Title: Monism as Connecting Religion and Science
Author: Ernst Haeckel
Release date: October 1, 2005 [eBook #9199]
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Language: English
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CONTENTS
The following lecture on Monism is an informal address delivered extemporaneously on October 9, 1892, at Altenburg, on the seventy-fifth anniversary of the "Naturforschende Gesellschaft des Osterlandes." The immediate occasion of it was a previous address delivered by Professor Schlesinger of Vienna on "Scientific Articles of Faith." This philosophical discourse contained, with reference to the weightiest and most important problems of scientific investigation, much that was indisputable; but it also contained some assertions that challenged immediate rejoinder and a statement of the opposite view. As I had for thirty years been very closely occupied with these problems of the philosophy of nature, and had set forth my convictions with respect to them in a number of writings, a wish was expressed by several members of the Congress that on this occasion I should give a summary account of these. It was in compliance with this wish that the following "Scientific Confession of Faith" was uttered. The substance of it, as written from recollection on the day after its delivery, first appeared in the Altenburger Zeitung of 19th October 1892. This was reproduced, with one or two philosophical additions, in the November number of the Freie Bühne für den Entwickelungskampf der Zeit (Berlin). In its present form the Altenburg address is considerably enlarged, and some parts have been more fully worked out. In the notes (p. 9 I) several burning questions of the present day have been dealt with from the monistic point of view.
The purpose of this candid confession of monistic faith is twofold. First, it is my desire to give expression to that rational view of the world which is being forced upon us with such logical rigour by the modern advancements in our knowledge of nature as a unity, a view in reality held by almost all unprejudiced and thinking men of science, although but few have the courage (or the need) to declare it openly. Secondly, I would fain establish thereby a bond between religion and science, and thus contribute to the adjustment of the antithesis so needlessly maintained between these, the two highest spheres in which the mind of man can exercise itself; in monism the ethical demands of the soul are satisfied, as well as the logical necessities of the understanding.
The rising flood of pamphlets and books published on this subject, demonstrates that such a natural union of faith and knowledge, such a reasonable reconciliation of the feelings and the reason, are daily becoming a more pressing necessity for the educated classes. In North America (in Chicago), there has been published for several years a weekly journal devoted to this purpose: The Open Court: A Weekly Journal devoted to the Work of Conciliating Religion and Science. Its worthy editor, Dr. Paul Carus (author of The Soul of Man, 1891), devotes also to the same task a quarterly journal under the title The Monist. It is in the highest degree desirable that so worthy endeavours to draw together the empirical and speculative views of nature, realism and idealism, should have more attention and encouragement than they have hitherto received, for it is only through a natural union of the two that we can approach a realisation of the highest aim of mental activity-the blending of religion and science in monism.
ERNST HAECKEL. JENA, October 31, 1892
A society for investigating nature and ascertaining truth cannot celebrate its commemoration day more fittingly than by a discussion of its highest general problems. It must be regarded, therefore, with satisfaction that the speaker on such an august occasion as this—the seventy-fifth anniversary of your Society—has selected as the subject of his address a theme of the highest general importance. Unfortunately, it is becoming more and more the custom on such occasions, and even at the general meetings of the great "Association of German Naturalists and Physicians," to take the subject of address from a narrow and specialised territory of restricted interest. If this growing custom is to be excused on the grounds of increasing division of labour and of diverging specialisation in all departments of work, it becomes all the more necessary that, on such anniversaries as the present, the attention of the audience should be invited to larger matters of common interest.
