines of the resurrection, original sin, predestination,
justification by faith, etc. He rejected as folly the great discovery
of Copernicus, because in the Bible "Joshua bade the sun, not the
earth, stand still." He utterly failed to appreciate the great
political revolutions of his time, especially the profound and just
agitation of the peasantry. Worse still was the fanatical Calvin, of
Geneva, who had the talented Spanish physician, Serveto, burned alive
in 1553, because he rejected the absurd dogma of the Trinity. The
fanatical "true believers" of the reformed Church followed only too
frequently in the blood-stained footsteps of their papal enemies; as
they do even in our own day. Deeds of unparalleled cruelty followed
in the train of the Reformation--the massacre of St. Bartholomew and
the persecution of the Huguenots in France, bloody heretic-hunts in
Italy, civil war in England, and the Thirty Years War in Germany. Yet,
in spite of those grave blemishes, to the sixteenth and seventeenth
centuries belongs the honor of once more opening a free path to the
thoughtful mind, and delivering reason from the oppressive yoke of the
papacy. Thus only was made possible that great development of different
tendencies in critical philosophy and of new paths in science which
won for the subsequent eighteenth century the honorable title of "the
century of enlightenment."


As the fourth and last stage in the history of Christianity we oppose
our nineteenth century to all its predecessors. It is true that the
enlightenment of preceding centuries had promoted critical thought in
every direction, and the rise of science itself had furnished powerful
empirical weapons; yet it seems to us that our progress along both
lines has been quite phenomenal during the nineteenth century. It
has inaugurated an entirely new period in the history of the human
mind, characterized by the development of the monistic philosophy
of nature. At its very commencement the foundations were laid of a
new anthropology (by the comparative anatomy of Cuvier) and of a new
biology (by the _Philosophie Zoologique_ of Lamarck). The two great
French scientists were quickly succeeded by two contemporary German
scholars--Baer, the founder of the science of evolution, and Johannes
Müller, the founder of comparative morphology and physiology. A
pupil of Müller, Theodor Schwann, created the far-reaching cellular
theory in 1838, in conjunction with M. Schleiden. Lyell had already
traced the evolution of the earth to natural causes, and thus proved
the application to our planet of the mechanical cosmogony which Kant
had sketched with so much insight in 1755. Finally, Robert Mayer and
Helmholtz established the principle of energy in 1842--the second,
complementary half of the great law of substance, the first half of
which (the persistence of matter) had been previously discovered by
Lavoisier. Forty years ago Charles Darwin crowned all these profound
revelations of the intimate nature of the universe by his new theory
of evolution, the greatest natural-philosophical achievement of our

What is the relation of modern Christianity to this vast and
unparalleled progress of science? In the first place, the deep gulf
between its two great branches, conservative Romanism and progressive
Protestantism, has naturally widened. The ultramontane clergy (and
we must associate with them the orthodox "evangelical alliance") had
naturally to offer a strenuous opposition to this rapid advance of
the emancipated mind; they continued unmoved in their rigid literal
belief, demanding the unconditional surrender of reason to dogma.
Liberal Protestantism, on the other hand, took refuge in a kind of
monistic pantheism, and sought a means of reconciling two contradictory
principles. It endeavored to combine the unavoidable recognition of
the established laws of nature, and the philosophic conclusions that
followed from them, with a purified form of religion, in which scarcely
anything remained of the distinctive teaching of faith. There were
many attempts at compromise to be found between the two extremes; but
the conviction rapidly spread that dogmatic Christianity had lost every
foundation, and that only its valuable ethical contents should be saved
for the new monistic religion of the twentieth century. As, however,
the existing external forms of the dominant Christian religion remained
unaltered, and as, in spite of a progressive political development,
they are more intimately than ever connected with the practical needs
of the State, there has arisen that widespread religious profession
in educated spheres which we can only call "pseudo-Christianity"--at
the bottom it is a "religious lie" of the worst character. The great
dangers which attend this conflict between sincere conviction and the
hypocritical profession of modern pseudo-Christians are admirably
described in Max Nordau's interesting work on _The Conventional Lies of

In the midst of this obvious falseness of prevalent pseudo-Christianity
there is one favorable circumstance for the progress of a rational
study of nature: its most powerful and bitterest enemy, the Roman
Church, threw off its mask of ostensible concern for higher mental
development about the middle of the nineteenth century, and declared
a _guerre à l'outrance_ against independent science. This happened
in three important challenges to reason, for the explicitness and
resoluteness of which modern science and culture cannot but be
grateful to the "Vicar of Christ." (1) In December, 1854, the pope
promulgated the dogma of the immaculate conception of Mary. (2) Ten
years afterwards--in December, 1864--the pope published, in his
famous _encyclica_, an absolute condemnation of the whole of modern
civilization and culture; in the _syllabus_ that accompanied it he
enumerated and anathematized all the rational theses and philosophical
principles which are regarded by modern science as lucid truths. (3)
Finally, six years afterwards--on July 13, 1870--the militant head of
the Church crowned his folly by claiming _infallibility_ for himself
and all his predecessors in the papal chair. This triumph of the Roman
_curia_ was communicated to the astonished world five days afterwards,
on the very day on which France declared war with Prussia. Two months
later the temporal power of the pope was taken from him in consequence
of the war.

These three stupendous acts of the papacy were such obvious assaults on
the reason of the nineteenth century that they gave rise, from the very
beginning, to a most heated discussion even within orthodox Catholic
circles. When the Vatican Council proceeded to define the dogma of
infallibility on July 13, 1870, only three-fourths of the bishops
declared in its favor, 451 out of 601 assenting; many other bishops,
who wished to keep clear of the perilous definition, were absent from
the council. But the shrewd pontiff had calculated better than the
timid "discreet Catholics": even this extraordinary dogma was blindly
accepted by the credulous and uneducated masses of the faithful.

The whole history of the papacy, as it is substantiated by a thousand
reliable sources and accessible documents, appears to the impartial
student as an unscrupulous tissue of lying and deceit, a reckless
pursuit of absolute mental despotism and secular power, a frivolous
contradiction of all the high moral precepts which true Christianity
enunciates--charity and toleration, truth and chastity, poverty and
self-denial. When we judge the long series of popes and of the Roman
princes of the Church, from whom the pope is chosen, by the standard of
pure Christian morality, it is clear that the great majority of them
were pitiful impostors, many of them utterly worthless and vicious.
These well-known historical facts, however, do not prevent millions
of educated Catholics from admitting the infallibility which the pope
has claimed for himself; they do not prevent Protestant princes from
going to Rome, and doing reverence to the pontiff (their most dangerous
enemy); they do not prevent the fate of the German people from being
intrusted to-day to the hands of the servants and followers of this
"pious impostor" in the Reichstag--thanks to the incredible political
indolence and credulity of the nation.

The most interesting of the three great events by which the papacy has
endeavored to maintain and strengthen its despotism in the nineteenth
century is the publication of the encyclica and the syllabus in
December, 1864. In these remarkable documents all independent action
was forbidden to reason and science, and they were commanded to submit
implicitly to faith--that is, to the decrees of the infallible pope.
The great excitement which followed this sublime piece of effrontery in
educated and independent circles was in proportion with the stupendous
contents of the encyclica. Draper has given us an excellent discussion
of its educational and political significance in his _History of the
Conflict between Science and Religion_.

The dogma of the immaculate conception seems, perhaps, to be less
audacious and significant than the encyclica and the dogma of the
infallibility of the pope. Yet not only the Roman hierarchy, but
even some of the orthodox Protestants (the Evangelical Alliance, for
instance), attach great importance to this thesis. What is known
as the "immaculate oath"--that is, the confirmation of faith by an
oath taken on the immaculate conception of Mary--is still regarded by
millions of Christians as a sacred obligation. Many believers take the
dogma in a twofold application; they think that the mother of Mary was
impregnated by the Holy Ghost as well as Mary herself. Comparative and
critical theology has recently shown that this myth has no greater
claim to originality than most of the other stories in the Christian
mythology; it has been borrowed from older religions, especially
Buddhism. Similar myths were widely circulated in India, Persia,
Asia Minor, and Greece several centuries before the birth of Christ.
Whenever a king's unwedded daughter, or some other maid of high degree,
gave birth to a child, the father was always pronounced to be a god, or
a demi-god; in the Christian case it was the Holy Ghost.

The special endowments of mind or body which often distinguished these
"children of love" above ordinary offspring were thus partly explained
by "heredity." Distinguished "sons of God" of this kind were held in
high esteem both in antiquity and during the Middle Ages, while the
moral code of modern civilization reproaches them with their want of
honorable parentage. This applies even more forcibly to "daughters of
God," though the poor maidens are just as little to blame for their
want of a father. For the rest, every one who is familiar with the
beautiful mythology of classical antiquity knows that these sons and
daughters of the Greek and Roman gods often approach nearest to the
highest ideal of humanity. Recollect the large legitimate family, and
the still more numerous illegitimate offspring, of Zeus.

To return to the particular question of the impregnation of the Virgin
Mary by the Holy Ghost, we are referred to the gospels for testimony
to the fact. The only two evangelists who speak of it, Matthew and
Luke, relate in harmony that the Jewish maiden Mary was betrothed to
the carpenter Joseph, but became pregnant without his co-operation,
and, indeed, "by the Holy Ghost." As we have already related, the
four canonical gospels which are regarded as the only genuine ones
by the Christian Church, and adopted as the foundation of faith,
were deliberately chosen from a much larger number of gospels, the
details of which contradict each other sometimes just as freely as the
assertions of the four. The fathers of the Church enumerate from forty
to fifty of these spurious or apocryphal gospels; some of them are
written both in Greek and Latin--for instance, the gospel of James, of
Thomas, of Nicodemus, and so forth. The details which these apocryphal
gospels give of the life of Christ, especially with regard to his birth
and childhood, have just as much (or, on the whole, just as little)
claim to historical validity as the four canonical gospels.

Now we find in one of these documents an historical statement,
confirmed, moreover, in the _Sepher Toldoth Jeschua_, which probably
furnishes the simple and natural solution of the "world-riddle" of the
supernatural conception and birth of Christ. The author curtly gives us
in one sentence the remarkable statement which contains this solution:
"Josephus Pandera, the Roman officer of a Calabrian legion which was in
Judæa, seduced Miriam of Bethlehem, and was the father of Jesus." Other
details given about Miriam (the Hebrew name for Mary) are far from
being to the credit of the "Queen of Heaven."

Naturally, these historical details are carefully avoided by the
official theologian, but they assort badly with the traditional myth,
and lift the veil from its mystery in a very simple and natural
fashion. That makes it the more incumbent on impartial research and
pure reason to make a critical examination of these statements. It
must be admitted that they have much more title to credence than all
the other statements about the birth of Christ. When, on familiar
principles of science, we put aside the notion of supernatural
conception through an "overshadowing of the Most High" as a pure myth,
there only remains the widely accepted version of modern rational
theology--that Joseph, the Jewish carpenter, was the true father of
Christ. But this assumption is explicitly contradicted by many texts
of the gospels; Christ himself was convinced that he was a "Son of
God," and he never recognized his foster-father, Joseph, as his real
parent. Joseph, indeed, wanted to leave his betrothed when he found her
pregnant without his interference. He gave up this idea when an angel
appeared to him in a dream and pacified him. As it is expressly stated
in the first chapter of Matthew (vv. 24, 25), there was no sexual
intercourse between Joseph and Mary until after Jesus was born.

The statement of the apocryphal gospels, that the Roman officer,
Pandera, was the true father of Christ, seems all the more credible
when we make a careful anthropological study of the personality
of Christ. He is generally regarded as purely Jewish. Yet the
characteristics which distinguish his high and noble personality,
and which give a distinct impress to his religion, are certainly not
Semitical; they are rather features of the higher Arian race, and
especially of its noblest branch, the Hellenes. Now, the name of
Christ's real father, "Pandera," points unequivocally to a Greek
origin; in one manuscript, in fact, it is written "Pandora." Pandora
was, according to the Greek mythology, the first woman, born of
the earth by Vulcan and adorned with every charm by the gods, who
was espoused by Epimetheus, and sent by Zeus to men with the dread
"Pandora-box," containing every evil, in punishment for the stealing of
divine fire from heaven by Prometheus.

And it is interesting to see the different reception that the
love-story of Miriam has met with at the hands of the four great
Christian nations of civilized Europe. The stern morality of the
Teutonic races entirely repudiates it; the righteous German and the
prudish Briton prefer to believe blindly in the impossible thesis of a
conception "by the Holy Ghost." It is well known that this strenuous
and carefully paraded prudery of the higher classes (especially in
England) is by no means reflected in the true condition of sexual
morality in high quarters. The revelations which the _Pall Mall
Gazette_, for instance, made on the subject twelve years ago vividly
recalled the condition of Babylon.

