Popular Science Monthly/Volume 61/September 1902/The World-View of a Scientist: Ernst Haeckel's Philosophy

by Frank Thilly

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THE WORLD-VIEW OF A SCIENTIST: ERNST HAECKEL'S PHILOSOPHY.^[1]

By Professor FRANK THILLY,

UNIVERSITY OF MISSOURI.

IN 1892 Ernst Haeckel, the celebrated biologist, delivered an address before a society of naturalists, in which he outlined his creed, his 'Glaubensbekenntniss eines Naturforschers.' This address was printed under the title 'Monism as a Bond between Religion and Science' and is now in its tenth edition. In 1899 a more elaborate account of Haeckel's philosophy was given to the world in a book called 'The World Riddles.' Within a few weeks after the appearance of this work 10,000 copies has been sold. It was at once translated into English and figured prominently in the lists of the most popular books of the day in our country. The magazines and even daily papers have published review after review of the 'World Riddles'; pamphlets and books have been written about it, and the interest still continues.^[2] The Academy of Turin, Italy, has declared the 'World Riddles,' to be the best book written during the last four years of the nineteenth century, and has awarded to its author the Bressa prize of 10,000 lire. The work has raised the feelings of many usually tranquil persons to a higher pitch of excitement, provoking extravagant expressions of admiration from some, and words of passionate indignation from others. There is joy in the camp of the Haeckelites, where the author is glorified as the greatest philosopher of the age, while in the ranks of the opponents there is angry contempt for a man who, so it is said, is an absolute ignoramus in matters of philosophy and in everything outside of his own Fach, and some critics are even willing to call in question his standing as a biologist. The turmoil is increasing, the angry voices are growing louder, and we hear words of reproach and insult on both sides, which we are not accustomed to hear from the lips of men of science. Some of the attacks which have been made upon Haeckel have passed the bounds of the respectable. One fire-eater, a Christian theologian, has taken the matter so to heart as to make an entirely personal affair of it. 'My remarks,' he says, 'are an attack upon Haeckel's honor, and are intended as such.'^[3] The conflicts between the realists and nominalists during the middle ages could not have been more bitter than this Haeckel controversy threatens to become, and we need have no fear, so far as I can see, that the occupation with intellectual things is blunting the emotional side of the modern thinker's soul.

It is not my intention to join in the hue and cry against this man who has dared to offer the world a Weltanschauung, nor am I willing to stamp his work as unworthy of notice. It is true, Haeckel has provoked a fair share of the abuse that has been heaped upon him by his own intolerant attitude, but after all two wrongs do not make a right. I believe that it will be worth our while to hear patiently what Haeckel has to say, and then to subject his philosophy to the tests by which it will be judged at last when the discordant voices of the present are hushed and the author and his critics are sleeping in their quiet graves. A work that has made such an impression upon an age as the 'World Riddles' can not be ignored or thrown out of court without a hearing, and the hearing must be impartial and temperate, such a hearing as it is bound to receive at the bar of history. It expresses the views of large numbers of natural scientists to-day, although few would dare to make public confession of their faith, as the fearless Jena biologist has done; and as an expression of opinion coming from such a quarter, it deserves attention. I shall therefore try in what follows to give an exposition of Haeckel's thought, and to examine its value as a theory of the universe.

And first let us turn to our philosopher's theory of knowledge.^[4] Our true knowledge, he says, is real in its nature; it consists of ideas (Vorstellungen) which correspond to really existing things. It is true we cannot know the innermost essence of this real world, of the thing in itself,^[5] but we are convinced by impartial and critical observation and comparison that the external world makes the same impressions upon the sense-organs and brain of all normal rational individuals, and that the same ideas are formed by all persons whose organs of thought function normally. All our knowledge depends upon two physiological functions—upon sensation and upon the combination of the impressions thus gained, by association. The experiences which we receive from the external world through our sense-organs and sense-centers in the brain are transformed into ideas by other brain-centers, and these are combined into inferences by association. These inferences are both inductive and deductive, processes which have equal value. Other complicated brain operations, the formation of chains of reasoning, abstraction and conception, imagination, consciousness, thought and philosophy, are all functions of the ganglionic cells of the cerebral cortex.^[6]

But our sense-activity is limited; we can discover only a part of the qualities possessed by the objects of the external world. The civilized man transforms his sense-impressions into specific sensations in the sense-centers of the cortex, and combines these by association in the thought-centers into ideas or presentations, and by further combination of the idea-groups he finally reaches connected knowledge. But this knowledge always remains unsatisfactory, unless the fancy supplements the insufficient combining power of the understanding and by association of memory-images combines remote cognitions into a connected whole. In this way new ideas arise which alone explain the perceived facts and satisfy the causal need of the reason.

The ideas which fill the gaps in our knowledge, or take its place, we may call belief (Glaube). We are forced to belief in science. We surmise or assume that a certain relation exists between two phenomena although we do not know it with certainty. In the case of knowledge of causes we form a hypothesis. But only such hypotheses can be admitted in science which do not contradict known facts, e. g., in physics, the doctrine of ether-vibrations; in chemistry, the assumption of atoms and their affinity; in biology, the doctrine of the molecular structure of the living plasma.