Such a topic, supreme in its importance, is that concerning "Scientific Articles of Faith," upon which Professor Schlesinger has already expounded his views.1 I am glad to be able to agree with him in many important points, but as to others I should like to express some hesitation, and to ask consideration for some views which do not coincide with his. At the outset, I am entirely at one with him as to that unifying conception of nature as a whole which we designate in a single word as Monism. By this we unambiguously express our conviction that there lives "one spirit in all things," and that the whole cognisable world is constituted, and has been developed, in accordance with one common fundamental law. We emphasise by it, in particular, the essential unity of inorganic and organic nature, the latter having been evolved from the former only at a relatively late period.2 We cannot draw a sharp line of distinction between these two great divisions of nature, any more than we can recognise an absolute distinction between the animal and the vegetable kingdom, or between the lower animals and man. Similarly, we regard the whole of human knowledge as a structural unity; in this sphere we refuse to accept the distinction usually drawn between the natural and the spiritual. The latter is only a part of the former (or vice versa); both are one. Our monistic view of the world belongs, therefore, to that group of philosophical systems which from other points of view have been designated also as mechanical or as pantheistic. However differently expressed in the philosophical systems of an Empedocles or a Lucretius, a Spinoza or a Giordano Bruno, a Lamarck or a David Strauss, the fundamental thought common to them all is ever that of the oneness of the cosmos, of the indissoluble connection between energy and matter, between mind and embodiment—or, as we may also say, between God and the world—to which Goethe, Germany's greatest poet and thinker, has given poetical expression in his Faust and in the wonderful series of poems entitled Gott und Welt.
That we may rightly appreciate what this Monism is, let us now, from a philosophico-historical point of view cast a comprehensive glance over the development in time of man's knowledge of nature. A long series of varied conceptions and stages of human culture here passes before our mental vision. At the lowest stage, the rude—we may say animal—phase of prehistoric primitive man, is the "ape-man," who, in the course of the tertiary period, has only to a limited degree raised himself above his immediate pithecoid ancestors, the anthropoid apes. Next come successive stages of the lowest and simplest kind of culture, such as only the rudest of still existing primitive peoples enable us in some measure to conceive. These "savages" are succeeded by peoples of a low civilisation, and from these again, by a long series of intermediate steps, we rise little by little to the more highly civilised nations. To these alone—of the twelve races of mankind only to the Mediterranean and Mongolian—are we indebted for what is usually called "universal history." This last, extending over somewhat less than six thousand years, represents a period of infinitesimal duration in the long millions of years of the organic world's development.
Neither of the primitive men we have spoken of, nor of those who immediately succeeded them, can we rightly predicate any knowledge of nature. The rude primitive child of nature at this lowest stage of development is as yet far from being the restless Ursachenthier (cause-seeking animal) of Lichtenberg; his demand for causes has not yet risen above that of apes and dogs; his curiosity has not yet mounted to pure desire of knowledge. If we must speak of "reason" in connection with pithecoid primitive man, it can only be in the same sense as that in which we use the expression with reference to those other most highly developed Mammals, and the same remark holds true of the first beginnings of religion.3
It is indeed still not infrequently the custom to deny absolutely to the lower animals reason and religion. An unprejudiced comparison, however, convinces us that this is wrong. The slow and gradual process towards completeness which, in the course of thousands of years, civilised life has been working in the soul of man, has not passed away without leaving some trace on the soul of our highest domestic animals also (above all, of dogs and horses). Constant association with man, and the steady influence of his training, have gradually, and by heredity, developed in their brain higher associations of ideas and a more perfect judgment. Drill has become instinct, an undeniable example of "the transmission of acquired characters."4
Comparative psychology teaches us to recognise a very long series of successive steps in the development of soul in the animal kingdom. But it is only in the most highly developed vertebrates-birds and mammals—that we discern the first beginnings of reason, the first traces of religious and ethical conduct. In them we find not only the social virtues common to all the higher socially-living animals,—neighbourly love, friendship, fidelity, self-sacrifice, etc.,—but also consciousness, sense of duty, and conscience; in relation to man their lord, the same obedience, the same submissiveness, and the same craving for protection, which primitive man in his turn shows towards his "gods." But in him, as in them, there is yet wanting that higher degree of consciousness and of reason, which strives after a knowledge of the surrounding world, and which marks the first beginning of philosophy or "wisdom." This last is the much later attainment of civilised races; slowly and gradually has it been built up from lower religious conceptions.