The Romantic races, which ridicule this prudery and take sexual
relations less seriously, find _Mary's Romance_ attractive enough;
the special cult which "Our Lady" enjoys in France and Italy is often
associated with this love-story with curious naïveté. Thus, for
example, Paul de Regla (Dr. Desjardin), author of _Jesus of Nazareth
considered from a Scientific, Historical, and Social Standpoint_
(1894), finds precisely in the illegitimate birth of Christ a special
"title to the halo that irradiates his noble form."

It seemed to me necessary to enter fully into this important question
of the origin of Christ in the sense of impartial historical science,
because the Church militant itself lays great emphasis on it, and
because it regards the miraculous structure which has been founded
on it as one of its strongest weapons against modern thought. The
highest ethical value of pure primitive Christianity and the ennobling
influence of this "religion of love" on the history of civilization are
quite independent of those mythical dogmas. The so-called "revelations"
on which these myths are based are incompatible with the firmest
results of modern science.



    Monism as a Connecting Link between Religion and Science--The
    _Cultur-Kampf_--The Relations of Church and State--Principles
    of the Monistic Religion--Its Three-fold Ideal: the Good, the
    True, and the Beautiful--Contradiction between Scientific and
    Christian Truth--Harmony of the Monistic and the Christian Idea
    of Virtue--Opposition between Monistic and Christian Views
    of Art--Modern Expansion and Enrichment of Our Idea of the
    World--Landscape-Painting and the Modern Enjoyment of Nature--The
    Beauties of Nature--This World and Beyond--Monistic Churches

Many distinguished scientists and philosophers of the day, who share
our monistic views, consider that religion is generally played out.
Their meaning is that the clear insight into the evolution of the world
which the great scientific progress of the nineteenth century has
afforded us will satisfy, not only the causal feeling of our reason,
but even our highest emotional cravings. This view is correct in the
sense that the two ideas, religion and science, would indeed blend
into one if we had a perfectly clear and consecutive system of monism.
However, there are but a few resolute thinkers who attain to this most
pure and lofty conception of Spinoza and Goethe. Most of the educated
people of our time (as distinct from the uncultured masses) remain in
the conviction that religion is a separate branch of our mental life,
independent of science, and not less valuable and indispensable.

If we adopt this view, we can find a means of reconciling the two
great and apparently quite distinct branches in the idea I put forward
in "Monism, as a Connecting-Link between Religion and Science,"
in 1892. In the preface to this _Confession of Faith of a Man of
Science_ I expressed myself in the following words with regard to
its double object: "In the first place, I must give expression to
the rational system which is logically forced upon us by the recent
progress of science; it dwells in the intimate thoughts of nearly every
impartial and thoughtful scientist, though few have the courage or
the disposition to avow it. In the second place, I would make of it a
connecting-link between religion and science, and thus do away with
the antithesis which has been needlessly maintained between these two
branches of the highest activity of the human mind. The ethical craving
of our emotion is satisfied by monism no less than the logical demand
for causality on the part of reason."

The remarkable interest which the discourse enkindled is a proof that
in this monistic profession of faith I expressed the feeling not only
of many scientists, but of a large number of cultured men and women
of very different circles. Not only was I rewarded by hundreds of
sympathetic letters, but by a wide circulation of the printed address,
of which six editions were required within six months. I had the more
reason to be content with this unexpected success, as this "confession
of faith" was originally merely an occasional speech which I delivered
unprepared on October 9, 1892, at Altenburg, during the jubilee of the
Scientific Society of East Germany. Naturally there was the usual
demonstration on the other side; I was fiercely attacked, not only by
the ultramontane press, the sworn defenders of superstition, but also
by the "liberal" controversialists of evangelical Christianity, who
profess to defend both scientific truth and purified faith. In the
seven years that have ensued since that time the great struggle between
modern science and orthodox Christianity has become more threatening;
it has grown more dangerous for science in proportion as Christianity
has found support in an increasing mental and political reaction. In
some countries the Church has made such progress that the freedom
of thought and conscience, which is guaranteed by the laws, is in
practice gravely menaced (for instance, in Bavaria). The great historic
struggle which Draper has so admirably depicted in his _Conflict
between Religion and Science_ is to-day more acute and significant than
ever. For the last twenty-seven years it has been rightly called the

The famous encyclica and syllabus which the militant pope, Pius IX.,
sent out into the entire world in 1864 were a declaration of war on
the whole of modern science; they demanded the blind submission of
reason to the dogmas of the infallible pope. The enormity of this
crude assault on the highest treasures of civilization even roused
many indolent minds from the slumber of belief. Together with the
subsequent promulgation of the papal infallibility (1870), the
encyclica provoked a deep wave of irritation and an energetic repulse
which held out high hopes. In the new German empire, which had attained
its indispensable national unity by the heavy sacrifices of the wars
of 1866 and 1871, the insolent attacks of the pope were felt to be
particularly offensive. On the one hand, Germany is the cradle of
the Reformation and the modern emancipation of reason; on the other
hand, it unfortunately has in its 18,000,000 Catholics a vast host of
militant believers, who are unsurpassed by any other civilized people
in blind obedience to their chief shepherd.

The dangers of such a situation were clearly recognized by the
great statesman who had solved the political "world-riddle" of the
dismemberment of Germany, and had led us by a marvellous statecraft
to the long-desired goal of national unity and power. Prince Bismarck
began the famous struggle with the Vatican, which is known as the
_cultur-kampf_, in 1872, and it was conducted with equal ability and
energy by the distinguished Minister of Worship, Falk, author of the
May laws of 1873. Unfortunately, Bismarck had to desist six years
afterwards. Although the great statesman was a remarkable judge of men
and a realistic politician of immense tact, he had underestimated the
force of three powerful obstacles--first, the unsurpassed cunning and
unscrupulous treachery of the Roman _curia_; secondly, the correlative
ingratitude and credulity of the uneducated Catholic masses, on which
the papacy built; and, thirdly, the power of apathy, the continuance
of the irrational, simply because it is in possession. Hence, in 1878,
when the abler Leo XIII. had ascended the pontifical throne, the fatal
"To Canossa" was heard once more. From that time the newly established
power of Rome grew in strength; partly through the unscrupulous
intrigues and serpentine bends of its slippery Jesuitical politics,
partly through the false Church-politics of the German government and
the marvellous political incompetence of the German people. We have,
therefore, at the close of the nineteenth century to endure the
pitiful spectacle of the Catholic "Centre" being the most important
section of the Reichstag, and the fate of our humiliated country
depending on a papal party, which does not constitute numerically a
third part of the nation.

When the _cultur-kampf_ began in 1872, it was justly acclaimed by
all independent thinkers as a political renewal of the Reformation,
a vigorous attempt to free modern civilization from the yoke of
papal despotism. The whole of the Liberal press hailed Bismarck as a
"political Luther"--as the great hero, not only of the national unity,
but also of the rational emancipation of Germany. Ten years afterwards,
when the papacy had proved victorious, the same "Liberal press" changed
its colors, and denounced the _cultur-kampf_ as a great mistake; and
it does the same thing to-day. The facts show how short is the memory
of our journalists, how defective their knowledge of history, and how
poor their philosophic education. The so-called "Peace between Church
and State" is never more than a suspension of hostilities. The modern
papacy, true to the despotic principles it has followed for the last
sixteen hundred years, is determined to wield sole dominion over the
credulous souls of men; it must demand the absolute submission of
the cultured State, which, as such, defends the rights of reason and
science. True and enduring peace there cannot be until one of the
combatants lies powerless on the ground. Either the Church wins, and
then farewell to all "free science and free teaching"--then are our
universities no better than jails, and our colleges become cloistral
schools; or else the modern rational State proves victorious--then,
in the twentieth century, human culture, freedom, and prosperity will
continue their progressive development until they far surpass even the
height of the nineteenth century.

In order to compass these high aims, it is of the first importance that
modern science not only shatter the false structures of superstition
and sweep their ruins from the path, but that it also erect a new
abode for human emotion on the ground it has cleared--a "palace of
reason," in which, under the influence of our new monistic views, we do
reverence to the real trinity of the nineteenth century--the trinity of
"the true, the good, and the beautiful." In order to give a tangible
shape to the cult of this divine ideal, we must first of all compare
our position with the dominant forms of Christianity, and realize
the changes that are involved in the substitution of the one for the
other. For, in spite of its errors and defects, the Christian religion
(in its primitive and purer form) has so high an ethical value, and
has entered so deeply into the most important social and political
movements of civilized history for the last fifteen hundred years,
that we must appeal as much as possible to its existing institutions
in the establishment of our monistic religion. We do not seek a mighty
_revolution_, but a rational _reformation_, of our religious life. And
just as, two thousand years ago, the classic poetry of the ancient
Greeks incarnated their ideals of virtue in divine shapes, so may
we, too, lend the character of noble goddesses to our three rational
ideals. We must inquire into the features of the three goddesses of the
monist--truth, beauty, and virtue; and we must study their relation
to the three corresponding ideals of Christianity which they are to

I. The preceding inquiries (especially those of the first and third
sections) have convinced us that truth unadulterated is only to be
found in the temple of the study of nature, and that the only available
paths to it are critical observation and reflection--the empirical
investigation of facts and the rational study of their efficient
causes. In this way we arrive, by means of pure reason, at true
science, the highest treasure of civilized man. We must, in accordance
with the arguments of our sixteenth chapter, reject what is called
"revelation," the poetry of faith, that affirms the discovery of truth
in a supernatural fashion, without the assistance of reason. And since
the entire structure of the Judæo-Christian religion, like that of the
Mohammedan and the Buddhistic, rests on these so-called revelations,
and these mystic fruits of the imagination directly contradict the
clear results of empirical research, it is obvious that we shall
only attain to a knowledge of the truth by the rational activity of
genuine science, not by the poetic imagining of a mystic faith. In this
respect it is quite certain that the Christian system must give way
to the monistic. The goddess of truth dwells in the temple of nature,
in the green woods, on the blue sea, and on the snowy summits of the
hills--not in the gloom of the cloister, nor in the narrow prisons of
our jail-like schools, nor in the clouds of incense of the Christian
churches. The paths which lead to the noble divinity of truth and
knowledge are the loving study of nature and its laws, the observation
of the infinitely great star-world with the aid of the telescope, and
the infinitely tiny cell-world with the aid of the microscope--not
senseless ceremonies and unthinking prayers, not alms and Peter's
Pence. The rich gifts which the goddess of truth bestows on us are the
noble fruits of the tree of knowledge and the inestimable treasure of a
clear, unified view of the world--not belief in supernatural miracles
and the illusion of an eternal life.

II. It is otherwise with the divine ideal of eternal goodness. In our
search for the truth we have entirely to exclude the "revelation" of
the churches, and devote ourselves solely to the study of nature; but,
on the other hand, the idea of the good, which we call virtue, in
our monistic religion coincides for the most part with the Christian
idea of virtue. We are speaking, naturally, of the primitive and
pure Christianity of the first three centuries, as far as we learn
its moral teaching from the gospels and the epistles of Paul; it
does not apply to the Vatican caricature of that pure doctrine which
has dominated European civilization, to its infinite prejudice, for
twelve hundred years. The best part of Christian morality, to which we
firmly adhere, is represented by the humanist precepts of charity and
toleration, compassion and assistance. However, these noble commands,
which are set down as "Christian" morality (in its best sense), are by
no means original discoveries of Christianity; they are derived from
earlier religions. The Golden Rule, which sums up these precepts in
one sentence, is centuries older than Christianity. In the conduct of
life this law of natural morality has been followed just as frequently
by non-Christians and atheists as it has been neglected by pious
believers. Moreover, Christian ethics was marred by the great defect
of a narrow insistence on altruism and a denunciation of egoism. Our
monistic ethics lays equal emphasis on the two, and finds perfect
virtue in the just balance of love of self and love of one's neighbor
(cf. chap. xix.).

III. But monism enters into its strongest opposition to Christianity
on the question of beauty. Primitive Christianity preached the
worthlessness of earthly life, regarding it merely as a preparation
for an eternal life beyond. Hence it immediately followed that all we
find in the life of man here below, all that is beautiful in art and
science, in public and in private life, is of no real value. The true
Christian must avert his eyes from them; he must think only of a worthy
preparation for the life beyond. Contempt of nature, aversion from all
its inexhaustible charms, rejection of every kind of fine art, are
Christian duties; and they are carried out to perfection when a man
separates himself from his fellows, chastises his body, and spends all
his time in prayer in the cloister or the hermit's cell.

History teaches us that this ascetical morality that would scorn the
whole of nature had, as a natural consequence, the very opposite effect
to that it intended. Monasteries, the homes of chastity and discipline,
soon became dens of the wildest orgies; the sexual commerce of monks
and nuns has inspired shoals of novels, as it is so faithfully depicted
in the literature of the Renaissance. The cult of the "beautiful,"
which was then practised, was in flagrant contradiction with the
vaunted "abandonment of the world"; and the same must be said of the
pomp and luxury which soon developed in the immoral private lives of
the higher ecclesiastics and in the artistic decoration of Christian
churches and monasteries.