The explanation of a larger series of connected phenomena by the assumption of a common cause we call a theory. Here, too, faith or belief in the scientific sense is indispensable, here, too, the poetic fancy fills the gap which the understanding leaves in the knowledge of things. A theory can therefore be regarded only as an approximation to truth; it can always be supplanted by a better theory. But theory is indispensable in science, for theory alone explains the facts by assuming causes. Hence whoever wishes to do entirely without theory and to construct pure science upon nothing but 'certain facts' relinquishes all knowledge of causes and the satisfaction of the causal need of the reason.^[7] Examples of such theories are the theory of gravitation, the cosmological nebular theory, the principle of energy, the atomic theory, the vibration theory, the cell theory, the theory of descent. They explain a system of natural phenomena by assuming a common cause for all the particular facts of their territory. This cause itself may be unknown in its essence or be a merely provisional hypothesis. Gravitation, energy itself, ether, the atom, heredity, may be regarded by sceptical philosophers as 'mere hypotheses,' as products of scientific belief, but they are indispensable until they are replaced by a better hypothesis.

This theory of knowledge is almost identical with that offered by Epicurus three centuries before Christ. With respect to the problem of the origin of knowledge it is an extremely naïve form of empiricism and associationism. It is the old naïve story about sensations putting themselves together and forming ideas, of ideas putting themselves together and forming thought, personality, and all the other higher processes of consciousness.^[8] It is true Haeckel does incidentally speak of innate knowledge à priori in connection with innate instincts, which he explains as having originally been acquired empirically through raceexperience,^[9] but, so far as I see, this view does not affect his theory. Haeckel's empiricism is as unsatisfactory as it is simple, and has about as much value as the old theory of creation has in Haeckel's own science. Kant and modern epistemology seem to have made no impression whatever upon the great German biologist.

With respect to the problem of the nature of knowledge Haeckel's position is somewhat vacillating. He tells us that we do not know the irmer essence of things in themselves; indeed, he afterwards hints that perhaps there are no such things in themselves for all we know. At the same time space and time are realities, objective realities, real entities: the existence of space and time is now definitely proved.^[10] Here we seem to get a jumble of nearly all possible standpoints, of realism, semirealism and idealism—one after another. That is (1) there is a thing in itself; we do not know its essence, however, but only its effects upon us; (2) for all we know there may be no thing in itself, we do not know and we do not care, we can get along without it; (3) space and time are realities, that is, either things in themselves or the attributes of things in themselves.

The same uncertainty prevails with respect to another point. Haeckel is a dogmatist and sceptic by turns, as the occasion suits him. We cannot know everything with certainty, we cannot get along without faith in science. The theories of science are articles of faith, provisional assumptions which may be overthrown at any time. Among such hypotheses Haeckel enumerates nearly all the great theories of the different sciences and also his own philosophical system^[11] But this humility is merely a passing stage with our philosopher; his attitude is generally dogmatic; the tone of his book is that of a man who is absolutely sure of his result. Thus after having told us that certainty is impossible in science, that we must fill the gaps in our knowledge by faith, he declares dogmatically that the existence of ether, cosmo-ether, as real matter, is to-day a positive fact and not a mere hypothesis. ^[12] We can prove its existence by electrical and optical experiments; indeed, we can see the vibrating ether.^[13] It is likewise a certain historical fact that man is descended from apes, etc.^[14] The discovery of the fossil ape-man of Java proves conclusively the descent of man from the ape.^[15] The existence of space and time is also definitely proved. The historical evolution of the human soul from a long series of higher and lower mammalian souls must be regarded as a scientifically proved fact.

We are now ready to take up Haeckel's metaphysics. We shall first discuss the principles upon which his entire system rests and then consider their application to inorganic nature, organic nature and the psychical world.

In the celebrated address which Du Bois-Reymond delivered in the year 1880, and which was afterwards published as the 'Seven World Biddies,' he proposed seven problems: (1) The essence of matter and energy; (2) the origin of motion; (3) the origin of life; (4) the apparently purposive arrangement of nature; (5) the origin of sensation and consciousness; (6) rational thought and the origin of language; (7) the question of free will. Questions 1, 2 and 5 he regards as impossible of solution or transcendent; 3, 4 and 6 are difficult, but can be solved. On question 7 he is undecided. Haeckel makes short work of these riddles. The problem of matter and energy, the problem of motion and the problem of consciousness are solved, he thinks, by his conception of substance; the problem of life, the teleological problem and the problem of reason by the modern theory of evolution, while the free will problem is no problem at all, but a dogma based on mere illusion.

The conception of substance is therefore Haeckel's fundamental principle. Let us see what it means. There is one underlying prin- are two different aspects.^[16] This substance is infinite, indestructible and eternal; it fills the infinite space and is in eternal motion. The matter and energy therefore in the universe are constant. This gives us the laws of the conservation of matter and of energy, which really form one single law, the law of substance, the cosmological ground law, the law of the constancy of the universe, which follows necessarily from the principle of causality. This universal substance reveals to us two different aspects, two fundamental attributes: matter, the infinite extended substance-stuff, and mind (Geist), the all-embracing substance-energy. It is God and nature at the same time; body and mind (or matter and energy) are inseparably connected.^[17] God is not an external being, acting from without, but a divine power or moving spirit, the cosmos itself; the phenomena of surrounding nature, organic as well as inorganic, are merely different products of one and the same original force, different combinations of one and the same original matter.^[18] All the individual objects in the world, all the individual forms of existence, are merely transitory forms of the substance, accidents or modes. These modes are corporeal things, material bodies, when we consider them under the attribute of extension (as filling space); forces or ideas, when we regard them under the attribute of thought (or 'energy'). Matter (the stuff filling space) and energy (the moving force) are two attributes of one substance.^[19]