At all stages of primitive religion and early philosophy, man is as yet far removed from monistic ideas. In searching out the causes of phenomena, and exercising his understanding thereon, he is in the first instance prone in every case to regard personal beings—in fact, anthropomorphic deities—as the agents at work. In thunder and lightning, in storm and earthquake, in the circling of sun and moon, in every striking meteorological and geological occurrence, he sees the direct activity of a personal god or spirit, who is usually thought of in a more or less anthropomorphic way. Gods are distinguished as good and bad, friendly and hostile, preserving and destroying, angels and devils.
This becomes true in a yet higher degree when the advancing pursuit of knowledge begins to take into consideration the more complicated phenomena of organic life also, the appearance and disappearance of plants and animals, the life and death of man. The constitution of organised life, so suggestive as it is of art and purpose, leads one at once to compare it with the deliberately designed works of man, and thus the vague conception of a personal god becomes transformed into that of a creator working according to plan. As we know, this conception of organic creation as the artistic work of an anthropomorphic god—of a divine mechanic—generally maintained its ground almost everywhere, down even to the middle of our own century, in spite of the fact that eminent thinkers had demonstrated its untenability more than two thousand years ago. The last noteworthy scientist to defend and apply this idea was Louis Agassiz (died 1873). His notable Essay on Classification, 1857, developed that theosophy with logical vigour, and thereby reduced it to an absurdity.5
All these older religious and teleological conceptions, as well as the philosophical systems (such as those of Plato and of the Church fathers) which sprang from them, are antimonistic; they stand in direct antithesis to our monistic philosophy of nature. Most of them are dualistic, regarding God and the world, creator and creature, spirit and matter, as two completely separated substances. We find this express dualism also in most of the purer church-religions, especially in the three most important forms of monotheism which the three most renowned prophets of the eastern Mediterranean—Moses, Christ, and Mohammed—founded. But soon, in a number of impure varieties of these three religions, and yet more in the lower forms of paganism, the place of this dualism is taken by a philosophical pluralism, and over against the good and world-sustaining deity (Osiris, Ormuzd, Vishnu), there is placed a wicked and destroying god (Typhon, Ahriman, Siva). Numerous demi-gods or saints, good and bad, sons and daughters of the gods, are associated with these two chief deities, and take part with them in the administration and government of the cosmos.
In all these dualistic and pluralistic systems the fundamental idea is that of anthropomorphism, or the humanising of God; man himself, as godlike (or directly descended from God), occupies a special position in the world, and is separated by a great gulf from the rest of nature. Conjoined with this, for the most part, is the anthropocentric idea, the conviction that man is the central point of the universe, the last and highest final cause of creation, and that the rest of nature was created merely for the purpose of serving man. In the Middle Ages there was associated at the same time with this last conception the geocentric idea, according to which the earth as the abode of man was taken for the fixed middle point of the universe, round which sun, moon, and stars revolve. As Copernicus (1543) gave the death-blow to the geocentric dogma, so did Darwin (1859) to the anthropocentric one closely associated with it.6 A broad historical and critical comparison of religious and philosophical systems, as a whole, leads as a main result to the conclusion that every great advance in the direction of profounder knowledge has meant a breaking away from the traditional dualism (or pluralism) and an approach to monism. Ever more clearly are we compelled by reflection to recognise that God is not to be placed over against the material world as an external being, but must be placed as a "divine power" or "moving spirit" within the cosmos itself. Ever clearer does it become that all the wonderful phenomena of nature around us, organic as well as inorganic, are only various products of one and the same original force, various combinations of one and the same primitive matter. Ever more irresistibly is it borne in upon us that even the human soul is but an insignificant part of the all-embracing "world-soul"; just as the human body is only a small individual fraction of the great organised physical world.
