Chapter XVI: Part 16

A subtle and comprehensive thinker like Kant was naturally perfectly conscious of the existence of this inconsistency of his dualistic principles. He endeavored to meet it by his theory of antinomies, declaring that pure reason is bound to land in contradictions when it attempts to conceive the whole scheme of things as a connected totality. In every attempt to form a unified and complete view of things we encounter these unsolvable antinomies, or mutually contradictory theses, for both of which sound proof is available. Thus, for instance, physics and chemistry say that matter must consist of atoms as its simplest particles; but logic declares that matter is divisible _in infinitum_. On the one theory time and space are infinite; on the other theory, finite. Kant attempted to reconcile these contradictions by his transcendental idealism, by the assumption that objects and their connection exist only in our imagination, and not in themselves. In this way he came to frame the false theory of knowledge which is honored with the title of "criticism," while as a matter of fact it is only a new form of dogmatism. The antinomies are not explained by it, but thrust aside; nor was there more truth in the assertion that equal proof is available for theses and antitheses.

The famous work of Kant's earlier years, _The General Natural History and Theory of the Heavens_ (1755), was purely monistic in its chief features. It embodied a fine attempt "to explain the constitution and mechanical origin of the universe on Newtonian principles." It was mathematically established forty years afterwards by Laplace in his _Exposition du système du monde_ (1796). This fearless monistic thinker was a consistent atheist, and told Napoleon I. that there was no room for "God" in his _Mécanique celeste_ (1799). Kant, however, afterwards found that, though there was no rational evidence of the existence of God, we must admit it on moral grounds. He said the same of the immortality of the soul and the freedom of the will. He then constructed a special "intelligible world" to receive these three objects of faith; he declared that the moral sense compelled us to believe in a supersensual world, although pure theoretical reason is quite unable to form any distinct idea of it. The categorical imperative was supposed to determine our moral sense and the distinction between good and evil. In the further progress of his ethical metaphysics Kant expressly urged that practical reason should take precedence of theoretical--in other words, that faith is superior to knowledge. In this way he enabled theology and irrational faith to find a place in his system and claim supremacy over all rational knowledge of nature.

The older Greek philosophy had been purely monistic, Anaximander and his disciple Anaximenes (in the sixth century B.C.) conceiving the world in the sense of our modern hylozoism, but Plato introduced (two hundred years afterwards) the dualistic view of things. The world of bodies is real, accessible to our sensible experience, changeable and transitory; opposed to it is the world of spirits, only to be reached by thought, supersensual, ideal, immutable, and eternal. Material things, the objects of physics, are only transient symbols of the eternal ideas, which are the subject of metaphysics. Man, the most perfect of all things, belongs to both worlds; his material frame is mortal, the prison of the immortal and invisible soul. The eternal ideas are only embodied for a time in the world of bodies here below; they dwell eternally in the world of spirits beyond, where the supreme idea (God, or the idea of the good) controls all in perfect unity. The human soul, endowed with free-will, is bound to develop the three cardinal virtues (wisdom, fortitude, and prudence) by the cultivation of its three chief moral faculties (thought, courage, and zeal). These fundamental principles of Plato's teaching, systematically presented by his pupil Aristotle, met with a very general acceptance, as they could easily be combined with the teaching of Christianity which arose four hundred years afterwards. The great majority of later philosophic and religious systems followed the same dualistic paths. Even Kant's metaphysics is only a new form of it; only its dogmatic character is hidden by the ascription to it of the convenient title of the "critical" system.

Modern science has opened out to us immense departments of the real world that are accessible to observation and rational inquiry; but it has not taught us a single fact that points to the existence of an immaterial world. On the contrary, it has shown more and more clearly that the supposed world beyond is a pure fiction, and only merits to be treated as a subject for poetry. Physics and chemistry in particular have proved that all phenomena that come under our observation depend on physical and chemical laws, and that all can be traced to the comprehensive and unified law of substance. Anthropogeny has taught us the evolution of man from animal ancestors. Comparative anatomy and physiology have shown that his mind is a function of the brain, and his will not free; and that his soul, absolutely bound up with its material organ, passes away at death like the souls of other mammals. Finally, modern cosmology and cosmogony have found no trace whatever of the existence and activity of a personal and extramundane God. All that comes within the range of our knowledge is a part of the material world.

In his observations on the supersensual world Kant lays stress on the fact that it lies beyond the range of experience, and is known only by faith. Conscience, he thinks, assures us of its existence, but does not give us any idea of its nature; and so the three central mysteries of metaphysics are mere words without meaning. But, as nothing can be done with mere words, Kant's followers have attempted to put a positive substance into them, generally in relation to traditional ideas and religious dogmas. Not only orthodox Kantians, but even critical philosophers like Schleiden, have dogmatically asserted that Kant and his disciples have established the transcendental ideas of God, freedom, and immortality, just as Kepler, Newton, and Laplace established the laws of celestial motion. Schleiden imagined that this dogmatic affirmation would refute "the materialism of modern German science." Lange has shown, on the contrary, that such dogmatism is utterly foreign to the spirit of the _Critique of Pure Reason_, and that Kant held the three ideas to be quite incapable of either positive or negative proof, and so thrust them into the domain of practical philosophy. Lange says: "Kant would not see, as Plato would not see before him, that the intelligible world is a world of poetry, and has no value except in this respect." But if these ideas are mere figments of the poetic imagination, if we can form neither positive nor negative idea of them, we may well ask: What has this imaginary spirit-world to do with the pursuit of truth?