It may be objected that our view is refuted by the splendor of
Christian art, which, especially in the best days of the Middle Ages,
created works of undying beauty. The graceful Gothic cathedrals and
Byzantine basilicas, the hundreds of magnificent chapels, the thousands
of marble statues of saints and martyrs, the millions of fine pictures
of saints, of profoundly conceived representations of Christ and the
madonna--all are proofs of the development of a noble art in the Middle
Ages, which is unique of its kind. All these splendid monuments of
mediæval art are untouched in their high æsthetic value, whatever we
say of their mixture of truth and fancy. Yes; but what has all that
to do with the pure teaching of Christianity--with that religion of
sacrifice that turned scornfully away from all earthly parade and
glamour, from all material beauty and art; that made light of the life
of the family and the love of woman; that urged an exclusive concern as
to the immaterial goods of eternal life? The idea of a Christian art
is a contradiction in terms--a _contradictio in adjecto_. The wealthy
princes of the Church who fostered it were candidly aiming at very
different ideals, and they completely attained them. In directing the
whole interest and activity of the human mind in the Middle Ages to the
Christian Church and its distinctive art they were diverting it _from
nature_ and from the knowledge of the treasures that were hidden in it,
and would have conducted to independent science. Moreover, the daily
sight of the huge images of the saints and of the scenes of "sacred
history" continually reminded the faithful of the vast collection of
myths that the Church had made. The legends themselves were taught
and believed to be true narratives, and the stories of miracles to be
records of actual events. It cannot be doubted that in this respect
Christian art has exercised an immense influence on general culture,
and especially in the strengthening of Christian belief--an influence
which still endures throughout the entire civilized world.

The diametrical opposite of this dominant Christian art is the new
artistic tendency which has been developed during the present century
in connection with science. The remarkable expansion of our knowledge
of nature, and the discovery of countless beautiful forms of life,
which it includes, have awakened quite a new æsthetic sense in our
generation, and thus given a new tone to painting and sculpture.
Numerous scientific voyages and expeditions for the exploration
of unknown lands and seas, partly in earlier centuries, but more
especially in the nineteenth, have brought to light an undreamed
abundance of new organic forms. The number of new species of animals
and plants soon became enormous, and among them (especially among the
lower groups that had been neglected before) there were thousands
of forms of great beauty and interest, affording an entirely new
inspiration for painting, sculpture, architecture, and technical
art. In this respect a new world was revealed by the great advance
of microscopic research in the second half of the century, and
especially by the discovery of the marvellous inhabitants of the
deep sea, which were first brought to light by the famous expedition
of the _Challenger_ (1872-76). Thousands of graceful radiolaria and
thalamophora, of pretty medusæ and corals, of extraordinary molluscs,
and crabs, suddenly introduced us to a wealth of hidden organisms
beyond all anticipation, the peculiar beauty and diversity of which
far transcend all the creations of the human imagination. In the
fifty large volumes of the account of the _Challenger_ expedition a
vast number of these beautiful forms are delineated on three thousand
plates; and there are millions of other lovely organisms described in
other great works that are included in the fast-growing literature of
zoology and botany of the last ten years. I began on a small scale to
select a number of these beautiful forms for more popular description
in my _Art Forms in Nature_ (1899).

However, there is now no need for long voyages and costly works to
appreciate the beauties of this world. A man needs only to keep his
eyes open and his mind disciplined. Surrounding nature offers us
everywhere a marvellous wealth of lovely and interesting objects of all
kinds. In every bit of moss and blade of grass, in every beetle and
butterfly, we find, when we examine it carefully, beauties which are
usually overlooked. Above all, when we examine them with a powerful
glass or, better still, with a good microscope, we find everywhere in
nature a new world of inexhaustible charms.

But the nineteenth century has not only opened our eyes to the æsthetic
enjoyment of the microscopic world; it has shown us the beauty of
the greater objects in nature. Even at its commencement it was the
fashion to regard the mountains as magnificent but forbidding, and
the sea as sublime but dreaded. At its close the majority of educated
people--especially they who dwell in the great cities--are delighted
to enjoy the glories of the Alps and the crystal splendor of the
glacier world for a fortnight every year, or to drink in the majesty
of the ocean and the lovely scenery of its coasts. All these sources
of the keenest enjoyment of nature have only recently been revealed
to us in all their splendor, and the remarkable progress we have
made in facility and rapidity of conveyance has given even the less
wealthy an opportunity of approaching them. All this progress in the
æsthetic enjoyment of nature--and, proportionately, in the scientific
understanding of nature--implies an equal advance in higher mental
development and, consequently, in the direction of our monistic

The opposite character of our _naturalistic_ century to that of the
_anthropistic_ centuries that preceded is especially noticeable in
the different appreciation and spread of illustrations of the most
diverse natural objects. In our own days a lively interest in artistic
work of that kind has been developed, which did not exist in earlier
ages; it has been supported by the remarkable progress of commerce
and technical art which have facilitated a wide popularization of
such illustrations. Countless illustrated periodicals convey along
with their general information a sense of the inexhaustible beauty of
nature in all its departments. In particular, landscape-painting has
acquired an importance that surpassed all imagination. In the first
half of the century one of our greatest and most erudite scientists,
Alexander Humboldt, had pointed out that the development of modern
landscape-painting is not only of great importance as an incentive
to the study of nature and as a means of geographical description,
but that it is to be commended in other respects as a noble educative
medium. Since that time the taste for it has considerably increased.
It should be the aim at every school to teach the children to enjoy
scenery at an early age, and to give them the valuable art of
imprinting on the memory by a drawing or water-color sketch.

The infinite wealth of nature in what is beautiful and sublime offers
every man with open eyes and an æsthetic sense an incalculable sum of
choicest gifts. Still, however valuable and agreeable is the immediate
enjoyment of each single gift, its worth is doubled by a knowledge of
its meaning and its connection with the rest of nature. When Humboldt
gave us the "outline of a physical description of the world" in his
magnificent _Cosmos_ forty years ago, and when he combined scientific
and æsthetic consideration so happily in his standard _Prospects of
Nature_, he justly indicated how closely the higher enjoyment of nature
is connected with the "scientific establishment of cosmic laws," and
that the conjunction of the two serves to raise human nature to a
higher stage of perfection. The astonishment with which we gaze upon
the starry heavens and the microscopic life in a drop of water, the awe
with which we trace the marvellous working of energy in the motion of
matter, the reverence with which we grasp the universal dominance of
the law of substance throughout the universe--all these are part of our
emotional life, falling under the heading of "natural religion."

This progress of modern times in knowledge of the true and enjoyment
of the beautiful expresses, on the one hand, a valuable element of our
monistic religion, but is, on the other hand, in fatal opposition to
Christianity. For the human mind is thus made to live on this side of
the grave; Christianity would have it ever gaze beyond. Monism teaches
that we are perishable children of the earth, who for one or two,
or, at the most, three generations, have the good fortune to enjoy
the treasures of our planet, to drink of the inexhaustible fountain
of its beauty, and to trace out the marvellous play of its forces.
Christianity would teach us that the earth is "a vale of tears," in
which we have but a brief period to chasten and torment ourselves in
order to merit the life of eternal bliss beyond. Where this "beyond"
is, and of what joys the glory of this eternal life is compacted, no
revelation has ever told us. As long as "heaven" was thought to be the
blue vault that hovers over the disk of our planet, and is illumined
by the twinkling light of a few thousand stars, the human imagination
could picture to itself the ambrosial banquets of the Olympic gods
above or the laden tables of the happy dwellers in Valhalla. But now
all these deities and the immortal souls that sat at their tables are
"houseless and homeless," as David Strauss has so ably described; for
we know from astrophysical science that the immeasurable depths of
space are filled with a prosaic ether, and that millions of heavenly
bodies, ruled by eternal laws of iron, rush hither and thither in the
great ocean, in their eternal rhythm of life and death.

The places of devotion, in which men seek the satisfaction of their
religious emotions and worship the objects of their reverence, are
regarded as sacred "churches." The pagodas of Buddhistic Asia, the
Greek temples of classical antiquity, the synagogues of Palestine,
the mosques of Egypt, the Catholic cathedrals of the south, and the
Protestant cathedrals of the north, of Europe--all these "houses of
God" serve to raise man above the misery and the prose of daily life,
to lift him into the sacred, poetic atmosphere of a higher, ideal
world. They attain this end in a thousand different ways, according
to their various forms of worship and their age. The modern man who
"has science and art"--and, therefore, "religion"--needs no special
church, no narrow, enclosed portion of space. For through the length
and breadth of free nature, wherever he turns his gaze, to the whole
universe or to any single part of it, he finds, indeed, the grim
"struggle for life," but by its side are ever "the good, the true, and
the beautiful"; his church is commensurate with the whole of glorious
nature. Still, there will always be men of special temperament who will
desire to have decorated temples or churches as places of devotion
to which they may withdraw. Just as the Catholics had to relinquish a
number of churches to the Reformation in the sixteenth century, so a
still larger number will pass over to "free societies" of monists in
the coming years.



    Monistic and Dualistic Ethics--Contradiction of Pure and
    Practical Reason in Kant--His Categorical Imperative--The
    Neo-Kantians--Herbert Spencer--Egoism and Altruism--Equivalence
    of the Two Instincts--The Fundamental Law of Ethics: the Golden
    Rule--Its Antiquity--Christian Ethics--Contempt of Self, the
    Body, Nature, Civilization, the Family, Woman--Roman Catholic
    Ethics--Immoral Results of Celibacy--Necessity for the Abolition of
    the Law of Celibacy, Oral Confession, and Indulgences--State and
    Church--Religion a Private Concern--Church and School--State and
    School--Need of School Reform

The practical conduct of life makes a number of definite ethical claims
on a man which can only be duly and naturally satisfied when they are
in complete harmony with his view of the world. In accordance with this
fundamental principle of our monistic philosophy, our whole system of
ethics must be rationally connected with the unified conception of the
cosmos which we have formed by our advanced knowledge of the laws of
nature. Just as the infinite universe is one great whole in the light
of our monistic teaching, so the spiritual and moral life of man is
a part of this cosmos, and our naturalistic ordering of it must also
be monistic. There are not two different, separate worlds--the one
physical and material, and the other moral and immaterial.

The great majority of philosophers and theologians still hold the
contrary opinion. They affirm, with Kant, that the moral world is quite
independent of the physical, and is subject to very different laws;
hence a man's conscience, as the basis of his moral life, must also be
quite independent of our scientific knowledge of the world, and must be
based rather on his religious faith. On that theory the study of the
moral world belongs to _practical_ reason, while that of nature, or of
the physical world, is referred to _pure_ or theoretical reason. This
unequivocal and conscious dualism of Kant's philosophy was its greatest
defect; it has caused, and still causes, incalculable mischief. First
of all the "critical Kant" had built up the splendid and marvellous
palace of pure reason, and convincingly proved that the three great
central dogmas of metaphysics--a personal God, free will, and the
immortal soul--had no place whatever in it, and that no rational proof
could be found of their reality. Afterwards, however, the "dogmatic
Kant" superimposed on this true crystal palace of _pure_ reason the
glittering, ideal castle in the air of _practical_ reason, in which
three imposing church-naves were designed for the accommodation of
those three great mystic divinities. When they had been put out at the
front door by rational knowledge they returned by the back door under
the guidance of irrational faith.

The cupola of his great cathedral of faith was crowned by Kant with his
curious idol, the famous "categorical imperative." According to it,
the demand of the universal moral law is unconditional, independent of
any regard to actuality or potentiality. It runs: "Act at all times in
such wise that the maxim (or the subjective law of thy will) may hold
good as a principle of a universal law." On that theory all normal men
would have the same sense of duty. Modern anthropology has ruthlessly
dissipated that pretty dream; it has shown that conceptions of duty
differ even more among uncivilized than among civilized nations. All
the actions and customs which we regard as sins or loathsome crimes
(theft, fraud, murder, adultery, etc.) are considered by other nations
in certain circumstances to be virtues, or even sacred duties.

Although the obvious contradiction of the two forms of reason in Kant's
teaching, the fundamental antagonism of pure and practical reason, was
recognized and attacked at the very beginning of the century, it is
still pretty widely accepted. The modern school of neo-Kantians urges a
"return to Kant" so pressingly precisely on account of this agreeable
dualism; the Church militant zealously supports it because it fits
in admirably with its own mystic faith. But it met with an effective
reverse at the hands of modern science in the second half of the
nineteenth century, which entirely demolished the theses of the system
of practical reason. Monistic cosmology proved, on the basis of the law
of substance, that there is no personal God; comparative and genetic
psychology showed that there cannot be an immortal soul; and monistic
physiology proved the futility of the assumption of "free will."
Finally, the science of evolution made it clear that the same eternal
iron laws that rule in the inorganic world are valid too in the organic
and moral world.