This view Haeckel calls monism, and tries to distinguish from materialism as follows: (1) Our pure monism is neither identical with theoretical materialism, which denies mind and resolves the world into a sum of dead atoms, nor with theoretical spiritualism (recently termed Energetik by Ostwald), which denies matter and regards the world as a spatially arranged group of energies or immaterial natural forces. (2) Matter can never exist and act without mind, nor mind without matter. 'We adhere to the pure and unambiguous monism of Spinoza,' says Haeckel; 'matter, as the infinitely extended substance, and mind (or energy) as the sentient (empfindend) or thinking substance, are the two fundamental attributes or ground properties of the all-embracing divine world-being, the universal substance.'^[20]

If we interpret Haeckel's system in the light of the preceding statements, we certainly reach a kind of monism. Mind and matter are both aspects of an underlying substance. There is no difficulty in understanding what Haeckel means by the material aspect of the substance: it is the space-filling, extended stuff. It is not so easy to see, however, what the other phase of substance, the mental aspect, is. This attribute the philosopher calls mind or Geist, thought, the sentient side, energy, the moving force. In the chapter on substance we are left under the impression that these attributes are not independent entities, but attributes of something behind them, of a thing in itself called the substance. This impression is strengthened by Haeckel's concluding reflections at the end of his book:

We confess at the outset that we know just as little of the innermost essence of nature to-day, as did Anaximander and Empedocles 2,400 years ago, Spinoza and Newton 200 years ago, or Kant and Goethe 100 years ago. Yes, we must even confess that the real essence of the substance becomes more wonderful and mysterious the more deeply we penetrate into the knowledge of its attributes, matter and energy, the more thoroughly we become acquainted with its numberless manifestations and their evolution. What is behind the knowable phenomena as a 'thing in itself' we do not know even to this day. But remaining true to his general tendency to be inconsistent with himself our author goes on to say: But what do we care about this mystical 'thing in itself' anyhow, when we have no means of investigating it, when we do not even know clearly whether it exists or not. Let us therefore leave it to the 'pure metaphysicians 'to ponder fruitlessly over this ideal ghost, and let us rejoice instead as 'true physicists' in the enormous advances which our monistic philosophy of nature has actually made.^[21]

We see, Haeckel's conception of substance changes like a chameleon before our very eyes. We are first told that there is a thing in itself, then that we do not know what it is, and finally that we do not even know that it is. We are naïvely told that the notion of substance will solve all riddles, make all things clear to us, then we are informed that it is a mystery, the greatest mystery of all, and finally it vanishes into thin air before our very gaze, and turns into a phantom which perhaps does not even exist. After making the conception of substance do service as a principle of explanation for 436 pages of his book, after having employed it as the support of real attributes, space, time and energy, Haeckel suddenly dismisses it as an utterly useless piece of metaphysical furniture.

But these are not the only inconsistencies in the doctrine of substance. We are told that substance is unknowable, that matter and force are its attributes. We are told that God, the thing in itself, is an intramundane being and acts in the substance as force or energy.^[22] That is, the thing in itself is force. Yes, perhaps the original hypothetical chemical element, the prothyl, is the substance;^[23] perhaps the world-ether is the creating god-head.^[24] What does all this mean? The substance perhaps does not exist; the substance does exist, but is unknowable; the substance has real attributes, and we know them; the substance is energy; the substance is perhaps prothyl; the substance is perhaps the world-ether. Haeckel is certainly right in his remark that consistent thinking is a difficult business.

There is another point worth noting at this place which will come up again. Haeckel speaks of the mental aspect of the substance as mind, thought, sensation (Empfindung), energy, moving force. This is something like Schopenhauer's will, only that it is not a substance, but the attribute of a substance. As an attribute distinct from the other attribute, matter, it must be immaterial, something of the same nature as consciousness, only not conscious on the lower stages of existence. It seems to account for all movement and thought in the world.

Now that we have become acquainted with Haeckel's fundamental principles, let us observe what application is made of them. We shall take up in order the inorganic world, organic nature and psychic life.

The substance fills infinite space as a continuum. It is endowed with a mechanical form of activity, with a striving (Streben) to become dense or to contract. In this way little centers are formed of the parts of the universal substance which Haeckel calls pyknatoms, and which possess sensation (Empfindung) and impulse or striving (Streben), will-movements of the simplest kind, and hence are in a certain sense animated.^[25] The atoms are not dead mass particles, but living elemental particles, endowed with the power of attraction and repulsion; love and hate are merely different expressions for this power of attraction and repulsion,^[26] These original atoms are probably of the same size and essence, but they are not divisible. Their form is most likely spherical; they are inert (in the sense of physics), unchangeable, inelastic, not penetrable by ether. They have another quality, chemical affinity, an inclination to combine and to form little groups in a uniform way. These fixed groups of original atoms are the so-called elemental atoms, the known indecomposable atoms of chemistry. Hence the qualitative differences of our chemical elements are conditioned solely by the different number and configuration of the homogeneous original atoms. We do not know what is the nature of these original atoms themselves; perhaps it is prothyl.^[27]