As I have raised the question of the limits of truth and fiction, I may take the opportunity of pointing out the general importance of this distinction. Undoubtedly man's knowledge is limited, from the very nature of our faculties or the organization of our brain and sense-organs. Hence, Kant is right when he says that we perceive only the phenomena of things, and not their inner essence, which he calls the "thing in itself." But he is wrong and altogether misleading when he goes on to doubt the reality of the external world, and says it exists only in our presentations--in other words, that life is a dream. It does not follow, from the fact that our senses and phronema can reach only a part of the properties of things, that we call into question their existence in time and space. But our rational craving for a knowledge of causes impels us to fill up the gaps in our empirical knowledge by our imagination, and thus form an approximate idea of the whole. This work of the imagination may be called "fiction" in a broad sense--hypotheses when they are in science, faith when they belong to religion. However, these imaginative constructions must always take a concrete form. As a fact, the imagination that constructs the ideal world is never content merely to assume its existence, but always proceeds to form an image of it. But these forms of faith have no theoretical value for philosophy if they contradict scientific truth, or profess to be more than provisional hypotheses; otherwise they may be of practical service, but are theoretically useless. Hence we fully recognize the great ethical and pedagogical value of poetry and myths, but are by no means disposed to give them precedence of empirical knowledge in our quest of the truth. I agree entirely with the excellent criticism of Kant which Albert Lange gives in his _History of Materialism_ (vol. ii.); but I am unable to follow him when he transfers his idealism from practical to theoretical questions, and urges the erroneous theory of knowledge derived from it in opposition to monism and realism. It is true that, as Lange says:

Kant did not lack the sense for the conception of this intelligible world (as an imaginative world); but his whole education and the period in which his mental life developed prevented him from indulging it. As he was denied the liberty of giving a noble form, free from all mediæval distortion, to the vast structure of his ideas, his positive philosophy was never fully developed. His system, with its Janus face, stands at the limit of two ages. He himself, in spite of all the defects of his deductions, is a teacher of the ideal. Schiller especially has grasped with prophetic insight the very essence of his teaching, and purified it of its scholastic dross. Kant held that we must only think, not see, the intelligible world; though what he thinks must have objective reality. Schiller has rightly brought the intelligible world visibly before us by treating it as a poet, and thus following in the footsteps of Plato, who, in contradiction to his own dialectic, reached his highest thought when he allowed the supersensual to become a thing of sense in the myth. Schiller, the poet of freedom, dared to carry freedom openly into the land of dreams and of shadows; then there arose under his hand the dreams and shadows of the ideal.

In view of the great influence that Schiller's idealism has had in the spread of Kant's practical moral philosophy, we may for a moment consider it in contrast with the realistic views of Goethe.

The profound opposition of the views of the two greatest poets of the classical period of German literature is rooted deep in their natures. This has been proved so often and so thoroughly, and has so frequently been represented as the complementary quality of the two poets, that I need merely recall it here. As for Goethe, I have, in my _General Morphology_, shown his historical importance in connection with the theory of evolution and the system of monism. With all his versatile occupations, this great genius found time to devote to the morphological study of organisms, and to establish his comprehensive biological theories on this empirical basis. His discovery of the metamorphosis of plants and his vertebral theory of the skull justify us in classifying him as one of the chief forerunners of Darwin. When I dealt with this in the fourth chapter of the _History of Creation_, I pointed out how great an influence these morphological studies, together with his idea of evolution, had on the realism of his philosophy. They led him direct to monism and to an admiration of Spinoza's monistic pantheism. Schiller had neither great interest nor clear insight for these studies. His idealistic philosophy disposed him rather to Kant's dualistic metaphysics and to an acceptance of the three central mysteries--God, soul, and freedom. Both Schiller and Goethe had a thorough knowledge of anthropology and psychology. But the anatomic and physiological studies that Schiller made as a military surgeon had very little influence on his transcendental idealism, in which the ethical-æsthetic element preponderated. On the other hand, Goethe's empirical realism was profoundly influenced by his medical studies at Strasburg, and especially by his later comparative anatomical and botanical investigations at Jena and Weimar.

The philosophic antithesis which we thus find in the biological foundations of the views of Goethe and Schiller represents to an extent the Janus face that the philosophic genius of the German people bears to our own day. Goethe, the realist, penetrated deep into the empirical study of the material world, and sought, with Spinoza, to establish the unity of the universe. Schiller, the idealist, lives rather in the spirit-world, and seeks, with Kant, to utilize its ethical ideals--God, freedom, and immortality--for the education of the human race. Both tendencies of thought have led the genius of Germany--like the genius of Greece, two thousand years ago--to a great number of vast intellectual achievements. Goethe wrought the ideal in his practical life, Kant discovered it, Schiller proclaimed it to be the fittest aim of the future.