The great general principles of theoretical physics and chemistry are now in a position to afford to this unifying conception of nature an exact, to a certain extent, indeed, a mathematical confirmation. In establishing the law of the "conservation of energy," Robert Mayer and Helmholtz showed that the energy of the universe is a constant unchangeable magnitude; if any energy whatever seems to vanish or to come anew into play, this is only due to the transformation of one form of energy into another. In the same way Lavoisier's law of the "conservation of matter" shows us that the material of the cosmos is a constant unchangeable magnitude; if any body seems to vanish (as, for example, by burning), or to come anew into being (as, for example, by crystallisation), this also is simply due to change of form or of combination. Both these great laws—in physics, the fundamental law of the conservation of energy, and in chemistry, of the conservation of matter—may be brought under one philosophical conception as the law of the conservation of substance; for, according to our monistic conception, energy and matter are inseparable, being only different inalienable manifestations of one single universal being-substance.7 In a certain sense we can regard the conception of "animated atoms" as essentially partaking of the nature of this pure monism—a very ancient idea which more than two thousand years ago Empedocles enunciated in his doctrine of "hate and love of the elements." Modern physics and chemistry have indeed in the main accepted the atomic hypothesis first enunciated by Democritus, in so far as they regard all bodies as built up of atoms, and reduce all changes to movements of these minutest-discrete particles. All these changes, however, in organic as well as in inorganic nature, become truly intelligible to us only if we conceive these atoms not as dead masses, but as living elementary particles endowed with the power of attraction and repulsion. "Pleasure" and "pain," and "love" and "hate," as predicates of atoms are only other expressions for this power of attraction and repulsion.
Although, however, monism is on the one hand for us an indispensable and fundamental conception in science, and although, on the other hand, it strives to carry back all phenomena, without exception, to the mechanism of the atom, we must nevertheless still admit that as yet we are by no means in a position to form any satisfactory conception of the exact nature of these atoms, and their relation to the general space-filling, universal ether. Chemistry long ago succeeded in reducing all the various natural substances to combinations of a relatively small number of elements; and the most recent advances of that science have now made it in the highest degree probable that these elements or the (as yet) irreducible primitive materials are themselves in turn only different combinations of a varying number of atoms of one single original element. But in all this we have not as yet obtained any further light as to the real nature of these original atoms or their primal energies.
A number of the acutest thinkers have, so far in vain, endeavoured to grapple more closely with this fundamental problem of the philosophy of nature, and to determine more exactly the nature of atoms as well as their relation to the space-filling ether. And the idea steadily gains ground that no such thing as empty space exists, and that everywhere the primitive atoms of ponderable matter or heavy "mass" are separated from each other by the homogeneous ether which extends throughout all space. This extremely light and attenuated (if not imponderable) ether causes, by its vibrations, all the phenomena of light and heat, electricity and magnetism. We can imagine it either as a continuous substance occupying the space between the mass-atoms, or as composed of separate particles; in the latter case we might perhaps attribute to these ether-atoms an inherent power of repulsion in contrast to the immanent attracting power of the heavy mass-atoms, and the whole mechanism of cosmic life would then be reducible to the attraction of the latter and the repulsion of the former. We might also place the "vibrations of the cosmic ether" alongside of the "operation of space in general," in the sense in which these words are used by Professor Schlesinger.
At any rate, theoretical physics has in recent years made an advance of fundamental importance and widest reach in our knowledge of nature, in that it has come nearer to a knowledge of this cosmic ether, and has forced the question of its essence, its structure, and its motion into the foreground of monistic nature-philosophy. Only a few years ago the cosmic ether was to the majority of scientists an imponderable something, of which, strictly speaking, absolutely nothing was known, and which could be admitted provisionally only as a precarious working hypothesis. All this was changed when Heinrich Hertz (1888) demonstrated the nature of electrical energy, by his beautiful experiments establishing the conjecture of Faraday that light and heat, electricity and magnetism, are closely related phenomena of one single set of forces, and depend on transverse vibrations of the ether. Light itself—whatever else it be—is always and everywhere an electrical phenomenon. The ether itself is no longer hypothetical; its existence can at any moment be demonstrated by electrical and optical experiment. We know the length of the light wave and the electric wave. Indeed, some physicists believe that they can even determine approximately the density of ether. If by means of the airpump we remove from a bell-jar the atmospheric air (except an insignificant residue), the quantity of light within it remains unchanged; it is the vibrating ether we see.9 These advances in our knowledge of the ether mean an immense gain for monistic philosophy. For they do away with the erroneous ideas of empty space and actio in distans; the whole of infinite space, in so far as it is not occupied by mass-atoms ("ponderable matter"), is filled by the ether. Our ideas of space and time are quite other than those taught by Kant a hundred years ago; the "critical" system of the great Koenigsberg philosopher exhibits in this respect, as well as in his teleological view of the organic world and in his metaphysics, dogmatic weaknesses of the most pronounced kind.8 And religion itself, in its reasonable forms, can take over the ether theory as an article of faith, bringing into contradistinction the mobile cosmic ether as creating divinity, and the inert heavy mass as material of creation. From this successfully scaled height of monistic knowledge there open up before our joyously quickened spirit of research and discovery new and surprising prospects, which promise to bring us still nearer to the solution of the one great riddle of the world. What is the relation of this light mobile cosmic ether to the heavy inert "mass," to the ponderable matter which we chemically investigate, and which we can only think of as constituted of atoms? Our modern analytical chemistry remains for the present at a standstill, in presence of some seventy irreducible elements, or so-called primary substances. But the reciprocal relation of these elements, the affinity of their combinations, their spectroscopic behaviour, and so forth, make it in the highest degree probable that they are all merely historical products of an evolutionary process, having their origin in various dispositions and combinations of a varying number of original atoms.