But modern science gives not only a negative support to practical
philosophy and ethics in demolishing the Kantian dualism, but it
renders the positive service of substituting for it the new structure
of ethical monism. It shows that the feeling of duty does not rest
on an illusory "categorical imperative," but on the solid ground of
_social instinct_, as we find in the case of all social animals. It
regards as the highest aim of all morality the re-establishment of a
sound harmony between egoism and altruism, between self-love and the
love of one's neighbor. It is to the great English philosopher, Herbert
Spencer, that we owe the founding of this monistic ethics on a basis of

Man belongs to the social vertebrates, and has, therefore, like all
social animals, two sets of duties--first to himself, and secondly
to the society to which he belongs. The former are the behests of
self-love or egoism, the latter of love for one's fellows or altruism.
The two sets of precepts are equally just, equally natural, and equally
indispensable. If a man desire to have the advantage of living in an
organized community, he has to consult not only his own fortune, but
also that of the society, and of the "neighbors" who form the society.
He must realize that its prosperity is his own prosperity, and that it
cannot suffer without his own injury. This fundamental law of society
is so simple and so inevitable that one cannot understand how it can be
contradicted in theory or in practice; yet that is done to-day, and has
been done for thousands of years.

The equal appreciation of these two natural impulses, or the moral
equivalence of self-love and love of others, is the chief and the
fundamental principle of our morality. Hence the highest aim of all
ethics is very simple--it is the re-establishment of "the natural
equality of egoism and altruism, of the love of one's self and the
love of one's neighbor." The Golden Rule says: "Do unto others as you
would that they should do unto you." From this highest precept of
Christianity it follows of itself that we have just as sacred duties
towards ourselves as we have towards our fellows. I have explained
my conception of this principle in my _Monism_, and laid down three
important theses. (1) Both these concurrent impulses are natural
laws, of equal importance and necessity for the preservation of the
family and the society; egoism secures the self-preservation of the
individual, altruism that of the species which is made up of the chain
of perishable individuals. (2) The social duties which are imposed
by the social structure of the associated individuals, and by means
of which it secures its preservation, are merely higher evolutionary
stages of the social instincts, which we find in all higher social
animals (as "habits which have become hereditary"). (3) In the case of
civilized man all ethics, theoretical or practical, being "a science
of rules," is connected with his view of the world at large, and
consequently with his religion.

From the recognition of the fundamental principle of our morality
we may immediately deduce its highest precept, that noble command,
which is often called the Golden Rule of morals, or, briefly, the
Golden Rule. Christ repeatedly expressed it in the simple phrase:
"Thou shalt love thy neighbor as thyself." Mark adds that "there is
no greater commandment than this," and Matthew says: "In these two
commandments is the whole law and the prophets." In this greatest and
highest commandment our monistic ethics is completely at one with
Christianity. We must, however, recall the historical fact that the
formulation of this supreme command is not an original merit of Christ,
as the majority of Christian theologians affirm and their uncritical
supporters blindly accept. The Golden Rule is five hundred years
older than Christ; it was laid down as the highest moral principle by
many Greek and Oriental sages. Pittacus, of Mylene, one of the seven
wise men of Greece, said six hundred and twenty years before Christ:
"Do not that to thy neighbor that thou wouldst not suffer from him."
Confucius, the great Chinese philosopher and religious founder (who
rejected the idea of a personal God and of the immortality of the
soul), said five hundred years B.C.: "Do to every man as thou wouldst
have him do to thee; and do not to another what thou wouldst not have
him do to thee. This precept only dost thou need; it is the foundation
of all other commandments." Aristotle taught about the middle of the
fourth century B.C.: "We must act towards others as we wish others
to act towards us." In the same sense, and partly in the same words,
the Golden Rule was given by Thales, Isocrates, Aristippus, Sextus,
the Pythagorean, and other philosophers of classic antiquity--several
centuries before Christ. From this collection it is clear that the
Golden Rule had a _polyphyletic_ origin--that is, it was formulated by
a number of philosophers at different times and in different places,
quite independently of each other. Otherwise it must be assumed that
Jesus derived it from some other Oriental source, from ancient Semitic,
Indian, Chinese, or especially Buddhistic traditions, as has been
proved in the case of most of the other Christian doctrines.

As the great ethical principle is thus twenty-five hundred years old,
and as Christianity itself has put it at the head of its moral teaching
as the highest and all-embracing commandment, it follows that our
monistic ethics is in complete harmony on this important point, not
only with the ethics of the ancient heathens, but also with that of
Christianity. Unfortunately this harmony is disturbed by the fact that
the gospels and the Pauline epistles contain many other points of moral
teaching, which contradict our first and supreme commandment. Christian
theologians have fruitlessly striven to explain away these striking
and painful contradictions by their ingenious interpretations. We need
not enter into that question now, but we must briefly consider those
unfortunate aspects of Christian ethics which are incompatible with the
better thought of the modern age, and which are distinctly injurious
in their practical consequences. Of that character is the contempt
which Christianity has shown for self, for the body, for nature, for
civilization, for the family, and for woman.

I. The supreme mistake of Christian ethics, and one which runs
directly counter to the Golden Rule, is its exaggeration of love of
one's neighbor at the expense of self-love. Christianity attacks and
despises egoism on principle. Yet that natural impulse is absolutely
indispensable in view of self-preservation; indeed, one may say that
even altruism, its apparent opposite, is only an enlightened egoism.
Nothing great or elevated has ever taken place without egoism, and
without the passion that urges us to great sacrifices. It is only
the excesses of the impulse that are injurious. One of the Christian
precepts that were impressed upon us in our early youth as of great
importance, and that are glorified in millions of sermons, is: "Love
your enemies, bless them that curse you, do good to them that hate you,
and pray for them which despitefully use you and persecute you." It is
a very ideal precept, but as useless in practice as it is unnatural.
So it is with the counsel, "If any man will take away thy coat, let
him have thy cloak also." Translated into the terms of modern life,
that means: "When some unscrupulous scoundrel has defrauded thee of
half thy goods, let him have the other half also." Or, again, in the
language of modern politics: "When the pious English take from you
simple Germans one after another of your new and valuable colonies in
Africa, let them have all the rest of your colonies also--or, best of
all, give them Germany itself." And, while we touch on the marvellous
world-politics of modern England, we may note in passing its direct
contradiction of every precept of Christian charity, which is more
frequently on the lips of that great nation than of any other nation in
the world. However, the glaring contradiction between the theoretical,
_ideal_, altruistic morality of the human individual and the _real_,
purely selfish morality of the human community, and especially of the
civilized Christian state, is a familiar fact. It would be interesting
to determine mathematically in what proportion among organized men the
altruistic ethical ideal of the individual changes into its contrary,
the purely egoistic "real politics" of the state and the nation.

II. Since the Christian faith takes a wholly dualistic view of the
human organism and attributes to the immortal soul only a temporary
sojourn in the mortal frame, it very naturally sets a much greater
value on the soul than on the body. Hence results that neglect of the
care of the body, of training, and of cleanliness which contrasts the
life of the Christian Middle Ages so unfavorably with that of pagan
classical antiquity. Christian ethics contains none of those firm
commands as to daily ablutions which are theoretically laid down and
practically fulfilled in the Mohammedan, Hindoo, and other religions.
In many monasteries the ideal of the pious Christian is the man who
does not wash and clothe himself properly, who never changes his
malodorous gown, and who, instead of regular work, fills up his useless
life with mechanical prayers, senseless fasts, and so forth. As a
special outgrowth of this contempt of the body we have the disgusting
discipline of the flagellants and other ascetics.

III. One source of countless theoretical errors and practical
blemishes, of deplorable crudity and privation, is found in the false
anthropism of Christianity--that is, in the unique position which
it gives to man, as the image of God, in opposition to all the rest
of nature. In this way it has contributed, not only to an extremely
injurious isolation from our glorious mother "nature," but also to
a regrettable contempt of all other organisms. Christianity has no
place for that well-known love of animals, that sympathy with the
nearly related and friendly mammals (dogs, horses, cattle, etc.),
which is urged in the ethical teaching of many of the older religions,
especially Buddhism. Whoever has spent much time in the south of Europe
must have often witnessed those frightful sufferings of animals which
fill us friends of animals with the deepest sympathy and indignation.
And when one expostulates with these brutal "Christians" on their
cruelty, the only answer is, with a laugh: "But the beasts are not
Christians." Unfortunately Descartes gave some support to the error in
teaching that man only has a sensitive soul, not the animal.

How much more elevated is our monistic ethics than the Christian in
this regard! Darwinism teaches us that we have descended immediately
from the primates, and, in a secondary degree, from a long series
of earlier mammals, and that, therefore, they are "our brothers";
physiology informs us that they have the same nerves and sense-organs
as we, and the same feelings of pleasure and pain. No sympathetic
monistic scientist would ever be guilty of that brutal treatment of
animals which comes so lightly to the Christian in his anthropistic
illusion--to the "child of the God of love." Moreover, this Christian
contempt of nature on principle deprives man of an abundance of the
highest earthly joys, especially of the keen, ennobling enjoyment of

IV. Since, according to Christ's teaching, our planet is "a vale of
tears," and our earthly life is valueless and a mere preparation for a
better life to come, it has succeeded in inducing men to sacrifice all
happiness on this side of eternity and make light of all earthly goods.
Among these "earthly goods," in the case of the modern civilized man,
we must include the countless great and small conveniences of technical
science, hygiene, commerce, etc., which have made modern life cheerful
and comfortable; we must include all the gratifications of painting,
sculpture, music, and poetry, which flourished exceedingly even during
the Middle Ages (in spite of its principles), and which we esteem
as "ideal pleasures"; we must include all that invaluable progress
of science, especially the study of nature, of which the nineteenth
century is justly proud. All these "earthly goods," that have so high a
value in the eyes of the monist, are worthless--nay, injurious--for the
most part, according to Christian teaching; the stern code of Christian
morals should look just as unfavorably on the pursuit of these
pleasures as our humanistic ethics fosters and encourages it. Once
more, therefore, Christianity is found to be an enemy to civilization,
and the struggle which modern thought and science are compelled to
conduct with it is, in this additional sense, a "_cultur-kampf_."

V. Another of the most deplorable aspects of Christian morality is
its belittlement of the life of the family, of that natural living
together with our next of kin which is just as necessary in the case
of man as in the case of all the higher social animals. The family
is justly regarded as the "foundation of society," and the healthy
life of the family is a necessary condition of the prosperity of the
State. Christ, however, was of a very different opinion: with his gaze
ever directed to "the beyond," he thought as lightly of woman and the
family as of all other goods of "this life." Of his infrequent contact
with his parents and sisters the gospels have very little to say; but
they are far from representing his relations with his mother to have
been so tender and intimate as they are poetically depicted in so many
thousands of pictures. He was not married himself. Sexual love, the
first foundation of the family union, seems to have been regarded by
Jesus as a necessary evil. His most enthusiastic apostle, Paul, went
still farther in the same direction, declaring it to be better not to
marry than to marry: "It is good for a man not to touch a woman." If
humanity were to follow this excellent counsel, it would soon be rid
of all earthly misery and suffering: it would be killed off by such a
"radical cure" within half a century.

VI. As Christ never knew the love of woman, he had no personal
acquaintance with that refining of man's true nature that comes only
from the intimate life of man with woman. The intimate sexual union, on
which the preservation of the human race depends, is just as important
on that account as the spiritual penetration of the two sexes, or
the mutual complement which they bring to each other in the practical
wants of daily life as well as in the highest ideal functions of the
soul. For man and woman are two different organisms, equal in worth,
each having its characteristic virtues and defects. As civilization
advanced, this ideal value of sexual love was more appreciated, and
woman held in higher honor, especially among the Teutonic races; she
is the inspiring source of the highest achievements of art and poetry.
But Christ was as far from this view as nearly the whole of antiquity;
he shared the idea that prevailed everywhere in the East--that
woman is subordinate to man, and intercourse with her is "unclean."
Long-suffering nature has taken a fearful revenge for this blunder; its
sad consequences are written in letters of blood in the history of the
papal Middle Ages.

The marvellous hierarchy of the Roman Church, that never disdained any
means of strengthening its spiritual despotism, found an exceptionally
powerful instrument in the manipulation of this "unclean" idea, and in
the promotion of the ascetic notion that abstinence from intercourse
with women is a virtue of itself. In the first few centuries after
Christ a number of priests voluntarily abstained from marriage, and
the supposed value of this celibacy soon rose to such a degree that it
was made obligatory. In the Middle Ages the seduction of women of good
repute and of their daughters by Catholic priests (the confessional
was an active agency in the business) was a public scandal: many
communities, in order to prevent such things, pressed for a license
of concubinage to be given to the clergy. And it was done in many,
and sometimes very romantic, ways. Thus, for instance, the canon law
that the priest's cook should not be less than forty years old was
very cleverly "explained" in the sense that the priest might have two
cooks, one in the presbytery, another without; if one was twenty-four
and the other eighteen, that made forty-two together--two years above
the prescribed age. At the Christian councils, at which heretics were
burned alive, the cardinals and bishops sat down with whole troops
of prostitutes. The private and public debauchery of the Catholic
clergy was so scandalous and dangerous to the commonwealth that there
was a general rebellion against it before the time of Luther, and a
loud demand for a "reformation of the church in head and members." It
is well known that these immoral relations still continue in Roman
Catholic lands, although more in secret. Formerly proposals were
made from time to time for the definitive abrogation of celibacy, as
was done, for instance, in the chambers of Baden, Bavaria, Hesse,
Saxony, and other lands; but they have, unfortunately, hitherto proved
unavailing. In the German Reichstag, in which the ultramontane Centre
is now proposing the most ridiculous measures for the suppression of
sexual immorality, there is now no party that will urge the abolition
of celibacy in the interest of public morality. The so-called
"Freethought" Party and the utopian social democracy coquette with the
favor of the Centre.