It is wrong to conclude from isolated quotations from Goethe that he occasionally betrayed the dualism of Schiller in his opinions. Some of the remarks in this connection that Eckermann has left us from his conversations with Goethe must be taken very carefully. Generally speaking, this source is not reliable; many of the observations that the mediocre Eckermann puts into the mouth of the great Goethe are quite inconsistent with his character, and are more or less perverted. Hence, when recent high-placed orators declare at Berlin that Goethe saved the high ideals of God, freedom, and immortality, like Schiller, and thus borrow a certain support for their Christian belief, they only show how little they have grasped the profound antithesis of the views of the two poets. Goethe notoriously described himself as a "renegade non-Christian." The creed of the "great heathen" Goethe, as we find it in _Faust_ and _Prometheus_ and _God and the World_, and a hundred other magnificent poems, is pure monism, of the pantheistic character which we take to be alone correct--hylozoism; he is equally far from the one-sided materialism of Holbach or Carl Vogt and the extreme dynamism of Leibnitz and Ostwald. Schiller by no means shared this realistic view of things; his idealistic sense fled beyond nature into the spirit world. However, our theoretic hylozoism does not exclude practical idealism, as Goethe's whole life showed. On the other hand, princes and priests often let us see how easily theoretical idealism goes with practical materialism, or hedonism.

In the month of February, 1904, the centenary of the death of Kant was celebrated throughout the world of culture. In numbers of academic speeches and writings he was greeted as the greatest thinker of Germany. He died on the same date (February 12th) on which Darwin was born five years later. It is unquestionable that Kant has had an immense influence on the whole development of German philosophy. But while recognizing his extraordinary genius, we must not be blind to the glaring contradictions and defects of his dualist system. From the monistic point of view, we can only regard his profound influence during the whole of the nineteenth century as mischievous. Most certainly he had a quite exceptional talent for philosophic speculation and penetrating thought, and he added to his great mental qualities a blameless character and an undeniable sense of truth in life (though not in thought). It was a serious misfortune for Kant and for the philosophic school he led that his education prevented him from acquiring a thorough knowledge and correct conception of the real world. Shut up throughout life within the narrow bounds of his native town, Königsberg, he never travelled beyond the frontier of Prussia, and so did not obtain that knowledge of the world that comes of travelling. In the study of nature he confined himself to the physics of the inorganic world, in the study of man to the immortal soul. At the close of his university studies Kant had to earn his living as a house-teacher for nine years (from twenty-two to thirty-one), just at the most important period of his life, in which the independent development of the personal and scientific character is decided when the academic studies are over.

In such adverse circumstances of mental adaptation a deep mystic trait, which had been inherited from pious parents and confirmed by the strictly religious training of his early years, was fixed in Kant's character. Hence it was that faith in the three central mysteries came upon him more and more in later years: he gave them precedence over all the attainments of theoretical reason, while granting that we can form neither a negative nor positive idea of them. But how can the belief in God, freedom, and immortality determine one's whole view of life as a postulate of practical reason if we cannot form any definite idea of them?

Every philosophy that deserves the name must have clear ideas as the bases of its thought-structure; it must have definite views in connection with its fundamental conceptions. Hence most of Kant's followers have not been content to follow his direction merely to _believe_ in the three central mysteries; they have sought to associate definite mental pictures with the empty concepts of God, freedom, and immortality. In this they have drawn upon the religious imagination, and have passed from the real knowledge of nature into the transcendental realm of poetry. Monism, based on this real knowledge of nature, has to keep clear of such dualism.

The extraordinary glorification of Kant that took place on the occasion of his centenary must have seemed strange to many scientists who recognize in his idealism one of the greatest hinderances to the spread of the modern monistic philosophy of nature. But it is not difficult to explain this. We must remember, in the first place, the contradictory views that are embodied in Kant's system; every one could find in Kant's works something to correspond to his own convictions--the monistic physicist could read of the mechanical sway of natural law throughout the whole knowable world, and the dualistic metaphysician of the free play of the divine aim in the spiritual world. The physician and physiologist would note with satisfaction that in his criticism of pure reason Kant had been unable to find any evidence for the existence of God, the immortality of the soul, or the freedom of the will. The jurist and theologian would find with equal gratification that in the practical reason Kant claims these three central dogmas as necessary postulates. I have shown to some extent, in the sixth chapter of the _Riddle_, how these irreconcilable contradictions in Kant's system are due to a psychological metamorphosis.

It is just these very contradictions, which run through Kant's philosophy from beginning to end, that maintain its popularity. Educated people who desire to form a view of life rarely read Kant's difficult (and often obscure) works in the original, but are content to learn from extracts, or from a history of philosophy, that the Königsberg thinker succeeded in squaring the circle, or in reconciling natural science with the three central dogmas of metaphysics. The "higher powers," who are particularly concerned to save the latter, favor the teaching of Kant's dogmas, because it closes the way to real explanation and prevents independent thinking. This is especially true of the ministers of public instruction in the two chief German states--Prussia and Bavaria. In their open attempt to subordinate the school to the Church, they desire, above all, the primacy of practical reason--that is to say, the subjection of pure reason to faith and revelation. In German universities to-day belief in Kant is a sort of ticket of admission to the study of philosophy. The reader who would realize the pernicious effect of this official faith in Kant on the advance of scientific knowledge will do well to read the able criticism in the brilliant posthumous work of Paul Rée.