To these original or mass-atoms—the ultimate discrete particles of inert "ponderable matter"—we can with more or less probability ascribe a number of eternal and inalienable fundamental attributes; they are probably everywhere in space, of like magnitude and constitution. Although possessing a definite finite magnitude, they are, by virtue of their very nature, indivisible. Their shape we may take to be spherical; they are inert (in the physical sense), unchangeable, inelastic, and impenetrable by the ether. Apart from the attribute of inertia, the most important characteristic of these ultimate atoms is their chemical affinity—their tendency to apply themselves to one another and combine into small groups in an orderly fashion. These fixed groups (fixed, that is to say, under the present physical conditions of existence of the earth) of primitive atoms are the atoms of the elements—the well-known "indivisible" atoms of chemistry. The qualitative, and, so far as our present empirical knowledge goes, unchangeable distinctions of our chemical elements are therefore solely conditioned by the varying number and disposition of the similar primitive atoms of which they are composed. Thus, for example, the atom of carbon (the real "maker" of the organic world) is in all probability a tetrahedron made up of four primitive atoms.
After Mendelejeff and Lothar Meyer had discovered (1869) the "periodic law" of the chemical elements, and founded on it a "natural system" of these elements, this important advance in theoretical chemistry was subsequently put to profitable use by Gustav Wendt from an evolutionary point of view. He endeavoured to show that the various elements are products of evolution or of historically originating combinations of seven primary elements, and that these last again are historical products of one single primitive element This hypothetical original matter had been already designated by Crookes, in his Genesis of the Elements, as primary material or protyl.10 The empirical proof of the existence of this original matter lying at the foundation of all ponderable material is perhaps only a question of time. Its discovery would probably realise the alchemists' hope of being able to produce gold and silver artificially out of other elements. But then arises the other great question: "How is this primary mass related to the cosmic ether? Do these two original substances stand in fundamental and eternal antithesis to one another? Or was it the mobile ether itself, perhaps, that originally engendered the heavy mass?"11
In answer to this great and fundamental question, various physical hypotheses have been put forward. But, like the various atomic theories of chemistry, they have not as yet been clearly established, and the same appears to me to be the case also with the ingenious hypothesis which the lecturer has unfolded to us with reference to the Influence of Space. As he himself rightly says, in all these endeavours after a philosophy of nature we are still, for the present, dealing with "scientific articles of faith," concerning the validity of which different persons, according to their subjective judgment and stage of culture, may have widely divergent views. I believe that the solution of these fundamental questions still lies as yet beyond the limits of our knowledge of nature, and that we shall be obliged, for a long time yet to come, to content ourselves with an "Ignoramus"—if not even with an "Ignorabimus."
