THE NATURE OF THE SOUL
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
anthropology.
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
physiology.
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
observations.
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.