In the face of the dualism which still prevails in the academic teaching of philosophy (especially in Germany) we must base our monistic system on the universality of the law of substance. This harmoniously combines the laws of the conservation of matter and of energy. As I have fully explained my own conception of this law in the twelfth chapter of the _Riddle_, I will only say here that its validity is quite independent of any particular theory of the relations of matter and force.[12] The materialism of Holbach and Büchner lays a one-sided stress on the importance of matter: the dynamism of Leibnitz and Ostwald on that of force. If we avoid these extremes, and conceive matter and force as inseparable attributes of substance, we have pure monism, as we find it in the systems of Spinoza and Goethe. We might then substitute for the word "substance" as Hermann Cröll does, the term "force-matter." The further question as to the correctness of any particular physical conception of matter is quite independent of this.

The two knowable attributes or inalienable properties of substance, without which it is unthinkable, were described by Spinoza as extension and thought; we speak of them as matter and force. The "extended" (or space-occupying) is matter; and in Spinoza "thought" does not mean a particular function of the human brain, but energy in the broadest sense. While hylozoistic monism conceives the human soul in this sense as a special form of energy, the current dualism or vitalism affirms, on the authority of Kant, that psychic and physical forces are essentially different; that the former belong to the immaterial and the latter to the material world. The theory of psycho-physical parallelism, as developed especially by Wundt (1892), gives a very sharp and definite expression to this dualism; it says that "physical processes correspond to every psychic phenomenon, but the two are completely independent of each other and have no natural causal connection."

This wide-spread dualism finds its chief support in the difficulty of directly connecting the processes of sensation with those of movement; and so the one is regarded as a psychic and the other as a physical form of energy. The conversion of the outer stimulus (waves of light, sound, etc.) into an inner sensation (sight or hearing) is regarded by monistic physiology as a conversion of force, a transformation of photic or acoustic energy into specific nerve-energy. The important theory of the specific energy of the sensory nerves, as formulated by Johannes Müller, forms a bridge between the two worlds. But the idea which these sensations evoke, the central process in the thought-organ or phronema that brings the impressions into consciousness, is generally regarded as an incomprehensible mystery. However, I have endeavored to prove, in the tenth chapter of the _Riddle_, that consciousness itself is only a special form of nervous energy, and Ostwald has lately developed the theory in his _Natural Philosophy_.

The processes of movement which we observe in every change of one form of energy into another, or every passage of potential into actual energy, are subordinate to the general laws of mechanics. The dualist metaphysic has rightly said that the mechanical philosophy does not discover the inner causes of these movements. It would seek these in psychic forces. On our monistic principles they are not immaterial forces, but based on the general sensation of substance, which we call _psychoma_, and add to energy and matter as a third attribute of substance.

The difficulty of combining our monism with Spinoza's doctrine of substance is met by detaching the idea of energy from sensation and restricting it to mechanics, so as to make movement a third fundamental property of substance with matter (the "extended") and sensation (the "thinking"). We may also divide energy into active (= will in the sense of Schopenhauer) and passive (= sensation in the broadest sense). As a matter of fact, the energy to which modern energism would reduce all phenomena has not an independent place in Spinoza's system besides sensation; the attribute of thought (the psyche, soul, force) comprises the two. I am convinced that sensation is, like movement, found in all matter, and this trinity of substance provides the safest basis for modern monism. I may formulate it in three propositions: (1) No matter without force and without sensation. (2) No force without matter and without sensation. (3) No sensation without matter and without force. These three fundamental attributes are found inseparably united throughout the whole universe, in every atom and every molecule. In view of the great importance of this view for our hylonistic system of monism, it may be well to consider each of these three attributes in connection with the law of substance.

_A._ MATTER.--As extended substance, matter occupies infinite space, and each individual body forms a part of the universe as real substance. The law of the conservation of matter teaches us that the sum of matter is eternal and unchangeable. This applies equally to the various kinds of matter which we call the chemical elements, or ponderable matter, and to the ether that fills the spaces between the atoms and molecules, or imponderable matter. The mischievous depreciation of matter (and the consequent disdain of materialism) and its antithesis to "spirit" is partly due to the use of such phrases as "raw" and "dead" matter, and partly to the deep-rooted mysticism we have inherited from barbaric ancestors, and find it hard to shake off.

_B._ ENERGY.--All parts of the substance that fills infinite space are in constant and eternal motion. Every chemical process and every physical phenomenon is accompanied by a change in the position of the particles which compose the matter. The law of the conservation of energy teaches us that the sum of force or energy that is ever at work in the universe is unchangeable. In the formation or decomposition of a chemical compound the particles of matter move about, and so in every mechanical, thermic, electric, and other process. The changes that take place depend on a constant change of force, both in organic and inorganic bodies; one form of force is converted into another without a particle of the whole being lost. This law of the conservation of force has lately been called, as a rule, the conservation of energy (or the principle of energy) since the ideas of force and energy have been more clearly distinguished in physics; energy is now usually defined as the product of force and direction. It must be noted, however, that the word "energy" (as an equivalent to "work" in the physical sense) is still used in many different senses, as is also the word "force." Others define energy as "work or all that comes of work and may be converted into work." One particular school of voluntarism (Wundt) reduces the motive-force of energy to will. Crusius said in 1744: "Will is the dominating force in the world." And Schopenhauer defines the world (or substance) as "will and presentation."