The case is very different, however, if we turn from these atomistic element hypotheses and direct our attention to the historical conditions of the evolution of the world, as these have been revealed to us by the magnificent advances in our knowledge of nature which have been made within the last thirty years. An immense new territory has here been opened up to us in the realms of knowledge—a territory in which a series of most important problems, formerly held to be insoluble, has been answered in the most surprising manner.12
Among the triumphs of the human mind the modern doctrine of evolution takes a foremost place. Guessed at by Goethe a hundred years ago, but not expressed in definite form until formulated by Lamarck in the beginning of the present century, it was at last, thirty years ago, decisively established by Charles Darwin, his theory of selection filling up the gap which Lamarck in his doctrine of the reciprocal influence of heredity and adaptation had left open. We now definitely know that the organic world on our earth has been as continuously developed, "in accordance with eternal iron laws," as Lyell had in 1830 shown to be the case for the inorganic frame of the earth itself; we know that the innumerable varieties of animals and plants which during the course of millions of years have peopled our planet are all simply branches of one single genealogical tree; we know that the human race itself forms only one of the newest, highest, and most perfect offshoots from the race of the Vertebrates.
An unbroken series of natural events, following an orderly course of evolution according to fixed laws, now leads the reflecting human spirit through long aeons from a primeval chaos to the present "order of the cosmos." At the outset there is nothing in infinite space but mobile elastic ether, and innumerable similar separate particles—the primitive atoms—scattered throughout it in the form of dust; perhaps these are themselves originally "points of condensation" of the vibrating "substance," the remainder of which constitutes the ether. The atoms of our elements arise from the grouping together in definite numbers of the primitive atoms or atoms of mass. As the Kant-Laplace nebular hypothesis has it, the rotating heavenly bodies separate themselves out from that vibrating primeval cloud. A single unit among many thousands of celestial bodies is our sun, with its planets, which originated by being centrifugally thrown off from it. Our insignificant earth is a single planet of our solar system; its entire individual life is a product of the sunlight. After the glowing sphere of the earth has cooled down to a certain degree, drops of fluid water precipitate themselves on the hardened crust of its surface—the first preliminary condition of organic life. Carbon atoms begin their organism-engendering activity, and unite with the other elements into plasma-combinations capable of growing. One small plasma-group oversteps the limits of cohesion and individual growth; it falls asunder into two similar halves. With this first moneron begins organic life and its most distinctive function, heredity. In the homogeneous plasma of the monera, a firmer central nucleus is separated from a softer outer mass; through this differentiation of nucleus and protoplasm arises the first organic cell. For a long time our planet was inhabited solely by such Protista or single-celled primitive creatures. From coenobia or social unions of these afterwards arose the lowest histones, multicellular plants and animals.
By the sure help of the three great empirical "records of creation," palaeontology, comparative anatomy, and ontogeny, the history of descent now leads us on step by step from the oldest Metazoa, the simplest pluricellular animals, up to man.13 At the lowest root of the common genealogy of the Metazoa stand the Gastraeadae and Spongidae; their whole body consists, in the simplest case, solely of a round digestive sac, the thin wall of which is formed by two layers of cells—the two primitive germinal layers. A corresponding germinal condition, the two-layered gastrula, occurs transitorily in the embryological history of all the other Metazoa, from the lowest Cnidaria and Vermes up to man. From the common stock of the Helminthes, or simple worms, there develop as independent main branches the four separate stems of the Molluscs, Star-fishes, Arthropods, and Vertebrates. It is only these last whose bodily structure and development in all essential respects coincide with those of man. A long series of lower aquatic Vertebrates (lancelets, lampreys, fishes) precedes the lungbreathing Amphibians, which appear for the first time in the Carboniferous period. The Amphibians are followed in the Permian period by the first Amniota, the oldest reptiles; from these develop later, in the Triassic period, the Birds on the one hand, and the Mammals on the other. That man in his whole bodily frame is a true mammal, becomes obvious as soon as the natural unity of this highest class of animals is recognised. The simplest comparison must have convinced the unprejudiced observer of the close constitutional relationship between man and the ape, which of all the Mammals comes nearest him. Comparative anatomy, with its deeper vision, showed that all differences in bodily structure between man and the Anthropoidea (gorilla, chimpanzee, orang) are less important than the corresponding differences in bodily structure between these anthropoid apes and the lower apes. The phylogenetic significance of this fact, first emphasised by Huxley, is quite clear. The great question of the origin of the human race, or of "man's place in Nature," the "question of all questions," was then scientifically answered: "Man is descended from a series of ape-like Mammals." The descent of man (anthropogeny) discloses the long series of vertebrate ancestors, which preceded the late origin of this, its most highly developed offshoot.