The modern state that would lift not only the material, but the moral,
life of its people to a higher level is entitled, and indeed bound,
to sweep away such unworthy and harmful conditions. The obligatory
celibacy of the Catholic clergy is as pernicious and immoral as the
practice of auricular confession or the sale of indulgences. All
three have nothing whatever to do with primitive Christianity. All
three are directly opposed to true Christian morality. All three are
disreputable inventions of the papacy, designed for the sole purpose of
strengthening its despotic rule over the credulous masses and making as
much material profit as possible out of them.

The Nemesis of history will sooner or later exact a terrible account
of the Roman papacy, and the millions who have been robbed of their
happiness by this degenerate religion will help to give it its
death-blow in the coming twentieth century--at least, in every truly
civilized state. It has been recently calculated that the number of
men who lost their lives in the papal persecutions of heretics, the
Inquisition, the Christian religious wars, etc., is much more than
ten millions. But what is this in comparison with the tenfold greater
number of the unfortunate _moral_ victims of the institutions and
the priestly domination of the degenerate Christian Church--with the
unnumbered millions whose higher mental life was extinguished, whose
conscience was tortured, whose family life was destroyed, by the
Church? We may with truth apply the words of Goethe in his _Bride of

    "Victims fall, nor lambs nor bulls,
    But human victims numberless."

In the great _cultur-kampf_, which must go on as long as these sad
conditions exist, the first aim must be the absolute separation of
Church and State. There shall be "a free Church in a free State"--that
is, every Church shall be free in the practice of its special worship
and ceremonies, and in the construction of its fantastic poetry and
superstitious dogmas--with the sole condition that they contain no
danger to social order or morality. Then there will be equal rights
for all. Free societies and monistic religious bodies shall be equally
tolerated, and just as free in their movements as Liberal Protestant
and orthodox ultramontane congregations. But for all these "faithful"
of the most diverse sects religion will have to be a private concern.
The state shall supervise them, and prevent excesses; but it must
neither oppress nor support them. Above all, the ratepayers shall not
be compelled to contribute to the support and spread of a "faith" which
they honestly believe to be a harmful superstition. In the United
States such a complete separation of Church and State has been long
accomplished, greatly to the satisfaction of all parties. They have
also the equally important separation of the Church from the school;
that is, undoubtedly, a powerful element in the great advance which
science and culture have recently made in America.

It goes without saying that this exclusion of the Church from the
school only refers to its sectarian principles, the particular form
of belief which each Church has evolved in the course of its life.
This sectarian education is purely a private concern, and should be
left to parents and tutors, or to such priests or teachers as may
have the personal confidence of the parents. Instead of the rejected
sectarian instruction, two important branches of education will be
introduced--monistic or humanist ethics and comparative religion.
During the last thirty years an extensive literature has appeared
dealing with the new system of ethics which has been raised on the
basis of modern science--especially evolutionary science. Comparative
religion will be a natural companion to the actual elementary
instruction in "biblical history" and in the mythology of Greece and
Rome. Both of these will remain in the curriculum. The reason for
that is obvious enough; the whole of our painting and sculpture, the
chief branches of monistic æsthetics, are intimately blended with
the Christian, Greek, and Roman mythologies. There will only be this
important difference--that the Christian myths and legends will not
be taught as truths, but as poetic fancies, like the Greek and Roman
myths; the high value of the ethical and æsthetical material they
contain will not be lessened, but increased, by this means. As regards
the Bible, the "book of books" will only be given to the children in
carefully selected extracts (a sort of "school Bible"); in this way we
shall avoid the besmirching of the child's imagination with the unclean
stories and passages which are so numerous in the Old Testament.

Once the modern State has freed itself and its schools from the
fetters of the Church, it will be able to devote more attention to the
improvement of education. The incalculable value of a good system of
education has forced itself more and more upon us as the many aspects
of modern civilized life have been enlarged and enriched in the
course of the century. But the development of the educational methods
has by no means kept pace with life in general. The necessity for a
comprehensive reform of our schools is making itself felt more and
more. On this question, too, a number of valuable works have appeared
in the course of the last forty years. We shall restrict ourselves to
making a few general observations which we think of special importance.

1. In all education up to the present time _man_ has played the chief
part, and especially the grammatical study of his language; the study
of _nature_ was entirely neglected.

2. In the school of the future nature will be the chief object of the
study; a man shall learn a correct view of the world he lives in; he
will not be made to stand outside of and opposed to nature, but be
represented as its highest and noblest product.

3. The study of the classical tongues (Latin and Greek), which has
hitherto absorbed most of the pupils' time and energy, is indeed
valuable; but it will be much restricted, and confined to the mere
elements (obligatory for Latin, optional for Greek).

4. In consequence, modern languages must be all the more cultivated in
all the higher schools (English and French to be obligatory, Italian

5. Historical instruction must pay more attention to the inner
mental and spiritual life of a nation, and to the development of its
civilization, and less to its external history (the vicissitudes of
dynasties, wars, and so forth).

6. The elements of evolutionary science must be learned in conjunction
with cosmology, geology must go with geography, and anthropology with

7. The first principles of biology must be familiar to every educated
man; the modern training in observation furnishes an attractive
introduction to the biological sciences (anthropology, zoology, and
botany). A start must be made with descriptive system (in conjunction
with ætiology or bionomy); the elements of anatomy and physiology to be
added later on.

8. The first principles of physics and chemistry must also be taught,
and their exact establishment with the aid of mathematics.

9. Every pupil must be taught to draw well, and from nature; and,
wherever it is possible, the use of water-colors. The execution of
drawings and of water-color sketches from nature (of flowers, animals,
landscapes, clouds, etc.) not only excites interest in nature and helps
memory to enjoy objects, but it gives the pupil his first lesson in
_seeing_ correctly and understanding what he has seen.

10. Much more care and time must be devoted than has been done hitherto
to corporal exercise, to gymnastics and swimming; but it is especially
important to have walks in common every week, and journeys on foot
during the holidays. The lesson in observation which they obtain in
this way is invaluable.

The chief aim of higher education up to the present time, in most
countries, has been a preparation for the subsequent profession, and
the acquisition of a certain amount of information and direction
for civic duties. The school of the twentieth century will have for
its main object the formation of independent thought, the clear
understanding of the knowledge acquired, and an insight into the
natural connection of phenomena. If the modern state gives every
citizen a vote, it should also give him the means of developing his
reason by a proper education, in order to make a rational use of his
vote for the commonweal.



    A Glance at the Progress of the Nineteenth Century in Solving
    Cosmic Problems--I. Progress of Astronomy and Cosmology--Physical
    and Chemical Unity of the Universe--Cosmic Metamorphoses--Evolution
    of the Planetary System--Analogy of the Phylogenetic Processes
    on the Earth and on Other Planets--Organic Inhabitants of
    Other Heavenly Bodies--Periodic Variation in the Making of
    Worlds--II. Progress of Geology and Palæontology--Neptunism and
    Vulcanism--Theory of Continuity--III. Progress of Physics and
    Chemistry--IV. Progress of Biology--Cellular Theory and Theory of
    Descent--V. Anthropology--Origin of Man--General Conclusion

At the close of our philosophic study of the riddles of the universe
we turn with confidence to the answer to the momentous question, How
nearly have we approached to a solution of them? What is the value of
the immense progress which the passing nineteenth century has made in
the knowledge of nature? And what prospect does it open out to us for
the future, for the further development of our system in the twentieth
century, at the threshold of which we pause? Every unprejudiced thinker
who impartially considers the solid progress of our empirical science,
and the unity and clearness of our philosophic interpretation of it,
will share our view: the nineteenth century has made greater progress
in knowledge of the world and in grasp of its nature than all its
predecessors; it has solved many great problems that seemed insoluble a
hundred years ago; it has opened out to us new provinces of learning,
the very existence of which was unsuspected at the beginning of the
century. Above all, it has put clearly before our eyes the lofty aim of
monistic cosmology, and has pointed out the path which alone will lead
us towards it--the way of the exact empirical investigation of facts,
and of the critical genetic study of their causes. The great abstract
law of mechanical causality, of which our cosmological law--the law
of substance--is but another and a concrete expression, now rules
the entire universe, as it does the mind of man; it is the steady,
immovable pole-star, whose clear light falls on our path through the
dark labyrinth of the countless separate phenomena. To see the truth
of this more clearly, let us cast a brief glance at the astonishing
progress which the chief branches of science have made in this
remarkable period.


The study of the heavens is the oldest, the study of man the youngest,
of the sciences. With regard to himself and the character of his being
man only obtained a clear knowledge in the second half of the present
century; with regard to the starry heavens, the motions of the planets,
and so on, he had acquired astonishing information forty-five hundred
years ago. The ancient Chinese, Hindoos, Egyptians, and Chaldæans in
the distant East knew more of the science of the spheres than the
majority of educated Christians did in the West four thousand years
after them. An eclipse of the sun was astronomically observed in China
in the year 2697 B.C., and the plane of the ecliptic was determined
by means of a gnome eleven hundred years B.C., while Christ himself
had no knowledge whatever of astronomy--indeed, he looked out upon
heaven and earth, nature and man, from the very narrowest geocentric
and anthropocentric point of view. The greatest advance of astronomy
is generally, and rightly, said to be the founding of the heliocentric
system of Copernicus, whose famous work, _De Revolutionibus Orbium
Celestium_, of itself caused a profound revolution in the minds of
thoughtful men. In overthrowing the Ptolemaic system, he destroyed the
foundation of the Christian theory, which regarded the earth as the
centre of the universe and man as the godlike ruler of the earth. It
was natural, therefore, that the Christian clergy, with the pope at its
head, should enter upon a fierce struggle with the invaluable discovery
of Copernicus. Yet it soon cleared a path for itself, when Kepler and
Galileo grounded on it their true "mechanics of the heavens," and
Newton gave it a solid foundation by his theory of gravitation (1686).

A further great advance, comprehending the entire universe, was the
application of the idea of evolution to astronomy. It was done by
the youthful Kant in 1755; in his famous general natural history and
theory of the heavens he undertook the discussion, not only of the
"constitution," but also of the "mechanical origin" of the whole
world-structure on Newtonian principles. The splendid _Système du
Monde_ of Laplace, who had independently come to the same conclusions
as Kant on the world-problem, gave so firm a basis to this new
_Mécanique Céleste_ in 1796 that it looked as if nothing entirely
new of equal importance was left to be discovered in the nineteenth
century. Yet here again it had the honor of opening out entirely
new paths and infinitely enlarging our outlook on the universe. The
invention of photography and photometry, and especially of spectral
analysis (in 1860 by Bunsen and Kirchoff), introduced physics and
chemistry into astronomy and led to cosmological conclusions of the
utmost importance. It was now made perfectly clear that matter is
the same throughout the universe, and that its physical and chemical
properties in the most distant stars do not differ from those of the
earth under our feet.

The monistic conviction, which we thus arrived at, of the physical
and chemical unity of the entire cosmos is certainly one of the most
valuable general truths which we owe to astrophysics, the new branch
of astronomy which is honorably associated with the name of Friedrich
Zöllner. Not less important is the clear knowledge we have obtained
that the same laws of mechanical development that we have on the
earth rule throughout the infinite universe. A vast, all-embracing
metamorphosis goes on continuously in all parts of the universe,
just as it is found in the geological history of the earth; it can
be traced in the evolution of its living inhabitants as surely as in
the history of peoples or in the life of each human individual. In
one part of space we perceive, with the aid of our best telescopes,
vast nebulæ of glowing, infinitely attenuated gas; we see in them the
embryos of heavenly bodies, billions of miles away, in the first stage
of their development. In some of these "stellar embryos" the chemical
elements do not seem to be differentiated yet, but still buried in the
homogeneous primitive matter (_prothyl_) at an enormous temperature
(calculated to run into millions of degrees); it is possible that the
original basic "substance" (_vide_ p. 229) is not yet divided into
ponderable and imponderable matter. In other parts of space we find
stars that have cooled down into glowing fluid, and yet others that
are cold and rigid; we can tell their stage of evolution approximately
by their color. We find stars that are surrounded with rings and moons
like Saturn; and we recognize in the luminous ring of the nebula the
embryo of a new moon, which has detached itself from the mother-planet,
just as the planet was released from the sun.