_C._ SENSATION.--In describing sensation (in the broadest sense) as a third attribute of substance, and separating "sensitive substance" from energy as "moving substance," I rely on the observations I made in the thirteenth chapter of the _Riddle_ on sensation in the organic and inorganic world. I cannot imagine the simplest chemical and physical process without attributing the movements of the material particles to unconscious sensation. In this sense the chemist speaks every day of a sensitive reaction, and the photographer of a sensitive plate. The idea of chemical affinity consists in the fact that the various chemical elements perceive the qualitative differences in other elements, experience "pleasure" or "revulsion" at contact with them, and execute their specific movements on this ground. The sensitiveness of the plasm to all kinds of stimuli, which is called "soul" in the higher animals, is only a superior degree of the general irritability of substance. Empedocles and the panpsychists spoke in the same sense of sensation and effort in all things. As Nägeli said: "If the molecules possess something that is related, however distantly, to sensation, it must be comfortable to be able to follow their attractions and repulsions; uncomfortable when they are forced to do otherwise. Thus we get a common spiritual bond in all material phenomena. The mind of man is only the highest development of the spiritual processes that animate the whole of nature." These views of the distinguished botanist fully agree with my monistic principles.

When sensation in the widest sense (as _psychoma_) is joined to matter and energy as a third attribute of substance, we must extend the universal law of the permanence of substance to all three aspects of it. From this we conclude that the quantity of sensation in the entire universe is also eternal and unchangeable, and that every change of sensation means only the conversion of one form of psychoma into other forms. If we start from our own immediate sensations and thoughts, and look out on the whole mental life of humanity, we see through all its continuous development the constancy of the psychoma, which has its roots in the sensations of each individual. This highest achievement of the work of the plasm in the human brain was, however, first developed in the sensations of the lower animals, and these are in turn connected by a long series of evolutionary stages with the simpler forms of sensation that we find in the inorganic elements, and that reveal themselves in chemical affinity. Albrecht Rau expressly says in his excellent _Sensation and Thought_ (1896) that "perception or sensation is a universal process in nature. This involves, moreover, the possibility of reducing thought itself to this universal process." Recently Ernst Mach has said, in his _Analysis of Sensation and the Relation of the Physical to the Psychical_, that "sensations are the common elements of all possible physical and psychic occurrences, and consist simply in the different mode of the combination of the elements and their dependence on each other." It is true that Mach, in his one-sided emphasis of the subjective element of sensation, goes on to form a similar psychomonism to that of Verworn, Avenarius, and other recent dynamists; but the fundamental character of his system is purely monistic, like the energism of Ostwald.

In thus uniting sensation with force and matter as an attribute of substance, we form a monistic trinity, and are in a position to do away with the antitheses that are rigidly maintained by dualists between the psychic and the physical, or the material and the immaterial world. Of the three great monistic systems materialism lays too narrow a stress on the attribute of matter, and would trace all the phenomena of the universe to the mechanics of the atoms or to the movements of their ultimate particles. Spiritualism, with equal narrowness, builds on the attribute of energy; it would either explain all phenomena by motor forces or forms of energy (energism), or reduce them to psychic functions, to sensation or psychic action (panpsychism). Our system of hylonism (or hylozoism) avoids the faults of both extremes, and affirms the identity of the psyche and the physis in the sense of Spinoza and Goethe. It meets the difficulties of the older theory of identity by dividing the attribute of thought (or energy) into two co-ordinate attributes, sensation (psychoma) and movement (mechanics).

XX

MONISM

Defence of monism--Pure and applied science (theoretic and practical reason)--Pure (theoretical) sciences: physics, chemistry, mathematics, astronomy, geology; biology, anthropology, psychology, philology, history--Applied (practical) sciences: medicine, psychiatry, hygiene, technology, pedagogics, ethics, sociology, politics, jurisprudence, theology--Antinomy of the sciences--Rational and dogmatic disciplines--Correlation of the sciences--Faculties--Reform of education--The ideal world--Harmony of monism.

Now that we have reached the end of our long journey, we may take a general survey of the path we have pursued, and say how far we owe our progress to the monistic philosophy. In doing so, we shall at once justify our own point of view and indicate the relation of biology to the other sciences. I feel the more bound to do this as the present volume is not only a necessary supplement to the _Riddle_, but at the same time my last philosophic work. At the end of my seventieth year I would supply some of the defects of the _Riddle_, answer some of the most stringent criticisms directed against it, and as far as possible complete the philosophy of life at which I worked for half a century.

