In the earlier history of modern natural science, the tendency was to take nature as we find it, without speculation as to the origin of living things, which men were content to regard as direct products of creative power. But at a very early period—and especially after the revelations of geology had disclosed a succession of ascending dynasties of life—such speculations, which, independently of science, had commended themselves to the poetical and philosophical minds of antiquity, were revived. In France more particularly, the theories of Buffon, Lamarck, and Geoffroy St. Hilaire opened up these exciting themes, and they might even then have attained to the importance they have since acquired but for the great and judicial intellect of Cuvier, which perceived their futility and guided the researches of naturalists into other and more profitable fields. The next stimulus to such hypotheses was given by the progress of physiology, and especially by researches into the embryonic development of animals and plants. Here it was seen that there are homologies and likenesses of plan linking organisms with each other, and that in the course of their development the more complex creatures pass through stages corresponding to the adult condition of lower forms. The questions raised by the geographical distribution of animals, as ascertained by the numerous expeditions and scientific travellers of modern times, tended in the same direction. The way was thus prepared for the broad generalizations of Darwin, who, seizing on the idea of artificial selection as practised by breeders of animals and plants, and imagining that something similar takes place in the natural struggle for existence, saw in this a plausible solution for the question of the progress and the variety of organized beings.
The original Darwinian theory was soon found to be altogether insufficient to account for the observed facts, because of the tendency of the bare struggle for existence to produce degradation rather than elevation; because of the testimony of geology to the fact that introduction of new species takes place in times of expansion rather than of struggle; because of the manifest tendency of the breeds produced by artificial selection to become infertile and die out in proportion to their deviation from the original types; and because of the difficulty of preventing such breeds from reverting to the original forms, which seem in all cases to be perfectly equilibrated in their own parts and adapted to external nature, so that varieties tend, as if by gravitative law, to fall back into the original moulds. A great variety of other considerations—as those of sexual selection, reproductive acceleration and retardation, periods of more and less rapid evolution, innate tendency to vary at particular times and in particular circumstances—have been imported into the original doctrine. Thus the original Darwinism is a thing of the past, even in the mind of its great author, though it has proved the fruitful parent of a manifold progeny of allied ideas which continue to bear its name. In this respect Darwinism is itself amenable to the law of evolution, and has been continually changing its form under the influence of the controversial struggles which have risen around it.
Darwinism was not necessarily atheistic or agnostic. Its author was content to assume a few living beings or independent forms to begin with, and did not propose to obtain them by any spontaneous action of dead matter, nor to account for the primary origin of life, still less of all material things. In this he was sufficiently humble and honest; but the logical weakness of his position was at once apparent. If creation was needed to give a few initial types, it might have produced others also. The followers of Darwin, therefore, more especially in Germany, at once pushed the doctrine back into Agnosticism and Monism, giving to it a greater logical consistency, but bringing it into violent conflict with theism and with common sense.
Darwin himself early perceived that his doctrine, if true, must apply to man—in so far, at least, as his bodily frame is concerned. Man is in this an animal, and closely related to other animals. To have claimed for him a distinct origin would have altogether discredited the theory, though it might be admitted that, man having appeared, his free volition and his moral and social instincts would at once profoundly modify the course of the evolution. On the other hand, the gulf which separates the reason and the conscience of man from instinct and the animal intelligence of lower creatures opposed an almost impassable barrier to the union of man with lower animals; and the attempt to bridge this gulf threatened to bring the theory into a deadly struggle with the moral, social, and religious instincts of mankind. In face of this difficulty, Darwin and most of his followers adopted the more daring course of maintaining the evolution of the whole man from lower forms, and thereby entered into a warfare, which still rages, with psychology, ethics, philology, and theology.
It is easy for shallow evolutionists unaware of the tendencies of their doctrine, or for latitudinarian churchmen careless as to the maintenance of truth if only outward forms are preserved and comprehension secured, to overlook or make light of these antagonisms, but science and common sense alike demand a severe adherence to truth. It becomes, therefore, very important to ascertain to what extent we are justified in adopting the agnostic evolution in its relation to life and man on scientific grounds. Perhaps this may best be done by reviewing the argument of Haeckel in his work on the evolution of man—one of the ablest, and at the same time most thorough, expositions of monistic evolution as applied to lower animals and to men.