Many of the stars, the light of which has taken thousands of years to
reach us, are certainly suns like our own mother-sun, and are girt
about with planets and moons, just as in our own solar system. We
are justified in supposing that thousands of these planets are in a
similar stage of development to that of our earth--that is, they have
arrived at a period when the temperature at the surface lies between
the freezing and boiling point of water, and so permits the existence
of water in its liquid condition. That makes it possible that carbon
has entered into the same complex combinations on those planets as
it has done on our earth, and that from its nitrogenous compounds
protoplasm has been evolved--that wonderful substance which alone,
as far as our knowledge goes, is the possessor of organic life. The
monera (for instance, chromacea and bacteria), which consist only of
this primitive protoplasm, and which arise by spontaneous generation
from these inorganic nitrocarbonates, may thus have entered upon the
same course of evolution on many other planets as on our own; first of
all, living cells of the simplest character would be formed from their
homogeneous protoplasmic body by the separation of an inner nucleus
from the outer cell body (cytostoma). Further, the analogy that we
find in the life of all cells--whether plasmodomous plant-cells or
plasmophagous animal-cells--justifies the inference that the further
course of organic evolution on these other planets has been analogous
to that of our own earth--always, of course, given the same limits of
temperature which permit water in a liquid form. In the glowing liquid
bodies of the stars, where water can only exist in the form of steam,
and on the cold extinct suns, where it can only be in the shape of ice,
such organic life as we know is impossible.

The similarity of phylogeny, or the analogy of organic evolution,
which we may thus assume in many stars which are at the same stage of
biogenetic development, naturally opens out a wide field of brilliant
speculation to the constructive imagination. A favorite subject for
such speculation has long been the question whether there are men, or
living beings like ourselves, perhaps much more highly developed, in
other planets? Among the many works which have sought to answer the
question, those of Camille Flammarion, the Parisian astronomer, have
recently been extremely popular; they are equally distinguished by
exuberant imagination and brilliant style, and by a deplorable lack
of critical judgment and biological knowledge. We may condense in the
following thesis the present condition of our knowledge on the subject:

I. It is very probable that a similar biogenetic process to that of our
own earth is taking place on some of the other planets of our solar
system (Mars and Venus), and on many planets of other solar systems;
first simple monera are formed by spontaneous generation, and from
these arise unicellular protists (first plasmodomous primitive plants,
and then plasmophagous primitive animals).

II. It is very probable that from these unicellular protists arise,
in the further course of evolution, first social cell-communities
(coenobia), and subsequently tissue-forming plants and animals
(metaphyta and metazoa).

III. It is also very probable that thallophyta (algæ and fungi) were
the first to appear in the plant-kingdom, then diaphyta (mosses and
ferns), finally anthophyta (gymnosperm and angiosperm flowering plants).

IV. It is equally probable that the biogenetic process took a similar
course in the animal kingdom--that from the blastæads (catallacta)
first gastræads were formed, and from these lower animal forms
(coelenteria) higher organisms (coelomaria) were afterwards evolved.

V. On the other hand, it is very questionable whether the different
stems of these higher animals (and those of the higher plants as well)
run through the same course of development on other planets as on our

VI. In particular, it is wholly uncertain whether there are vertebrates
on other planets, and whether, in the course of their phyletic
development, taking millions of years, mammals are formed as on earth,
reaching their highest point in the formation of man; in such an event,
millions of changes would have to be just the same in both cases.

VII. It is much more probable, on the contrary, that other planets
have produced other types of the higher plants and animals, which are
unknown on our earth; perhaps from some higher animal stem, which is
superior to the vertebrate in formation, higher beings have arisen who
far transcend us earthly men in intelligence.

VIII. The possibility of our ever entering into direct communication
with such inhabitants of other planets seems to be excluded by the
immense distance of our earth from the other heavenly bodies, and the
absence of the requisite atmosphere in the intervening space, which
contains only ether.

But while many of the stars are probably in a similar stage of
biogenetic development to that of our earth (for the last one hundred
million years at least), others have advanced far beyond this stage,
and, in their planetary old age, are hastening towards their end--the
same end that inevitably awaits our own globe. The radiation of heat
into space gradually lowers the temperature until all the water is
turned into ice; that is the end of all organic life. The substance
of the rotating mass contracts more and more; the rapidity of its
motion gradually falls off. The orbits of the planets and of their
moons grow narrower. At length the moons fall upon the planets, and
the planets are drawn into the sun that gave them birth. The collision
again produces an enormous quantity of heat. The pulverized mass of the
colliding bodies is distributed freely through infinite space, and the
eternal drama of sun-birth begins afresh.

The sublime picture which modern astrophysics thus unveils before the
mind's eye shows us an eternal birth and death of countless heavenly
bodies, a periodic change from one to the other of the different
cosmogenetic conditions, which we observe side by side in the universe.
While the embryo of a new world is being formed from a nebula in
one corner of the vast stage of the universe, another has already
condensed into a rotating sphere of liquid fire in some far distant
spot; a third has already cast off rings at its equator, which round
themselves into planets; a fourth has become a vast sun whose planets
have formed a secondary retinue of moons, and so on. And between them
are floating about in space myriads of smaller bodies, meteorites,
or shooting-stars, which cross and recross the paths of the planets
apparently like lawless vagabonds, and of which a great number fall
onto the planets every day. Thus there is a continuous but slow change
in the velocities and the orbits of the revolving spheres. The frozen
moons fall onto the planets, the planets onto their suns. Two distant
suns, perhaps already stark and cold, rush together with inconceivable
force and melt away into nebulous clouds. And such prodigious heat
is generated by the collision that the nebula is once more raised to
incandescence, and the old drama begins again. Yet in this "perpetual
motion" the infinite substance of the universe, the sum total of its
matter and energy, remains eternally unchanged, and we have an eternal
repetition in infinite time of the periodic dance of the worlds, the
metamorphosis of the cosmos that ever returns to its starting-point.
Over all rules the law of substance.


The earth and its origin were much later than the heavens in becoming
the object of scientific investigation. The numerous ancient and modern
cosmogonies do, indeed, profess to give us as good an insight into the
origin of the earth as into that of the heavens; but the mythological
raiment, in which all alike are clothed, betrays their origin in
poetic fancy. Among the countless legends of creation which we find in
the history of religions and of thought there is one that soon took
precedence of all the rest--the Mosaic story of creation as told in
the first book of the Hexateuch. It did not exist in its present form
until long after the death of Moses (probably not until eight hundred
years afterwards); but its sources are much older, and are to be found
for the most part in Assyrian, Babylonian, and Hindoo legends. This
Hebrew legend of creation obtained its great influence through its
adoption into the Christian faith and its consecration as the "Word of
God." Greek philosophers had already, five hundred years before Christ,
explained the natural origin of the earth in the same way as that of
other cosmic bodies. Xenophanes of Colophon had even recognized the
true character of the fossils which were afterwards to prove of such
moment; the great painter, Leonardo da Vinci, of the fifteenth century,
also explained the fossils as the petrified remains of animals which
had lived in earlier periods of the earth's history. But the authority
of the Bible, especially the myth of the deluge, prevented any further
progress in this direction, and insured the triumph of the Mosaic
legend until about the middle of the last century. It survives even at
the present day among orthodox theologians. However, in the second half
of the eighteenth century, scientific inquiry into the structure of the
crust of the earth set to work independently of the Mosaic story, and
it soon led to certain conclusions as to the origin of the earth. The
founder of geology, Werner of Freiberg, thought that all the rocks were
formed in water, while Voigt and Hutton (1788) rightly contended that
only the stratified, fossil-bearing rocks had had an aquatic origin,
and that the Vulcanic or Plutonic mountain ranges had been formed by
the cooling down of molten matter.

The heated conflict of these "Neptunian" and "Plutonic" schools was
still going on during the first three decades of the present century;
it was only settled when Karl Hoff (1822) established the principle of
"actualism," and Sir Charles Lyell applied it with signal success to
the entire natural evolution of the earth. The _Principles of Geology_
of Lyell (1830) secured the full recognition of the supremely important
theory of continuity in the formation of the earth's crust, as opposed
to the catastrophic theory of Cuvier.[34] Palæontology, which had
been founded by Cuvier's work on fossil bones (1812), was of the
greatest service to geology; by the middle of the present century it
had advanced so far that the chief periods in the history of the earth
and its inhabitants could be established. The comparatively thin crust
of the earth was now recognized with certainty to be the hard surface
formed by the cooling of an incandescent fluid planet, which still
continues its slow, unbroken course of refrigeration and condensation.
The crumpling of the stiffened crust, "the reaction of the molten fiery
contents on the cool surface," and especially the unceasing geological
action of water, are the natural causes which are daily at work in the
secular formation of the crust of the earth and its mountains.

To the brilliant progress of modern geology we owe three extremely
important results of general import. In the first place, it has
excluded from the story of the earth all questions of miracle, all
questions of supernatural agencies, in the building of the mountains
and the shaping of the continents. In the second place, our idea of
the length of the vast period of time which had been absorbed in their
formation has been considerably enlarged. We now know that the huge
mountains of the palæozoic, mesozoic, and cenozoic formations have
taken, not thousands, but millions of years in their growth. In the
third place, we now know that all the countless fossils that are found
in those formations are not "sports of nature," as was believed one
hundred and fifty years ago, but the petrified remains of organisms
that lived in earlier periods of the earth's history, and arose by
gradual transformation from a long series of ancestors.


The many important discoveries which these fundamental sciences have
made during the nineteenth century are so well known, and their
practical application in every branch of modern life is so obvious,
that we need not discuss them in detail here. In particular, the
application of steam and electricity has given to our nineteenth
century its characteristic "machinist-stamp." But the colossal
progress of inorganic and organic chemistry is not less important. All
branches of modern civilization--medicine and technology, industry
and agriculture, mining and forestry, land and water transport--have
been so much improved in the course of the century, especially in the
second half, that our ancestors of the eighteenth century would find
themselves in a new world, could they return. But more valuable and
important still is the great theoretical expansion of our knowledge
of nature, which we owe to the establishment of the law of substance.
Once Lavoisier (1789) had established the law of the persistence of
matter, and Dalton (1808) had founded his new atomic theory with its
assistance, a way was open to modern chemistry along which it has
advanced with a rapidity and success beyond all anticipation. The same
must be said of physics in respect of the law of the conservation of
energy. Its discovery by Robert Mayer (1842) and Hermann Helmholtz
(1847) inaugurated for this science also a new epoch of the most
fruitful development; for it put physics in a position to grasp the
universal unity of the forces of nature and the eternal play of natural
processes, in which one force may be converted into another at any


The great discoveries which astronomy and geology have made during the
nineteenth century, and which are of extreme importance to our whole
system, are, nevertheless, far surpassed by those of biology. Indeed,
we may say that the greater part of the many branches which this
comprehensive science of organic life has recently produced have seen
the light in the course of the present century. As we saw in the first
section, during the century all branches of anatomy and physiology,
botany and zoology, ontogeny and phylogeny, have been so marvellously
enriched by countless discoveries that the present condition of
biological science is immeasurably superior to its condition a hundred
years ago. That applies first of all _quantitatively_ to the colossal
growth of our positive information in all those provinces and their
several parts. But it applies with even greater force _qualitatively_
to the deepening of our comprehension of biological phenomena, and
our knowledge of their efficient causes. In this Charles Darwin
(1859) takes the palm of victory; by his theory of selection he has
solved the great problem of "organic creation," of the natural
origin of the countless forms of life by gradual transformation. It
is true that Lamarck had recognized fifty years earlier that the
mode of this transformation lay in the reciprocal action of heredity
and adaptation. However, Lamarck was hampered by his lack of the
principle of selection, and of that deeper insight into the true
nature of organization which was only rendered possible after the
founding of the theory of evolution and the cellular theory. When we
collated the results of these and other disciplines, and found the
key to their harmonious interpretation in the ancestral development
of living beings, we succeeded in establishing the monistic biology,
the principles of which I have endeavored to lay down securely in my
_General Morphology_.


In a certain sense, the true science of man, rational anthropology,
takes precedence of every other science. The saying of the ancient
sage, "Man, know thyself," and that other famous maxim, "Man is the
measure of all things," have been accepted and applied from all time.
And yet this science--taking it in its widest sense--has languished
longer than all other sciences in the fetters of tradition and
superstition. We saw in the first section how slowly and how late
the science of the human organism was developed. One of its chief
branches--embryology--was not firmly established until 1828 (by Baer),
and another, of equal importance--the cellular theory--until 1838 (by
Schwann). And it was even later still when the answer was given to the
"question of all questions," the great riddle of the origin of man.
Although Lamarck had pointed out the only path to a correct solution
of it in 1809, and had affirmed the descent of man from the ape, it
fell to Darwin to establish the affirmation securely fifty years
afterwards, and to Huxley to collect the most important proofs of it
in 1863, in his _Place of Man in Nature_. I have myself made the first
attempt, in my _Anthropogeny_ (1874), to present in their historical
connection the entire series of ancestors through which our race has
been slowly evolved from the animal kingdom in the course of many
millions of years.