In inviting my readers to accompany me once more through the broad domain of the monistic philosophy I must, as their modest guide, show scientific justification at the narrow entrance--produce, so to say, the ticket of admission to this investigation. The academic philosophy which still controls the German universities watches every door with jealous eyes, and has an especial concern to keep out modern biology. Official German philosophy is still for the most part taken up with a mediæval metaphysic and the dualism of Kant, the openly dogmatic character of which it greets as "criticism." In the course of the forty years during which I have taught as ordinary professor of zoology at Jena I have had occasion to assist at several hundred examinations of doctors, teachers, etc., in which distinguished representatives of philosophy were examiners. I saw that nearly always the chief stress was laid on a kind of conceptual gymnastics and self-observation, and on the correct knowledge of the innumerable errors which the (mainly dualistic) leaders of ancient and modern philosophy have left us in their vast literature. The central feature of the whole scheme is Kant's theory of knowledge, the defects and one-sidedness of which I have treated in the first and nineteenth chapters. In psychology a most extensive knowledge of psychic powers on the basis of the introspective method is demanded; the physiological analysis of the "soul" and the anatomic study of the phronema are carefully avoided, as are also the comparative and genetic study of the mind. Many of our metaphysicians go even farther and regard philosophy as a separate science--a sublime "mental science," quite independent of the common empirical sciences. One is tempted to quote the saying of Schopenhauer: "It is a sure sign of a philosopher that he is not a professor of philosophy." In my opinion, every educated and thoughtful man who strives to form a definite view of life is a philosopher. As queen of the sciences, philosophy has the great task of combining the general results of the other sciences, and of bringing their rays of light to a focus as in a concave mirror. The various tendencies of thought that arise in such numbers have all a right to scientific respect and discussion, the monistic minority no less than the dualistic majority. We have to inquire, then, how far monism has succeeded in gaining firm foothold in the various fields of science, and we may begin with a distinction between pure (theoretical) and applied (practical) science.

Pure philosophy aims at a knowledge of the truth by means of pure reason, as I explained in the first chapter. However, this theoretical philosophy finds itself in most of the sciences in direct and frequently important relations to practical life, and so in the form of applied philosophy becomes a weighty factor in civilization. In this the real claims of practical life are often in contradiction to the ideal tenets of the scientifically grounded theory. In such cases, in my opinion, the pure pursuit of the truth must take precedence of applied philosophy. I thus dissent entirely from the view of Kant, who expressly gives precedence to practical reason, and subordinates theoretical reason to it. Kant's error was fated to have a terrible influence, because the dominant authorities in Church and state eagerly embraced it to insure everywhere the supremacy of the dogmas of practical reason over the attainments of pure critical reason.

From the point of view of natural monism we may take physics in the wider sense as the fundamental science. The term _physis_ (the Greek equivalent of the Latin "nature"), in its original meaning, comprises the whole knowable world--Kant's _mundus sensibilis_. His supersensual or "intelligible" world is, on his own definition, the object of faith, not knowledge. It is very remarkable to find a thinker like Kant contradicting himself already in his fundamental distinction of the two worlds. How can the supersensual world, with its three central mysteries (God, freedom, and immortality), be described as intelligible (_i.e._, knowable) when it is proved by pure reason that the human mind is incapable of knowing it, or of forming any positive or negative idea of it? _Lucus a non lucendo!_ We may, therefore, leave this supernatural metaphysical world to faith and fiction, and confine our studies to the real physical world, nature. The idea of physics as a comprehensive natural philosophy, as it was conceived in classic Greece, has been more and more restricted in the course of time. To-day it is generally taken to mean the science of the phenomena of inorganic nature, their empirical determination by observation and experiment (experimental physics), and their reduction to fixed natural laws and mathematical formulæ (theoretical or mathematical physics). Of late a distinction has been drawn between the physics of mass and the physics of ether; the one deals with mechanics, the movement and equilibrium of ponderable matter, of solid, fluid, and gaseous bodies (statics and dynamics, gravitation, acoustics, meteorology); the other is occupied with the phenomena of ether (or imponderable matter) and its relations to mass (electricity, galvanism, magnetism, optics, and calorics). In all these branches of inorganic physics the monistic view is now generally received, and all attempt at dualistic explanation abandoned.

The vast department of chemistry, which has now become so important both for theoretical and practical purposes, is really only a part of physics. But while modern physics restricts itself to the study of inorganic forms of energy and their conversions, chemistry, as the science of matter, takes up the study of the qualitative differences between the various kinds of ponderable matter. It divides ponderable bodies into some seventy-eight elements, the relations of which to each other have been determined in the periodic system of the elements, and their probable common origin from some primitive matter (prothyl) been shown. The constant features of chemical combinations which have been established by the analysis and synthesis of the elements, and especially the law of simple and multiple proportions discovered in 1808, led to the empirical determination of the atomic weight of the elements and to the chemical theory of the atom. The acceptance of these atoms (as space-filling separate particles of matter--however we may regard them in other respects) is an indispensable hypothesis in chemistry, like the hypothesis of the molecule in physics. Modern dynamism (or energism) is wrong when it thinks it can dispense with these hypotheses and replace the atoms by the notion of immaterial non-spatial points of force. However, in both the dynamic and the material school monism is retained in every department of chemistry.

Modern science considers the ultimate aim of all research to be the exact determination of phenomena in measure and number, or the reduction of all general knowledge to mathematically formulated laws. As the great Laplace established his system mathematically, it has lately been claimed that a comprehensive (ideal) Laplace-mind could embrace the whole past, present, and future of the universe in a single gigantic mathematical formula. Kant has expressed this exaggerated estimate of mathematics in the phrase: "Every science is only true science in proportion as it is amenable to mathematical treatment"; and to this he has added the second error that the mathematical axioms (being necessary and universal truths) belong to the _a priori_ constitution of the mind, and are independent of experience (_a posteriori_). However, John Stuart Mill and others have shown that the fundamental ideas of mathematics are acquired originally, like those of any other science, by abstraction from experience; and the modern phylogeny of the mind has confirmed this empirical view. We must remember, moreover, that mathematics deals only with quantitative relations in time and space, and not with the qualitative features of bodies. In fact, Kant himself showed that mathematics only answers for the absolute _formal_ correctness of conclusions it draws from given premises, and has no influence on the premises themselves. Hence, when we examine the abstract thinking-power of the phronema in its mathematical operations physiologically and phylogenetically, we find that even this "exact fundamental science" is only accessible to pure monism and excludes all dualism. The great regard which mathematics enjoys as an exact science in all branches of knowledge is chiefly due to its _formal accuracy_, and to the possibility of expressing infallibly spatial and time quantities in number and mass.