These atoms do not float in empty space, but in a continuous extremely thin intervening substance which represents the non-contracted part of the original substance. In this way the substance, which in its original state of rest has the same density throughout, differentiates into two parts: the pyknatoms, ponderable matter, and the intervening ether, the imponderable matter. The result of this separation or differentiation is a constant struggle between these antagonistic parts of substance, and to this struggle all physical processes are due. As was said before, these atoms are not dead and movable by external forces only; they possess sensation and will (in the lowest degrees, of course), they experience pleasure in the process of contraction (Verdichtung), pain in the process of tension (Spannung); they strive after the first and struggle against the last. Hence atoms are endowed with a universal 'soul' of the most primitive kind. The same is true of molecules or mass-particles, which consist of two or more atoms.^[28] But these elementary psychical activities which are attributed to the atoms are unconscious processes. Consciousness and soul-life are not identical terms; consciousness forms but a part of soulphenomena; the largest part of the latter is unconscious,^[29] There is no immaterial substance; experience never reveals such a thing, no force that is not bound to matter, no form of energy that is not mediated by movements of matter.

There is no difference between organic and inorganic nature. All phenomena are explained by physico-chemical forces in each realm. The doctrine of the vitalists is absurd. The peculiar chemical-physical properties of carbon—particularly of the carbon compounds—are the mechanical causes of the peculiar movements which distinguish the organic from the inorganic world. Life, in other words, is the product of inorganic nature, the living plasm originated from inorganic carbon compounds,^[30] The universe is a unity, all natural forces are one. All the phenomena of organic life are subject to the universal law of substance, as much so as inorganic phenomena.

The higher forms of life are developed from the lower in accordance with the principles of the theory of evolution as advanced by Darwin. That man is descended from the higher apes is now an absolutely proved fact. The idea of purpose, the teleological explanation, which was eliminated from physical science long ago, can not be accepted in biology. The theory of natural selection proposed by Darwin explains the origin of so-called purposive organisms by purely mechanical causes. There is no purposive impulse discoverable anywhere in organic life; everything is the necessary result of the struggle for existence, which acts as a blind regulator and not as a foreseeing God, and which causes the transformation of organic forms by the reciprocal action of the laws of heredity and adaptation. Nor is there any such purposiveness in our moral life or in history, individual or racial. Mechanical causality explains everything.

We turn now to Haeckel's philosophy of soul, to which he devotes one third of the entire space of the 'Weltraethsel.'^[31] The soul is a natural phenomenon; hence psychology is a branch of natural science, particularly of physiology. The so-called psychologists are ignorant of anatomy and physiology, hence the largest part of psychological literature is to-day worthless waste paper. The prevalent conception of soul life regards soul and bod)' as two different beings, says Haeckel, and this view has nothing to stand on. Soul life is a sum total of vital phenomena which are like all others bound to a definite material substratum called the psychoplasm.^[32] In this sense our view is materialistic. The processes in the lower forms of soul life, excitability, reflex movement, sensibility (Empfindlichkeit) and the impulse of self-preservation are directly conditioned by physiological processes in the plasm of their cells, by physical and chemical changes, which may be explained partly by heredity, partly by adaptation. The same may be said of the higher forms of soul life, for they have developed from the lower forms.

A study of comparative psychology and folk psychology, of ontogenetic and phylogenetic psychology, will show that organic life, in all its gradations, develops from the same forces of nature, from the physiological functions of sensation and movement. The plasm is the indispensable bearer of the psyche. The psyche, or soul, is not a separate being; the term psyche or soul is a collective term for the sum-total of the psychic functions of the plasm. In this sense the soul is a physiological abstraction, like the concept metabolism or generation. The 'soul' can not function without a certain chemical and physical composition of the psychoplasm.

All living organisms are sensitive (empfindlich); they distinguish the states of the surrounding world and react upon the same by certain changes within themselves. Light, heat, mechanical and chemical processes in the environment, act as stimuli upon the sensitive psychoplasm and cause changes in its molecular composition. There is an ascending scale of soul life, from the simplest forms of organic life where the entire protoplasm is sensitive and reacts, down to the most developed form, where we have a centralized nervous system and conscious sensation, the highest psychic function. We have cellular ideas, histonal ideas, unconscious ideas of the ganglionic cells, conscious ideas in brain cells, all of them being physiological functions of their psychoplasm. Only on the highest stages of animal organism does consciousness develop as a special function of a particular central organ of the nervous system. When the ideas become conscious, and when certain brain centers become highly developed, making possible an extensive association of conscious ideas, the organism becomes fitted to perform the highest functions which we characterize as thinking and deliberation, understanding and reason. We have the same stages in the development of memory and the association of ideas. There are many psychic products of this association of ideas, among them the unity of consciousness. Reason, the instincts, the emotions and the will are explained similarly. All these phases of psychic life are at first unconscious, all are functions of more or less complicated forms of organic matter, and all are subject to physical laws. The great riddle of the origin and nature of the soul is solved by phylogenetic psychology. The human soul is evolved from a long series of other mammalian souls. The historical evolution of the human soul out of a long series of higher and lower mammalian souls must be regarded as a scientifically proved fact.