Ernst Haeckel is an eminent comparative anatomist and physiologist, who has earned a wide and deserved reputation by his able and laborious studies of the calcareous sponges, the radiolarians, and other low forms of life. In his work on The Evolution of Man he applies this knowledge to the solution of the problem of the origin of humanity, and sets himself not only to illustrate, but to "prove," the descent of our species from the simplest animal types, and even to overwhelm with scorn every other explanation of the appearance of man except that of spontaneous evolution. He is not merely an evolutionist, but what he terms a "monist," and the monistic philosophy, as defined by him, includes certain negations and certain positive principles of a most comprehensive and important character. It implies the denial of all spiritual or immaterial existence. Man is to the monist merely a physiological machine, and nature is only a greater self-existing and spontaneously-moving aggregate of forces. Monism can thus altogether dispense with a Creative Will as originating nature, and adopts the other alternative of self-existence or causelessness for the universe and all its phenomena. Again, the monistic doctrine necessarily implies that man, the animal, the plant, and the mineral are only successive stages of the evolution of the same primordial matter, constituting thus a connected chain of being, all the parts of which sprang spontaneously from each other. Lastly, as the admixture of primitive matter and force would itself be a sort of dualism, Haeckel regards these as ultimately one, and apparently resolves the origin of the universe into the operation of a self-existing energy having in itself the potency of all things. After all, this may be said to be an approximation to the idea of a Creator, but not a living and willing Creator. Monism is thus not identical with pantheism, but is rather a sort of atheistic monotheism, if such a thing is imaginable; and vindicates the assertion attributed to a late lamented physical philosopher—that he had found no atheistic philosophy which had not a God somewhere.
Haeckel's own statement of this aspect of his philosophy is somewhat interesting. He says: "The opponents of the doctrine of evolution are very fond of branding the monistic philosophy grounded upon it as 'materialism' by comparing philosophical materialism with the wholly different and censurable moral materialism. Strictly, however, our 'monism' might as accurately or as inaccurately be called spiritualism as materialism. The real materialistic philosophy asserts that the phenomena of vital motion, like all other phenomena of motion, are effects or products of matter. The other opposite extreme, spiritualistic philosophy, asserts, on the contrary, that matter is the product of motive force, and that all material forms are produced by free forces entirely independent of the matter itself. Thus, according to the materialistic conception of the universe, matter precedes motion or active force; according to the spiritualistic conception of the universe, on the contrary, active force or motion precedes matter. Both views are dualistic, and we hold them both to be equally false. A contrast to both is presented in the monistic philosophy, which can as little believe in force without matter as in matter without force."
It is evident that if Haeckel limits himself and his opponents to matter and force as the sole possible explanations of the universe, he may truly say that matter is inconceivable without force and force inconceivable without matter. But the question arises, What is the monistic power beyond these—the "power behind nature"? and as to the true nature of this the Jena philosopher gives us only vague generalities, though it is quite plain that he cannot admit a Spiritual Creator. Further, as to the absence of any spiritual element from the nature of man, he does not leave us in doubt as to what he means; for immediately after the above paragraph he informs us that "the 'spirit' and the 'mind' of man are but forces which are inseparably connected with the material substance of our bodies. Just as the motive-power of our flesh is involved in the muscular form-element, so is the thinking force of our spirit involved in the form-element of the brain." In a note appended to the passage, he says that monism "conceives nature as one whole, and nowhere recognizes any but mechanical causes." These assumptions as to man and nature pervade the whole book, and of course greatly simplify the task of the writer, as he does not require to account for the primary origin of nature, or for anything in man except his physical frame; and even this he can regard as a thing altogether mechanical.
It is plain that we might here enter our dissent from Haeckel's method, for he requires us, before we can proceed a single step in the evolution of man, to assume many things which he cannot prove. What evidence is there, for example, of the possibility of the development of the rational and moral nature of man from the intelligence and the instinct of the lower animals, or of the necessary dependence of the phenomena of mind on the structure of brain-cells? The evidence, so far as it goes, seems to tend the other way. What proof is there of the spontaneous evolution of living forms from inorganic matter? Experiment so far negatives the possibility of this. Even if we give Haeckel, to begin with, a single living cell or granule of protoplasm, we know that this protoplasm must have been produced by the agency of a living vegetable cell previously existing; and we have no proof that it can be produced in any other way. Again, what particle of evidence have we that the atoms or the energy of an incandescent fire-mist have in them anything of the power or potency of life? We must grant the monist all these postulates as pure matters of faith, before he can begin his demonstration; and, as none of them are axiomatic truths, it is evident that so far he is simply a believer in the dogmas of a philosophic creed, and in this respect weak as other men whom he affects to despise.
We may here place over against his authority that of another eminent physiologist, of more philosophic mind, Dr. Carpenter, who has recently said: "As a physiologist I must fully recognize the fact that the physical force exerted by the body of man is not generated de novo by his will, but is derived directly from the oxidation of the constituents of his food. But, holding it as equally certain—because the fact is capable of verification by every one as often as he chooses to make the experiment—that in the performance of every volitional movement physical force is put in action, directed, and controlled by the individual personality or ego, I deem it as absurd and illogical to affirm that there is no place for a God in nature, originating, directing, and controlling its forces by his will, as it would be to assert that there is no place in man's body for his conscious mind."