Astronomy is one of the older sciences that took definite shape thousands of years ago, and received a solid mathematical foundation. Observations of the movements of the planets and eclipses of the sun were conducted by the Chinese, Chaldeans, and Egyptians several thousand years before Christ. Christ himself had no more suspicion of these great cosmological discoveries than of the systems which the Greek natural philosophers had built up three hundred to six hundred years before his birth. After Copernicus had destroyed the geocentric system in 1543, and Newton had provided a mathematical basis for the new heliocentric system by his theory of gravitation in 1686, cosmogony was firmly established in a monistic sense by the _General Natural History of the Heavens_ of Kant, and the _Mécanique Céleste_ of Laplace. Since that time there has been no question of the conscious action of a Creator in any part of astronomy. Astrophysics has enlarged our knowledge of the physical features, and astrochemistry (by means of spectrum analysis) of the chemical nature of the other heavenly bodies. The monism of the physical universe has now been established.

Geology was not developed into an independent science until towards the end of the eighteenth century, and did not extinguish the earlier notion of the creation of the earth until after 1830, when the principle of continuity and evolution was established. The oldest part of the science is mineralogy; the great practical value of the rocks, and especially the metals obtained from them, having appealed to man's interest thousands of years ago. In the Stone Age, Bronze Age, Iron Age, etc., the material for weapons and tools was provided by stone and metal. Afterwards the development of mining led to a closer acquaintance with these metals. But no notice was taken of the fossil remains of animals and plants until the close of the Middle Ages. It was not until the eighteenth century that students began to perceive the great significance of these "creation-medals," and at the beginning of the nineteenth paleontology arose as an independent science, and proved equally important to geology and biology. Other branches of geology, such as crystallography, have also made considerable progress during the last half-century, with the aid of physics and chemistry. All these sections of geology, especially geogeny, or the science of the natural development of the earth, are now recognized to be purely monistic sciences.

In the five branches of science I have enumerated, pure monism has been universally and exclusively admitted (as far as they relate to inorganic nature) in the second half of the nineteenth century. There is no question in them to-day of the wisdom and power of the Creator. This is equally true of geology, astronomy, mathematics, chemistry, and physics. It is otherwise with the remaining sciences which deal with organic nature; in these we have not yet succeeded in giving a physical explanation and mathematical formulation of all phenomena. Hence vitalism enters with its dualistic notions, and splits the science into two different branches--natural science (physics in the wider sense) and mental science (metaphysics); fixed natural laws are supposed to rule only in the former, while in the latter we still have the "freedom" of the spirit and the supernatural. This applies, first of all, to biology in the broadest sense (including anthropology and all the sciences that relate to man). In the preceding chapters of biological philosophy we have sought to refute vitalism in every form, and to secure the exclusive acceptance of monism and mechanicism in every branch of the science of life.

Anthropology is still, as it has been for centuries, taken in many different senses. In the widest sense, it embraces the whole vast science of man, just as zoology (in my opinion) deals with all parts of the animal world. Since I regard anthropology as a part of zoology, I naturally extend the principles of monism to both. However, this general monistic conception of the science of man has met with only a restricted acceptance up to the present. As a rule, the term "anthropology" is restricted to the natural history of man, which includes the anatomy and physiology of the human organism, embryology, prehistoric research, and a small part of psychology. But this "official anthropology," as most of our anthropological societies (especially in Germany) conceive it, generally excludes phylogeny, the greater part of psychology, and all the mental sciences, which are regarded as metaphysical in the narrower sense. I endeavored to show in my _Anthropogeny_ thirty years ago that man (as a placental mammal of the order of primates) is no less unified an organism (with body and soul) than any other vertebrate, and that, therefore, every aspect of his being should be dealt with monistically.

As is well known, the views of experts and laymen alike are very much divided as to the place of psychology in the scheme of the sciences. The great majority of the professional psychologists, and of educated people generally, adhere still to the antiquated dogma, with its religious foundation, that man's soul is immortal and an independent immaterial entity. This dualistic view has been supported in the schools especially by the authority of Plato, Descartes, and Kant; in religion by the authority of Christ, Paul, and Mohammed; in education and the state by the authority of most governments; and in physiology by most of the older, and even some recent, physiologists. On this view, psychology is a special mental science, having only an external and limited connection with natural science. But modern comparative and genetic psychology, the anatomy and physiology of the brain, have, in the course of the last forty years, established the monistic view that psychology is a special branch of cerebral physiology, and that therefore all its parts and their application belong to this section of biology. The soul of man is a physiological function of the phronema. As I have fully explained the monistic conception of psychology in chapters vi.-xi. of the _Riddle_, and supported it with all the arguments of anatomy, physiology, ontogeny, and phylogeny in my _Anthropogeny_, I need not go further into the subject.