Consciousness is a natural phenomenon like all the other soul activities. Consciousness is inner intuition, perception, Anschauung, an inner reflection or mirroring. We may divide it into world-consciousness and self-consciousness. The former embraces all possible phenomena of the external world which are possible to our knowledge; the latter is an inner mirroring of our own soul activity, of all ideas, sensations, strivings, and will acts.^[33] Consciousness and psychical life are not identical; psychical life extends farther than consciousness. Unconscious sensations, ideas and impulses also belong to soul life; indeed, this field is larger than the other.

Consciousness is bound to a centralized nervous system. The presence of a nervous central organ, highly developed sense-organs and association-groups, is essential to the existence of unitary consciousness. Protists have no developed ego-consciousness; their sensations and movements are unconscious. In short there is no consciousness until we reach the higher animals. The elementary psychic activities are all unconscious. The riddle of consciousness is no riddle at all. The neurological problem of consciousness is only a special case of the all-embracing cosmological problem, of the problem of substance. The problem of consciousness is a physiological problem, and as such to be reduced to the phenomena of physics and chemistry. Consciousness is therefore only a part of the higher soul activity, and as such dependent upon the normal structure of the corresponding soul organ, the brain. It is absolutely dependent upon the chemical changes of the brain substance. It is not an immaterial being, but a physiological function of the brain. The new-born child is without consciousness; consciousness is a late development, arising first when the child learns to talk.

It is only in the significant moment when the child says I for the first time, when its ego feeling becomes clear, that its self-consciousness begins to sprout, and with this the opposition to the external world.

With the death of man all physiological activities cease, and with them the 'soul,' that is, that sum of brain functions which psychical dualism regards as a separate being, independent of the other manifestations of the living body. The protozoa are just as mortal in the physiological, and hence also in the psychological, sense as the metazoa. Energy and matter are inseparably connected. We distinguish between the psychical energy (sensation, presentation, willing) and psychical matter, by which alone the same can act, that is, the living plasma. The soul is actual; it is the sum of the physiological functions of the material organs. The human soul is a collective term for a sum of brain functions, and these are like all other life processes conditioned by physical and chemical processes, and hence like all the rest subject to the law of substance.

Let us now see what has become of Haeckel's original monistic theory. According to the original proposition there is one underlying substance of which matter and energy are the attributes. What this substance is, no one knows; perhaps it does not exist at all; perhaps it is force; perhaps prothyl, perhaps ether. But never mind that. We have the two aspects of it in extended space-filling stuff, and the sentient energy. All of a sudden this unitary substance begins to turn itself into a plurality of atoms or pyknatoms; the one becomes the many, monism becomes pluralism. How is this to be explained? It is all very simple to Haeckel. Atoms have souls, feelings and desires, and these properties cause the atoms to contract.

Without the assumption of an atom-soul, says Haeckel in another place,^[34] the most common and most general phenomena of chemistry are inexplicable. Pleasure and pain, desire and aversion, attraction and repulsion must belong to all mass-atoms; for the movements of the atoms which must take place in the formation and separation of every chemical combination can be explained only if we ascribe to them sensation and will (Empfindung und Wille).

That is, the physical pluralism is explained by assuming a pluralism of forces. But why the unitary substance should desire to differentiate we are not told. But ignoring this difficulty, we note that these atom-souls or soul-atoms, these properties of sensation and will, cause the atoms to contract, and hence cause motion. That is, the attribute of energy, sentient force, mind, thought, or whatever else Haeckel may choose to call it, causes motion, makes matter move, produces a change in the other attribute. Almost in the same breath we are told that there is no form of energy which is not caused by movements of matter.^[35] That is, the energy causes the movement, and the motion causes the energy. These statements not only contradict each other, but are out of harmony with the original standpoint of Haeckel, according to which mind and matter are attributes of an underlying substance, dependent upon this and not upon each other.

Haeckel's pure monism, we see, seems to turn into the much-despised dualism. But this is only a passing stage in the philosophical drama. We are hurried on rapidly to the denouement in the chapters on the soul, where the so-called psychical processes become the functions of physiological processes, of physical and chemical changes. We have already become acquainted with Haeckel's philosophy of mind; let us here simply accentuate the phases of it which do not agree with the fundamental principles. Soul life is the sum-total of vital phenomena which are all bound to a material substrate, conditioned by physiological functions. Soul is a collective term for the sum-total of the psychic functions of the plasm. 'Soul' is a collective term for a sum of brain functions, which are, like all life-activities, conditioned by physical and chemical processes. Soul life is unconscious until we reach the higher animals where it becomes conscious. Consciousness, however, is merely a development from the lower forms of psychic life and, like these, a function of physiological processes. It is dependent on the chemical changes of the brain; it is a physiological problem and as such solved by physics and chemistry. The sentient energy with which we began, which was at least equal in dignity with matter at the outset, and which assumed importance enough in the scheme to cause the matter to move, to attract and to repel, is now made the function of matter. Matter is the substrate, the substance; soul or mind the function of matter, housed in the latter and dependent upon it. Matter has become king; energy or mind its slave. Our so-called pure monism has changed into materialism, if not in the sense that it reduces everything, energy included, to matter and motion, at least in the sense that it makes this energy an attribute, a function of matter.