The number of world-riddles has been continually diminishing in the
course of the nineteenth century through the aforesaid progress of a
true knowledge of nature. Only one comprehensive riddle of the universe
now remains--the problem of substance. What is the real character of
this mighty world-wonder that the realistic scientist calls Nature or
the Universe, the idealist philosopher calls Substance or the Cosmos,
the pious believer calls Creator or God? Can we affirm to-day that the
marvellous progress of modern cosmology has solved this "problem of
substance," or at least that it has brought us nearer to the solution?

The answer to this final question naturally varies considerably
according to the stand-point of the philosophic inquirer and his
empirical acquaintance with the real world. We grant at once that the
innermost character of nature is just as little understood by us as it
was by Anaximander and Empedocles twenty-four hundred years ago, by
Spinoza and Newton two hundred years ago, and by Kant and Goethe one
hundred years ago. We must even grant that this essence of substance
becomes more mysterious and enigmatic the deeper we penetrate into the
knowledge of its attributes, matter and energy, and the more thoroughly
we study its countless phenomenal forms and their evolution. We do not
know the "thing in itself" that lies behind these knowable phenomena.
But why trouble about this enigmatic "thing in itself" when we have
no means of investigating it, when we do not even clearly know whether
it exists or not? Let us, then, leave the fruitless brooding over this
ideal phantom to the "pure metaphysician," and let us instead, as "real
physicists," rejoice in the immense progress which has been actually
made by our monistic philosophy of nature.

Towering above all the achievements and discoveries of the century
we have the great, comprehensive "law of substance," the fundamental
law of the constancy of matter and force. The fact that substance is
everywhere subject to eternal movement and transformation gives it the
character also of the universal law of evolution. As this supreme law
has been firmly established, and all others are subordinate to it, we
arrive at a conviction of the universal unity of nature and the eternal
validity of its laws. From the gloomy _problem_ of substance we have
evolved the clear _law_ of substance. The monism of the cosmos which we
establish thereon proclaims the absolute dominion of "the great eternal
iron laws" throughout the universe. It thus shatters, at the same time,
the three central dogmas of the dualistic philosophy--the personality
of God, the immortality of the soul, and the freedom of the will.

Many of us certainly view with sharp regret, or even with a profound
sorrow, the death of the gods that were so much to our parents and
ancestors. We must console ourselves in the words of the poet:

    "The times are changed, old systems fall,
    And new life o'er their ruins dawns."

The older view of idealistic dualism is breaking up with all its mystic
and anthropistic dogmas; but upon the vast field of ruins rises,
majestic and brilliant, the new sun of our realistic monism, which
reveals to us the wonderful temple of nature in all its beauty. In the
sincere cult of "the true, the good, and the beautiful," which is the
heart of our new monistic religion, we find ample compensation for the
anthropistic ideals of "God, freedom, and immortality" which we have

Throughout this discussion of the riddles of the universe I have
clearly defined my consistent monistic position and its opposition
to the still prevalent dualistic theory. In this I am supported by
the agreement of nearly all modern scientists who have the courage to
accept a rounded philosophical system. I must not, however, take leave
of my readers without pointing out in a conciliatory way that this
strenuous opposition may be toned down to a certain degree on clear
and logical reflection--may, indeed, even be converted into a friendly
harmony. In a thoroughly logical mind, applying the highest principles
with equal force in the entire field of the cosmos--in both organic and
inorganic nature--the antithetical positions of theism and pantheism,
vitalism and mechanism, approach until they touch each other.
Unfortunately, consecutive thought is a rare phenomenon in nature. The
great majority of philosophers are content to grasp with the right hand
the pure knowledge that is built on experience, but they will not part
with the mystic faith based on revelation, to which they cling with the
left. The best type of this contradictory dualism is the conflict of
pure and practical reason in the critical philosophy of the most famous
of modern thinkers, Immanuel Kant.

On the other hand, the number is always small of the thinkers who
will boldly reject dualism and embrace pure monism. That is equally
true of consistent idealists and theists, and of logical realists and
pantheists. However, the reconciliation of these apparent antitheses,
and, consequently, the advance towards the solution of the fundamental
riddle of the universe, is brought nearer to us every year in the
ever-increasing growth of our knowledge of nature. We may, therefore,
express a hope that the approaching twentieth century will complete
the task of resolving the antitheses, and, by the construction of a
system of pure monism, spread far and wide the long-desired unity
of world-conception. Germany's greatest thinker and poet, whose one
hundred and fiftieth anniversary will soon be upon us--Wolfgang
Goethe--gave this "philosophy of unity" a perfect poetic expression,
at the very beginning of the century, in his immortal poems, _Faust_,
_Prometheus_, and _God and the World_:

    "By eternal laws
    Of iron ruled,
    Must all fulfil
    The cycle of
    Their destiny."


[1] There are two English translations, _The Evolution of Man_ (1879)
and _The Pedigree of Man_ (1880).

[2] The English translation, by Dr. Hans Gadow, bears the title of _The
Last Link_.

[3] English translation, by J. Gilchrist, with the title of _Monism_.

[4] E. Haeckel, _Systematische Phylogenie_, 1895, vol. iii., pp.
646-50. (Anthropolatry means "A divine worship of human nature.")

[5] Cf. my Cambridge lecture, _The Last Link_, "Geological Time and

[6] As to induction and deduction, _vide_ _The Natural History of

[7] Rudolph Virchow, _Die Gründung der Berliner Universität und der
Uebergang aus dem Philosophischen in das naturwissenschaftliche
Zeitalter_. (Berlin; 1893.)

[8] Cf. chap. iv. of my _General Morphology_, 1866; _Kritik der
naturwissenschaftlichen Methoden_.

[9] _Systematische Phylogenie_, 1896, part iii., pp. 490, 494, and 496.

[10] Translated in the International Science Series, 1872.

[11] _Zell-Seelen und Seelen-Zellen._ Ernst Haeckel, _Gesammelte
populäre Vorträge. I. Heft._ 1878.

[12] Cf. E. Haeckel, _The Systems of Darwin, Goethe, and Lamarck_.
Lecture given at Eisenach in 1882.

[13] _Vide_ the translation of Dr. Hans Gadow: _The Last Link_. (A. &
C. Black.)

[14] Cf. Max Verworn, _Psychophysiologische Protisten-Studien_, pp.
135, 140.

[15] E. Haeckel, "General Natural History of the Radiolaria"; 1887.

[16] _Vide Natural History of Creation_, E. Haeckel.

[17] Law of individual variation. _Vide_ _Natural History of Creation_.

[18] Cf. E. Haeckel, _Systematic Phylogeny_, vol. i.

[19] Cf. _Anthropogeny_ and _Natural History of Creation_.

[20] Cf. _Natural History of Creation_.

[21] See chaps. xvi. and xvii. of my _Anthropogeny_.

[22] E. Haeckel, _A Visit to Ceylon_.

[23] Cf. _Monism_, by Ernst Haeckel.

[24] Cf. _Monism_, by Ernst Haeckel.

[25] Cf. _Monism_, by Ernst Haeckel.

[26] Reinke, _Die Welt als That_ (1899).

[27] Cf. _Monism_, by Ernst Haeckel.

[28] _The Last Link_, translated by Dr. Gadow.

[29] _General Morphology_, book 2, chap. v.

[30] Cf. _General Morphology_, vol. ii., and _The Natural History of

[31] _Vide_ _A Visit to Ceylon_, E. Haeckel, translated by C. Bell.

[32] _Collected Popular Lectures_; Bonn, 1878.

[33] As to the Greek paternity of Christ, _vide_ p. 328.

[34] Cf. _The Natural History of Creation_, chaps. iii., vi., xv., and


 Abiogenesis, 257, 369.

 Abortive organs, 264.

 Accidents, 216.

 Acrania, 166.

 Action at a distance, 217.

 Actualism, 249.

 Æsthesis, 225.

 Affinity, 224.

 Altruism, 350.

 Amphibia, 167.

 Amphimixis, 141.

 Ampitheism, 278.

 Ananke, 272.

 Anatomy, 22, etc.
   comparative, 24.

 Anaximander, 289, 379.

 Anthropism, 11.

 Anthropistic illusion, 14, etc.
   world-theory, 13.

 Anthropocentric dogma, 11, etc.

 Anthropogeny, 83.

 Anthropolatric dogma, 12.

 Anthropomorpha, 36.

 Anthropomorphic dogma, 12.

 Apes, 36, 37, 167.
   anthropoid, 37.

 Archæus, 43.

 Archigony, 257.

 Aristotle, 23, 268.

 Association, centres of, 183.
   of ideas, 121.
   of presentations, 121, 122.

 Astronomy, progress of, 366.

 Astro-physics, 368.

 Atavism, 142.

 Athanatism, 189.

 Athanatistic illusions, 205.

 Atheism, 290.

 Atheistic science, 260.

 Atom, the, 222.

 Atomism, 223.

 Atomistic consciousness, 187.

 Attributes of ether, 227.
   of substance, 216.

 Augustine of Hippo, 130.

 Auricular confession, 319, 359.

 Autogony, 257.

 Baer (Carl Ernst), 57.

 Bastian (Adolf), 103.

 Beginning of the world, 240, 247.

 Bible, the, 282, 362.

 Biogenesis, 257.

 Biogenetic law, 81, 143.

 Bismarck, 334.

 Blastoderm, 150, 155.

 Blastosphere, 153.

 Blastula, 153.

 Bruno (Giordano), 290, 317.

 Büchner (Ludwig), 93.

 Buddhism, 326, 355.

 Calvin, 130.

 Canonical gospels, 312.

 Carbon as creator, 256.
   theory, 257.

 Catarrhinæ, 35.

 Catastrophic theory, 74.

 Categorical imperative, 350.

 Causes, efficient, 258.
   final, 258.

 Celibacy, 358.

 Cell-love, 137.
   community, soul of the, 155.
   soul, 151.
   state, 157.

 Cellular pathology, 50.
   physiology, 48.
   psychology, 153, 177.
   theory, 26.

 Cenobitic soul, 155.

 Cenogenesis, 82.
   of the psyche, 144.

 Chance, 274.

 Chemicotropism, 64, 136.

 Chordula, 64.

 Chorion, 68.

 Christ, father of, 327.

 Christian art, 339.
   civilization, 356.
   contempt of the body, 354.
     animals, 355.
     nature, 355.
     self, 353.
     the family, 357.
     woman, 358.
   ethics, 352.

 Christianity, 347.

 Church and school, 362.
   state, 361.

 Cnidaria, 161.

 Conception, 64.

 Concubinage of the clergy, 358.

 Confession of faith, 302.

 Consciousness, 170.
   animal, 176.
   atomistic, 178.
   biological, 176.
   cellular, 177.
   development of, 185.
   dualistic, 182.
   human, 173.
   monistic, 182.
   neurological, 174.
   ontogeny of, 186.
   pathology of, 182.
   physiological, 180.
   transcendental, 180.

 Constancy of energy, 212, 231.
   matter, 212.

 Constantine the Great, 316.

 Constellations of substance, 218.

 Conventional lies, 323.

 Copernicus, 24, 320, 367.

 Cosmic immortality, 191.

 Cosmogonies, 234.

 Cosmological dualism, 257.
   creationism, 235.
   law, 211.
   perspective, 14.

 Cosmos, the, 229.

 Creation, 73, 79, 234.
   cosmological, 235.
   dualistic, 236.
   heptameral, 237.
   individual, 237.
   myths of, 236.
   periodic, 237.
   trialistic, 237.

 Cultur-kampf, 334.

 Cuvier, 74.

 Cyclostomata, 167.

 Cynopitheci, 46.

 Cytology, 26, etc.

 Cytopsyche, 151.

 Cytula, 64.

 Darwin (Charles), 78, etc.

 Decidua, 69.

 Deduction, 16.

 Demonism, 276.

 Descartes, 99, 355.

 Descent of the ape, 85, etc.
   of man, 87.
   theory of, 77.

 Design, 264, 266.
   in nature, 260.
   in organisms, 266.
   in selection, 261.

 Destruction of heavenly bodies, 243.

 Determinists, 130.

 Diaphragm, 31.

 Division of labor in matter, 229.

 Draper, 309, 333.

 Dualism, 20, etc.

 Du Bois-Reymond, 15 180, 235.

 Du Prel (Carl), 305.

 Duty, feeling of, 350.

 Dynamodes, 216.

 Dysteleology, 260.

 Echinodermata, 62.

 Ectoderm, 160.
   sense-cells in the, 293.

 Egoism, 350.

 Elements, chemical, 222.
   system of the, 222.

 Embryo, human, 64.

 Embryology, 54.

 Embryonic psychogeny, 144.
   sleep, 146.

 Empedocles, 23, 224.

 Encyclica (of Pius IX.), 323.

 End of the world, 247.

 Energy, kinetic, 231.
   potential, 231.
   principle of, 230.
   specific, 294.

 Entelecheia, 268.

 Entoderm, 160.

 Entropy of the universe, 247.

 Epigenesis, 56, 133.

 Ergonomy of matter, 229.