The science of language shares the fate of its sister, psychology; by one section of its representatives it is taken monistically as a natural science, and by another section it is dualistically conceived as a branch of mental science. On the old metaphysical view, speech was regarded as an exclusive property of man, either a gift of the gods or an invention of social man. But in the course of the nineteenth century the monistic and physiological position that speech is a function of the organism, and has been gradually developed like all other functions, has been established. The comparative psychology of the higher animals showed that in various classes the thoughts, feelings, and desires of the gregarious animals are communicated partly by signs or touch, partly by sounds (the chirrup of the cricket, the cry of the frog, the whistle of many reptiles, song of birds and singing-apes, roaring of carnivora and ungulates, etc.). The ontogeny of speech showed that its gradual development in the child is (in accordance with the biogenetic law) a recapitulation of its phylogenetic process. Comparative philology taught that the languages of the different races have been formed polyphyletically, or independently of each other. The experimental physiology and pathology of the brain showed that a definite small region of the cortex (the Broca fissure) is the centre of speech, and that this central organ, in conjunction with other parts of the phronema and the larynx (the peripheral organ), produces articulate speech.

Historical science is, like philology or psychology, still conceived in different senses by experts. Very often history is wrongly taken to mean the record of events that have occurred in the course of the development of civilized life--the history of peoples and states (humorously described as "the history of the world"), of civilization, of morals, etc. This is merely an anthropocentric feeling that in the strictly scientific sense "history" can only be used for the record of man's doings. In this sense history is opposed to nature, the one dealing with the province of morally free phenomena (with preconceived aim), and the other comprising the province of natural law (without preconceived aim). As if there were no "natural history," or as if cosmogony, geology, ontogeny, and phytogeny were not historical sciences! Although this dualistic and anthropistic view still prevails in our universities, and state and Church protect the venerable tradition, there can be no doubt that sooner or later it will be replaced by a purely monistic philosophy of history. Modern anthropogeny shows us the intimate connection between the evolution of the human individual and that of the race; and by means of prehistoric and phylogenetic research it joins what is called the history of the world to the stem-history of the vertebrates.

Medicine belongs to the front rank of practical or applied sciences. In its long and interesting history it teaches how it is only a monistic knowledge of nature, not a dualistic notion of revelation, that affords the foundations of true science and the profitable application of this to the most important aspects of practical life. Medicine was originally the business of the priests, and for thousands of years it was under the influence of mystic and superstitious ideas which were connected with religious dogmas. However, two thousand years ago the great physicians of classic antiquity made a serious effort to provide a solid base for medical practice by a thorough anatomic and physiological study of the human frame. But in the general reaction of the Middle Ages superstitious and miraculous ideas once more defeated independent scientific investigation. Disease was supposed to be the work of evil spirits (as Christ thought) which had to be exorcised. Miracles are still thought to take place, even in cultured circles. I need only mention the wonders of patent medicines, magnetic cures, Christian Science, and other charlatanry. However, the great development of science in the nineteenth century, especially the astonishing advance of biology about the middle of the century, gradually shaped medicine into the monistic science which assuages so much pain and suffering in humanity to-day. Pathology, the science of disease, and therapeutics, the rational science of healing, are grounded now on the safe methods of physics and chemistry and a thorough knowledge of the human organism. Disease is no longer regarded as a special entity that comes on the body like an evil spirit or mysterious organism, but is conceived as a baneful disturbance of its normal activity. Pathology is only a branch of physiology; it studies the changes that take place in the tissues and cells under abnormal and dangerous conditions. When the causes of these changes are poisons or foreign organisms (such as bacteria or amœbæ), the art of healing has to remove them and restore the normal equilibrium of the functions.

The science of mental disease is a special branch of medicine; it has the same relation to it as psychology has to physiology. However, as pathological psychology it deserves special consideration, not only on account of its extreme practical importance, but also because of its theoretical interest. The misleading dualist idea of body and soul that has perverted our notions of mental life from the oldest times has led people to regard mental disorders as special phenomena, at one time directly as evil spirits that enter from without into the human body, at another time as mysterious dynamic occurrences affecting the mystic being of the soul (independently of the body). These dualistic and still wide-spread and mischievous errors have caused the most fatal mistakes in the treatment of mental disease; they have had the most unfortunate effect on juristic and social and other aspects of practical life. But the ground has been cut from under these irrational and superstitious ideas by modern psychiatry, which regards all mental disease as a disorder of the brain, and traces it to changes in the cortex that lie at the root of all psychoses (delusions, lunacy, etc.). As we call this central organ of mind the phronema, we may say: Psychiatry is the pathology and therapeutics of the phronema. In many disorders we have already succeeded in anatomically and chemically tracing the changes in the psychic or phronetal cells (the neurona in the phronema). These acquisitions of the pathological anatomy and physiology of the phronema have a great philosophic interest, because they throw a good deal of light on the monistic conception of psychic life. As the greater part (sixty to ninety per cent.) of these diseases are hereditary, and they have mostly been acquired gradually by the ancestors of the patient, they also afford clear proof of progressive heredity, or the inheritance of acquired characters.