The incalculable importance of the light cast over the whole field of human knowledge of nature by these results is patent to everyone. They are destined every year increasingly to manifest their transforming influence in all departments of knowledge, the more the conviction of their irrefragable truth forces its way. And it is only the ignorant or narrow-minded who can now doubt their truth. If, indeed, here and there, one of the older naturalists still disputes, the foundation on which they rest, or demands proofs which are wanting (as happened a few weeks ago on the part of a famous German pathologist at the Anthropological Congress in Moscow), he only shows by this that he has remained a stranger to the stupendous advances of recent biology, and above all of anthropogeny. The whole literature of modern biology, the whole of our present zoology and botany, morphology and physiology, anthropology and psychology, are pervaded and fertilised by the theory of descent.14
Just as the natural doctrine of development on a monistic basis has cleared up and elucidated the whole field of natural phenomena in their physical aspect, it has also modified that of the phenomena of mind, which is inseparably connected with the other. Our human body has been built up slowly and by degrees from a long series of vertebrate ancestors, and this is also true of our soul; as a function of our brain it has gradually been developed in reciprocal action and re-action with this its bodily organ. What we briefly designate as the "human soul," is only the sum of our feeling, willing, and thinking—the sum of those physiological functions whose elementary organs are constituted by the microscopic ganglion-cells of our brain. Comparative anatomy and ontogeny show us how the wonderful structure of this last, the organ of our human soul, has in the course of millions of years been gradually built up from the brains of higher and lower vertebrates. Comparative psychology teaches us how, hand in hand therewith, the soul itself, as function of the brain, has been developed. The last-named science teaches us also that a primitive form of soul-activity is already present even in the lowest animals, the single-celled primitive animals, Infusoria and Rhizopoda. Every scientific man who has long observed the life-activity of these single-celled Protista, is positively convinced that they also possess a soul; that this "cell-soul" also consists of a sum of sensations, perceptions, and volitions; the feeling, thinking, and willing of our human soul differ from these only in degree. In like manner there is present in the egg-cell (as potential energy) a hereditary cell-soul, out of which man, like every other animal, is developed.15
The first task of a truly scientific psychology will therefore be, not, as hitherto, idle speculation about an independent immaterial soul-existence and its puzzling temporary connection with the animal body, but rather the comparative investigation of the organs of the soul and the experimental examination of their psychical functions. For scientific psychology is a part of physiology, the doctrine of the functions and the life-activities of organisms. The psychology and psychiatry of the future, like the physiology and pathology of to-day, must take the form of a cellular study, and in the first instance investigate the soul-functions of the cells. Max Verworn, in his fine Psycho-physiological Protistastudies, has lately shown us what important disclosures such a cellular psychology can make, even in dealing with the lowest grades of organic life, in the single-celled Protista (especially Rhizopoda and Infusoria).
These same main divisions of soul-activity, which are to be met with in the single-celled organism,—the phenomena of irritability, sensation, and motion,—can be shown to exist in all multicellular organisms as functions of the cells of which their bodies are composed. In the lowest Metazoa, the invertebrate sponges and polyps, there are, just as in plants, no special soul-organs developed, and all the cells of the body participate more or less in the "soul-life." It is only in the higher animals that the soul-life is found to be localised and connected with special organs. As a consequence of division of labour, there have here been developed various sense-organs as organs of specific sensibility, muscles as organs of motion and volition, nerve-centres or ganglia as central co-ordinating and regulating organs. In the most highly developed families of the animal kingdom, these last come more and more into the foreground as independent soul-organs. In correspondence with the extraordinarily complicated structure of their central nervous system (the brain with its wonderful complex of ganglion-cells and nerve-fibres), the many-sided activity of such animals attains a wonderful degree of development.