Besides the inconsistencies which we have noticed all along the line, there are difficulties in the system upon some of which we have already lightly touched. The continuous substance filling infinite space and endowed with infinite energy must do something if a cosmos is to be formed. It begins to differentiate and to form atoms. We are told why it does so: it has the unconscious impulse to do so, it is endowed with the properties of love and hate, which are only different names for attraction and repulsion. Why the infinite substance should want to do all this, we are left to figure out for ourselves. It is worth noting here, however, that Haeckel introduces the conception of purposive impulse into his explanation of the cosmos, an unconscious impulse or striving, it is true, but still a force attempting to account for the movements of the atoms. He does not therefore repudiate the teleological explanation in toto, as he claims to do, but only conscious teleology.

But in spite of all this the theory does not explain how these animated atoms floating in the ether can produce a world. We have here the same old difficulty which was presented to us by the first Greek atomists. In fact it is somewhat increased. Each pyknatom acts spontaneously; it is not a dead thing buffeted into place by other dead things, but a living thing that seeks its place, that strives to be united with other atoms which also strive, and their harmonious strivings give us a world. This is certainly a mystery of mysteries. Why the little atoms should band themselves together and form molecules, why the molecules should fall into line and form larger bodies of matter, is not explained.

The same difficulty meets us, of course, in the philosophy of organic life. Haeckel supplies us with any number of animated pyknatoms, but we are at a loss what to do with them. How are they to form organisms? Of course, it is just as easy for them to form a simple piece of protoplasm as it is for them to form a planetary system, but there is poor consolation in that when it is a mystery how they can do either. Moreover the mysteries multiply a thousandfold when we pass from the very simplest form to the higher organisms. It is perhaps easy enough to describe what happens, to watch the process of cell division under the microscope, to trace the development through a series of stages, but why should the atoms group themselves in such a way as to form now a polyp, now a man. Each cell has its soul, it is true, unconscious impulse; and combinations of cells have corporate souls in turn, but they sit there helpless, unable to do anything; indeed what can they do, being merely a sum of vital phenomena, a collective term for the sum-total of physiological functions of the psychoplasm? The theory of evolution can not help us here, and the great Darwin frankly confessed that much. It can help us to see that if a certain form is given, that form will tend to survive if it is adapted to its surroundings, but why it should be in the first place, and why it should develop new and more appropriate characteristics in the course of time, it cannot tell us. As has been said by Schurman,^[36] the theory of evolution may explain the survival of the fittest, but it can not explain the arrival of the fittest.

It is strange that Haeckel should have found it necessary to endow his atoms with souls, and then have such a dread of attributing a principle of unity to organic forms. If the atom can have a soul or energy that makes it seek out some atoms and avoid others, why not endow the organism with a soul or force that will do something? I do not mean to advocate the renewal of the doctrine of vitalism in biology, after the fashion of Reinke^[37] and other modern biologists, but I do not see why a man who gives atoms and cells and groups of cells souls, and who uses the atom-souls as a principle of explanation, should draw the line at organic forces or souls. If vitalism and teleology are acceptable in the inorganic world, why should they be so utterly out of the question in the organic realm?

The philosophy of mind is also full of difficulties. The existence of psychical life is not explained, but assumed. The substance is endowed from the beginning with sentient energy, energy that feels pleasure and pain, loves and hates, has desires and aversions, but these states are all unconscious. Unconscious sensations, pleasures, pains and impulses are greater riddles than the things they are manufactured to explain. Haeckel seems to feel this when it comes to organic life, for here he identifies these unconscious processes with physical and chemical forces, though he is vacillating on his point as usual; the physical processes are sometimes the forces themselves, sometimes the functions of these forces. Out of these unconscious processes consciousness arises in the brains of higher animals. The thing is as simple as it can be. Ideas which have been unconscious mirror themselves in the brain, begin to look at themselves. Consciousness develops as a subjective mirroring of the objective processes in the neuroplasm of the soul cells^[38] and the thing is done. What could be fairer than that? And then these mirrored ideas, these ideas or rather brain processes that have suddenly tsken it into their heads to look at themselves, add themselves together and form personalities and all higher processes of mind. The whole problem of existence is a problem of arithmetic. Atoms add themselves together to form bodies, bodies add themselves together to form worlds, ideas add themselves together to form thought, science, philosophy. Instead of answers to problems we get new and more difficult problems. It is no explanation of soul life to assume it as an attribute of the substance; it is no explanation of consciousness to deduce it from unconscious processes; it is no explanation of the human mind to conceive it as a sum-total of ideas.