 Eternity of the world, 242.

 Ether, 225.

 Etheric souls, 199.

 Ethics, fundamental law of, 350.

 Evolution, theory of, 54, 239, 243.
   chief element in, 267.

 Experience, 16.

 Extra-mundane God, 288.

 Faith, confession of, 303.
   of our fathers, 304.

 Family, the, and Christianity, 357.

 Fate, 272.

 Fechner, 97, etc.

 Fecundation, 63.

 Fetishism, 276.

 Feuerbach (Ludwig), 295.

 Flechsig, 183.

 Foetal membranes, 66.

 Folk-psychology, 103.

 Forces, conversion of, 231.

 Frederick the Great, 194, 315.

 Galen, 23, 40.

 Gaseous souls, 199.
   vertebrates, 288.

 Gastræa, 160.
   theory of the, 60.

 Gastræads, 159.

 Gastrula, 61.

 Gegenbaur, 25, 30.

 Generation, theory of, 55.

 Genus, 73.

 Geology, periods of, 270.
   progress of, 373.

 Germinal disk, 57.

 Gills, 65.

 God, 275.
   the father, 277.
   the son, 277, 328.

 Goethe, 20, etc.

 Goethe's monism, 331.

 Golden Rule, the, 351.

 Gospels, 312.

 Gravitation, theory of, 217.

 Gut-layer, 159.

 Haller, 42.

 Harvey, 42.

 Helmholtz (Hermann), 213, 230.

 Heredity, psychic, 138.

 Hertz (Heinrich), 225.

 Hippocrates, 23.

 Histology, 26.

 Histopsyche, 156.

 Hoff (Carl), 250.

 Holbach (Paul), 193.

 Holy Ghost, 277, 326.

 Humboldt (Alexander), 343.

 Hydra, 161.

 Hylozoism, 289.

 Hypothesis, 299.

 Iatrochemicists, 45.

 Iatromechanicists, 45.

 Ideal of beauty, 338.
   of truth, 337.
   of virtue, 339.

 Ignorabimus, 180.

 Immaculate conception, 326.

 Immaterial substance, 221.

 Immortality of animals, 201.
   of the human soul, 188.
   of unicellular organisms, 190.
   personal, 192.

 Imperfection of nature, 264.

 Imponderable matter, 225.

 Impregnation, 64.

 Indeterminists, 130.

 Induction, 16.

 Indulgences, 359.

 Infallibility of the pope, 324.

 Instinct, 105, 123.

 Intellect, 125, etc.

 Intramundane God, 288.

 Introspective psychology, 95.

 Islam, 284.

 Janssen (Johannes), 316.

 Jehovah, 283.

 Journeys on foot, 364.

 Kant, 258, etc.

 Kant's metamorphosis, 92, etc.

 Kinetic energy, 231.
   theory of substance, 216.

 Kölliker, 26, 48.

 Lamarck, 76, etc.

 Lamettrie, 194.

 Landscape-painting, 343.

 Language, 126.
   study of, 363.

 Last judgment, 209.

 Lavoisier, 212.

 Leap of the gospels, miraculous, 312.

 Leydig, 27.

 Life, definition of, 39.

 Limits of our knowledge, 182.

 Love, 357.
   of animals, 355.
   of neighbor, 350.
   of self, 350.

 Lucretius Carus, 290.

 Lunarism, 281.

 Luther, 320.

 Lyell, 77, 250.

 Madonna, cult of the, 284, 327.

 Malphigi, 54.

 Mammals, 30, etc.

 Mammary glands, 31.

 Man, ancestors of, 82.

 Marsupials, 32, 86.

 Mass, 222.

 Materialism, 20.

 Mayer (Robert), 213, 377.

 Mechanical causality, 366.
   explanation, 259.
   theory of heat, 247.

 Mechanicism, 259.

 Mediterranean religions, the, 282.

 Memory, cellular, 12O.
   conscious, 121.
   histionic, 121.
   unconscious, 121.

 Mephistopheles, 279.

 Metabolism, 232.

 Metamorphoses of the cosmos, 372.
   of philosophers, 92.

 Metaphyta, 156.

 Metasitism, 153.

 Metazoa, 60, 157.

 Middle Ages, 315, 358.

 Mixotheism, 286.

 Mohammedanism, 284.

 Mohr (Friedrich), 213.

 Monera, 257, 369.

 Monism, 20, and _passim_.
   of energy, 254.
   of Spinoza, 331.
   of the cosmos, 255.

 Monistic anthropogeny, 252.
   art, 341.
   biogeny, 251.
   churches, 345.
   cosmology, 368.
   ethics, 347.
   geogeny, 248.

 Monotheism, 279.

 Monotrema, 32.

 Moon-worship, 281.

 Moral order of the universe, 269.

 Morula, 155.

 Mosaism, 283.

 Müller (Johannes), 25, 45, 262.

 Mythology of the soul, 135.

 Natural religion, 344.

 Navel-cord, 69.

 Neokantians, 349.

 Neovitalism, 264.

 Neptunian geology, 375.

 Neuro-muscular cells, 114.

 Neuroplasm, 91, 109.

 Neuropsyche, 162.

 Nomocracy, 9.

 Ontogenetic psychology, 103.

 Ontological creationism, 235.
   methods, 249.

 Orbits of the heavenly bodies, 241.

 Origin of movement, 15, 241.
   of feeling, 15, 241.

 Ovary, 63.

 Palingenesis, 82.
   of the psyche, 143.

 Pandera (the father of Christ), 328.

 Pantheism, 288.

 Papacy, 314.

 Papal ethics, 359.

 Papiomorpha, 37.

 Paul, 313, 357.
   epistles of, 312.

 Paulinism, 313.

 Pedicle of the allantois, 69.

 Perpetual motion, 245.

 Persistence of force, 212, 231.
   of matter, 212.

 Phroneta, 293.

 Phylogeny, 71, 81.
   of the apes, 51.
   systematic, 81.

 Physiology, 39.

 Phytopsyche, 157.

 Pithecanthropus, 87.

 Pithecoid theory, 82, etc.

 Pithecometra-thesis, 69, 85.

 Placenta, 32, 68.

 Placentals, 32, 86.

 Plasmodoma, 153.

 Plasmogony, 257.

 Plasmophaga, 154.

 Plato, 99, 197.

 Plato's theory of ideas, 269.

 Platodaria, 160.

 Platodes, 160.

 Platyrrhinæ, 35.

 Pneuma zoticon, 40.

 Polytheism, 276.

 Ponderable matter, 222.

 Preformation theory, 54.

 Primaria, 33.

 Primates, 33, 86.

 Primitive Christianity, 311.
   gut, 61, 161.

 Prodynamis, 216.

 Progaster, 161.

 Proplacentals, 85.

 Prosimiæ, 34.

 Prostoma, 161.

 Prothyl, 223.

 Protoplasm, 90.

 Protozoa, 60.

 Provertebræ, 166.

 Pseudo-Christianity, 321.

 Psychade theory, 178.

 Psyche, 88.

 Psychogeny, 135.
   phyletic, 149.
   post-embryonic, 146.

 Psychology, 88 et seqq.
   ontogenetic, 104.
   phylogenetic, 104.

 Psychomonism, 226.

 Psychophysics, 97.

 Psychoplasm, 91, 110.

 Pupa, sleep of the, 146.

 Pyknosis, 218.

 Pyknotic theory of substance, 218.

 Reason, 17, 125.

 Reflex action, 112.
   arches, 114.

 Reformation, the, 319.

 Religion a private concern, 361.

 Remak, 58.

 Revelation, 306.

 Reversion, 142.

 Romance of the Virgin Mary, 327.

 Romanes, 106.

 Rudimentary organs, 264.

 Saints, 284.

 Scale of emotion, 127.
   of memory, 120.
   of movement, 111.
   of presentation, 118.
   of reason, 122.
   of reflex action, 113.
   of will, 127.

 Scatulation theory, 55.

 Schleiden, 26, 47.

 School, and Church, 361.
   and State, 362.
   reform of the, 363.

 Schwann, 26, 47.

 Selachii, 166.

 Selection, theory of, 79.

 Self-consciousness, 171.

 Sense-knowledge, 297.
   organs, 293.

 Senses, philosophy of the, 295.

 Sentiment, 17, etc., 331.

 Siebold, 27.

 Simiæ, 34.

 Social duties, 351.
   instincts, 350.

 Solar systems, 241, 369.

 Solarism, 280.

 Soul, 88 _et seqq._
   apparatus of the, 162.
   blending of the, 141.
   creation of the, 135.
   division of the, 135.
   etheric, 199.
   gaseous, 199.
   histionic, 157.
   history of the, 167.
   hydra, 161.
   life of the, 90.
   liquid, 200.
   mammal, 167.
   nerve, 162.
   origin of the, 135.
   of the plant, 157.
   personal, 162.
   solid, 201.
   substance of the, 198.
   transmigration of the, 135.

 Sources of knowledge, 293.

 Space and time, 244.
   infinity of, 242.
   reality of, 244.

 Species, 73.

 Spectral analysis, 241.

 Spermarium, 63.

 Spermatozoa, 58.

 Spinal cord, 165.

 Spinoza, 21, 215, 290.

 Spirit world, 221.

 Spirit-rapping, 305.

 Spiritism, 304.

 Spiritualism, 20.

 Sponge, soul of the, 161.

 Stem-cell, 63, 138, 151.

 Stimulated movement, 113, 116.

 Stimuli, conduction of, 158.

 Strauss (David), 309, 313.

 Struggle for life, 270.

 Substance, 215.
   law of, 211, etc.
   structure of, 229.

 Superstition, 301.

 Süss (Edward), 250.

 Syllabus, 323.

 Synodikon (of Pappus), 312.

 Table-turning, 305.

 Teleological explanation, 259.

 Teleology, 258.

 Tetrapoda, 29.

 Thanatism, 189.
   primary, 192.
   secondary, 192.

 Theism, 276.

 Theocracy, 9.

 Theory, 299.

 Thought, organs of, 126, 183, 293.

 Time and space, 244.
   reality of, 246.

 Tissue, theory of, 26.

 Tissue-forming animals, 157.
   plants, 156.

 Transformism, 76.

 Trimurti, 278.

 Trinity, dogma of the, 277.
   monistic, 336.

 Triplotheism, 277.

 Tropesis, 225.

 Tropismata, 128.

 Tunicata, 165.

 Turbellaria, 161.

 Ultramontanism, 310.

 Understanding, 125.

 Unity of natural forces, 231.
   of substance, 214.

 Universum perpetuum mobile, 245.

 Uterus, 34.

 Vaticanism, 314.

 Vertebrates, 27, _passim_.

 Verworn (Max), 48, 116.

 Vesalius, 24.

 Vibration, theory of, 216.

 Virchow, 26, 50.

 Virchow's metamorphosis, 93.

 Vital force, 42, 262.

 Vitalism, 43, 262.

 Vivisection, 41.

 Vogt (Carl), 93.

 Vogt (J.E.), 218.

 Water-color drawing, 364.

 Weismann, 190.

 Will, liberty of the, 129.
   scale of the, 128.

 Wolff (C.F.), 56.

 Woman and Christianity, 358.

 World-consciousness, 171.

 World-riddles, number of, 15.

 Wundt (Wilhelm), 100, 171.

                                THE END

    Transcriber's notes:

    The following is a list of changes made to the original.
    The first line is the original line, the second the corrected one.

    (12) Consequently, the so-called history of the world"
    (12) Consequently, the so-called "history of the world"

    structure of the primates forces us to distingiush two
    structure of the primates forces us to distinguish two

    of the geneaology of our race; for man bears all the
    of the genealogy of our race; for man bears all the

    world of which we have direct and certain cognizanze
    world of which we have direct and certain cognizance

    the law of substance by Robert Mayer and Helmholz
    the law of substance by Robert Mayer and Helmholtz

    The more impotant of these works we owe to Romanes
    The more important of these works we owe to Romanes

    Formerly assistant and pupil of Helmholz, Wundt had early
    Formerly assistant and pupil of Helmholtz, Wundt had early

    all other viviporous animals, precisely because the complete
    all other viviparous animals, precisely because the complete

    recent students of the protists, afford conlcusive evidence
    recent students of the protists, afford conclusive evidence

    a thinker is very striking; in explaning it, it is not
    a thinker is very striking; in explaining it, it is not

    "have no individuals and no generations in the matazoic sense."
    "have no individuals and no generations in the metazoic sense."

    in his _Species and Studies_ in his eighty-fouth year
    in his _Species and Studies_ in his eighty-fourth year

    Chief Forms of Theism--Polytheism--Tritheism--Ampitheism
    Chief Forms of Theism--Polytheism--Triplotheism--Amphitheism

    faith, and that all these insiduous institutions are
    faith, and that all these insidious institutions are

    nor in the narnow prisons of our jail-like schools,
    nor in the narrow prisons of our jail-like schools,

    And it was done in many, and sometimes very romatic, ways.
    And it was done in many, and sometimes very romantic, ways.

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