It is only in these most highly-developed groups of the animal kingdom that we can with certainty establish the existence of those most perfect operations of the central nervous system, which we designate as consciousness. As we know, it is precisely this highest brain-function that still continues to be looked upon as a completely enigmatical phenomenon, and as the best proof for the immaterial existence of an immortal soul. It is usual at the same time to appeal to Du Bois-Reymond's well-known "Ignorabimus address on the Boundaries of Natural Knowledge" (1872). It was by a peculiar irony of fate that the famous lecturer of the Berlin Academy of Science, in this much-discussed address of twenty years ago, should be representing consciousness as an incomprehensible marvel, and as presenting an insuperable barrier to further advances of knowledge, at the very moment that David Friedrich Strauss, the greatest theologian of our century, was showing it to be the opposite. The clear-sighted author of The Old Faith and the New had already clearly perceived that the soul-activities of man, and therefore also his consciousness, as functions of the central nervous system, all spring from a common source, and, from a monistic point of view, come under the same category. The "exact" Berlin physiologist shut this knowledge out from his mind, and, with a short-sightedness almost inconceivable, placed this special neurological question alongside of the one great "world-riddle," the fundamental question of substance, the general question of the connection between matter and energy.16
As I long ago pointed out, these two great questions are not two separate "world-riddles." The neurological problem of consciousness is only a special case of the all comprehending cosmological problem, the question of substance. "If we understood the nature of matter and energy, we should also understand how the substance underlying them can under certain conditions feel, desire, and think." Consciousness, like feeling and willing, among the higher animals is a mechanical work of the ganglion-cells, and as such must be carried back to chemical and physical events in the plasma of these. And by the employment of the genetic and comparative method we reach the conviction that consciousness, and consequently reason also, is not a brain-function exclusively peculiar to man; it occurs also in many of the higher animals, not in Vertebrates only, but even in Articulates. Only in degree, through a higher stage of cultivation, does the consciousness of man differ from that of the more perfect lower animals, and the same is true of all other activities of the human soul.
By these and other results of comparative physiology our whole psychology is placed on a new and firm monistic basis. The older mystical conception of the soul, as we find it amongst primitive peoples, but also in the systems of the dualistic philosophers of to-day, is refuted by them. According to these systems, the soul of man (and of the higher animals) is a separate entity, which inhabits and rules the body only during its individual life, but leaves it at death. The widespread "piano-theory" (Claviertheorie) compares the "immortal soul" to a pianist who executes an interesting piece—the individual life—on the instrument of the mortal body, but at death withdraws into the other world. This "immortal soul" is usually represented as an immaterial being; but in fact it is really thought of as quite material, only as a finer invisible being, aerial or gaseous, or as resembling the mobile, light, and thin substance of the ether, as conceived by modern physics. The same is true also for most of the conceptions which rude primitive peoples and the uneducated classes among the civilised races have, for thousands of years, cherished as to spectral "ghosts" and "gods." Serious reflection on the matter shows that here—as in modern spiritualism—it is not with really immaterial beings, but with gaseous, invisible bodies, that we are dealing. And further, we are utterly incapable of imagining a truly immaterial being. As Goethe clearly said, "matter can never exist or act apart from spirit, neither can spirit apart from matter."
As regards immortality, it is well known that this important idea is interpreted and applied in a great variety of ways. It is often made a reproach against our Monism that it altogether denies immortality; this, however, is erroneous. Rather do we hold it, in a strictly scientific sense, as an indispensable fundamental conception of our monistic philosophy of nature. Immortality in a scientific sense is conservation of substance, therefore the same as conservation of energy as defined by physics, or conservation of matter as defined by chemistry. The cosmos as a whole is immortal. It is just as inconceivable that any of the atoms of our brain or of the energies of our spirit should vanish out of the world, as that any other particle of matter or energy could do so. At our death there disappears only the individual form in which the nerve-substance was fashioned, and the personal "soul" which represented the work performed by this. The complicated chemical combinations of that nervous mass pass over into other combinations by decomposition, and the kinetic energy produced by them is transformed into other forms of motion.