This gives us Haeckel's philosophy of nature, his philosophy of life and his philosophy of mind. He believes that he has solved for us the problem of the essence of matter and energy, the origin of motion, the origin of life, the purposive arrangement of nature, the origin of thought and language, the origin of simple sensation and consciousness. The problem of matter and energy is solved by making matter and energy attributes of an underlying substance which is a greater riddle than they, and which perhaps does not even exist. We are never told what the essence of any of these things is. Afterwards matter seems to become the substance and energy its function. Energy is conceived as sentient force, as unconscious psychical life, and all the processes of soul life and consciousness are regarded as different forms of it or as functions. of it. Matter, in other words, is the bearer of the different forces of nature, from the forces of attraction and repulsion or unconscious love and hate up to consciousness. Matter is king, energy is the subject. The origin of motion is not explained either. We are told that the substance is in eternal motion: 'motion is as immanent and original a property of the substance as sensation.'^[39] We are also told that force or sentient energy is the cause of motion. If we say motion is original and eternal, we do not explain it, but assume it. If we say it is the effect of force or energy, then we are explaining it by creating a new problem. The origin of life is explained in a general way as the product of inorganic nature; the living plasm originates from inorganic carbon compounds. The physico-chemical properties of carbon are the mechanical causes of the movements of organic bodies. But what are these physical and chemical properties? If they are themselves movements, then we have simply pushed the problem back a station; if they are forces or the so-called sentient energy, then we have avoided vitalism in the organic world by previously introducing it into the inorganic world. As for the problem of the purposeful arrangement of nature, we must agree with Haeckel that the theory of evolution throws a great deal of light upon it, but we can not agree with him that it removes all difficulties and solves all riddles, as we have already pointed out.

In conclusion let us take up Haeckel's ethics and religion. The practical laws, he declares, must be in harmony with a rational Weltanschauung. Our ethical system must therefore be in harmony with the unified conception of the cosmos. The universe forms a single complete whole, the mental and moral life of man forms a part of this cosmos, hence our natural order is a unitary one. We have not two separate worlds, a physical-material world and a moral-immaterial world, but one.

The monistic cosmology has shown that there is no personal God; comparative and genetic psychology has shown that there is no immortal soul; monistic physiology has shown that there is no freedom of the will. The doctrine of evoluton shows that the eternal, necessary laws of nature which govern the inorganic world are valid also for the organic and moral world. This destroys the Kantian dualism in ethics. But there is also a positive side to ethical monism. It shows that the feeling of duty does not rest upon an illusory categorical imperative, but upon the real ground of the social instincts which we find in all higher gregarious animals. It regards as the highest aim of ethics the establishment of a healthy harmony between egoism and altruism. Man has duties towards himself and duties towards others. Both impulses, egoism and altruism, are natural laws which are equally essential to the existence of family and society. Egoism makes possible the self-preservation of the individual, altruism that of the species. The social duties are only higher developments of the social instincts. In civilized man all ethics, theoretical and practical, is connected as a normative science with his philosophy and religion. The golden rule is the fundamental law: Love your neighbor as yourself. Several christian rules of morality contradict this rule: (1) Contempt of self; exaggeration of love of neighbor at expense of self; (2) contempt of body; (3) contempt of nature; (4) contempt of civilization; (5) contempt of family-life; (6) contempt of women.

As to religion Haeckel has this to say. Many scientists regard religion as a thing of the past. They think that the clear insight into the evolution of the world which we have obtained completely satisfies not only the causal need of our reason, but all the highest emotional needs of our nature. This view is in a certain sense true. For a perfectly clear and consistent conception of monism, the notions of religion and science become identical. Only a few decided thinkers reach, however, this view, fewer still have the courage or feel the need of expressing it.

Modern science must not only destroy the illusions of superstition, but erect a new edifice for the human emotions: a place of reason in which we may reverently adore the true trinity of the nineteenth century, the trinity of the true, the beautiful, and the good.

Just as the ancient Greeks embodied their ideals of virtue in the forms of gods, we can give our ideals of reason the forms of goddesses. The Goddess of Truth dwells in the temple of nature, in the green forests, upon the blue seas, on the snow-covered mountain-peaks. The ways of approach to this goddess are loving investigation of nature and its laws, the observation of the infinite world of stars by means of the telescope, and of the infinitely small world of cells by means of the microscope, but not senseless prayers and ceremonies.

Our ideal of virtue largely coincides with the christian ideal, as expressed in the Gospels and Paul's Epistles. The best part of christian morality consists in the rules of humanity, of love and forbearance, of compassion and beneficence. We place as much value, however, upon egoism as upon altruism; perfect virtue consists of a harmony between these.

The extension of our knowledge of nature, the discovery of countless beautiful forms of life, has awakened a new sense of the beautiful in us. Every blade of grass, every bug and butterfly, reveal beauties which we usually pass by. The admiration with which we regard the starry heavens and the microscopic life in a drop of water, the awe with which we examine the wonderful action of energy in the moved matter, the reverence which we feel in the presence of the law of substance,—all these are parts of our emotional life which come under the notion of natural religion.

Our monism also teaches us that we are children of the earth and therefore mortal, that we can enjoy the glories of this planet for a little while.

The modern man who possesses science and art—and hence also religion—needs no special church, no narrow enclosed space in which to worship. For everywhere in open nature, where he turns his eyes upon the infinite universe or upon a part of it, everywhere he finds besides the hard struggle for existence the true, the beautiful and the good everywhere he finds his church in glorious nature herself. Still, it will correspond with the particular needs of many persons to have beautiful temples and churches to which to retire, and these they should have.

We have examined Haeckel's philosophy and have pointed out its inconsistency and inadequateness. It violates the fundamental requirements of scientific hypothesis; it is not consistent with itself, and it does not explain the facts.-It is so full of contradictions that its opponents will have no difficulty in citing passages from the 'World Kiddles' convicting the author of almost any philosophical heresy under the sun, while its defenders will be equally successful in proving by means of other quotations that the charges are unfounded. There is a great deal of truth in what von Hartmann says with respect to Haeckel's philosophy in his 'Geschichte der Metaphysik':

Haeckel is therefore an ontological pluralist, since he conceives nature as a plurality of separate substances (atoms); a metaphysical dualist, since he assumes two metaphysical principles (force and matter) in every single substance; a phenomenal dualist, since he recognizes two different fields of phenomena (external mechanical occurrence and internal sensation and will); a hylozoist, since he ascribes life and soul to every part of matter; a philosopher of identity, since he regards one and the same kind of substances as the ground of both fields of phenomena; a cosmonomic monist, since he denies the teleological uniformity in nature and admits only causal law; and a mechanist, since he regards all causal processes as mechanical processes of material particles.^[40]

The fact is Haeckel's philosophy is no system at all, but a conglomeration of different systems; a metaphysical pot-pourri, a thing of shreds and patches. Perhaps this is one of the reasons of its popularity—Wer vieles bringt wird jedem etwas bringen!

Haeckel's 'World Biddies' proves conclusively that no man can neglect philosophy with impunity, and justifies the existence of a discipline like philosophy. Men will philosophize, even natural scientists—that is plain—and so long as they continue to do that, it is essential that they do it well. And they can not do it well without being trained to the work. It is just as impossible for a man to ignore the history of philosophy and to attempt to originate a system without regard to the race's experiences in system-building stretching over a period of 2,500 years or more, as it is for him to accomplish anything in physics or biology without profiting by the intellectual labors of the past and present in these fields. The man who tries to construct a system of philosophy in absolute independence of the work of his predecessors can not hope to rise very far beyond the crude theories of the beginnings of civilization. Haeckel, of course, is not wholly unaquainted with the history of philosophy, but his utterances usually make the impression on one that he has never done any serious work in this line, that his knowledge is largely based on hearsay, as it were. He certainly seems to be ignorant of modern psychology, otherwise he could not speak of it deprecatingly as he does. His criticisms may perhaps fit the psychology of fifty or a hundred years ago; they surely are not apt to-day. Here Haeckel appears to be fighting windmills of his own making. It is also plain that he is unfamiliar with modern epistemology and that a closer acquaintance with this subject would have saved him from falling into error and contradiction. Haeckel is fond of accusing men like Wundt, Helmholtz, Virchow, Du Bois-Eeymond and others of his age, who started out as materialists and afterwards abandoned the conceptions of their younger days, of cowardice or senility or both. It is barely possible, however, that a deeper insight into the mysteries of nature and a finer appreciation of the inadequacy of the materialistic hypothesis convinced these men of the error of their ways. Haeckel prides himself on having retained the courage of Ms youthful convictions. I think myself that he deserves credit for saying what he really believes, but the fact that he believes what he believes is no sign to me that his friends are in their second childhood, but that Haeckel is still in his first, so far as philosophy is concerned.

1. Lecture delivered at Cornell University under the auspices of the Sage School Philosophical Club.
2. Schmidt, 'Der Kampf um die Weltraethsel' mentions 72 German titles, to which may be added at least two more, making with his own work 75.
3. Loofs, 'Anti-Haeckel.'
4. See particularly 'Die Weltraethsel' pp. 337ff.
5. See also pp. 437f, op. cit., and 'Monismus' p. 40.
6. See also 'Weltraethsel' pp. 19f.
7. See also 'Monismus,' p. 37.
8. See 'Weltraethsel,' p. 141.
9. P. 144.
10. P. 283.
11. See Preface to 'Weltraethsel.'
12. Pp. 260f.
13. 'Monismus,' p. 16.
14. 'Weltraethsel,' p. 97.
15. P. 100. See also pp. 18, 73.
16. See 'Weltraethsel,' pp. 243fF.
17. P. 23.
18. 'Monismus,' p. 13.
19. 'Weltraethsel,' pp. 249f.
20. Weltraethsel,' p. 23. 'Monismus,' p. 27: "For our monism an 'immaterial living spirit' is as unthinkable as a 'dead spiritless matter'; in every atom both are inseparably combined. The other systems conceive force and matter as two essentially different substances."
21. 'Weltraethsel,' pp. 437ff.
22. 'Weltraethsel,' p. 333.
23. 'Weltraethsel,' p. 426.
24. 'Monismus,' pp. 16, 37.
25. 'Weltraethsel,' pp. 250ff.
26. 'Monismus,' p. 14.
27. 'Monismus,' p. 17.
28. 'Weltraethsel,' p. 259. See also 'Monismus' p. 14.
29. 'Weltraethsel,' pp. 206f.
30. 'Weltraethsel,' pp. 296ff.
31. Pp. 101-243.
32. See also 'Monismus,' p. 21.
33. 'Weltraethsel,' pp. 197ff. See also 'Monismus,' pp. 22f.
34. 'Perigenesis der Plastidule,' pp. 38f.
35. 'Weltraethsel,' pp. 255f.
36. 'The Ethical Import of Darwinism.'
37. 'Die Welt als That.'
38. 'Weltraethsel,' p. 151.
39. On page 253 the substance seems to be conceived as originally in a state of rest.
40. Vol. II., p. 456.