It is in the nature of many of our greatest scientific theories that their simplicity and naturalness in the explanation of facts fill us with a sense of wonder that they had not long before suggested themselves to scientists. If, for instance, we were to attempt, in a Cartesian spirit, to free ourselves from all the prejudice of previous dogma and regard only the general course of nature, we could not logically avoid the conclusion, even from a superficial view, that a theory of the gradual development of existing forms has far more probability on its side than that of a creation from without which broke in upon natural process, and placed ready-made suns and planets in the heavens, and finished beasts and men upon the earth. Everywhere in the organic world we behold the process of growth, the development of germs, the passage of the inorganic into the organic, and of the organic into the inorganic again,—change and transformation under natural law.
The difficulty which difference of form and function in the various species offers to a theory of Evolution is by no means so large as has often been claimed; as great difference exists between the oak and the acorn, from which we know it, nevertheless, to spring; as much contrast is exhibited between the brown twigs of the trees and shrubs in winter and the brilliant foliage and flowers which they put forth under the warmer sun of spring; quite as great contrasts may be found, in the life of every human being, between the single cell and the individual completeness attained at birth, between infancy and morally characterized manhood and womanhood, between the vigor of full maturity and the deterioration of age. Even the chasm between the organic and the inorganic is not logically impassable. The necessity of nourishment is the natural bridge between the two, and the equivalence of conditions and result, the indestructibility of matter and motion, establish at once the necessity of the inference that the organic can exist only at the ultimate expense of the inorganic, from which it is continually renewed. Were our senses such that, having before been closed, they were suddenly opened to the perception of the daily observable facts of growth, these would probably appear to us very nearly as strange, anomalous, and impossible as the changes which, according to the Darwinian Theory, have resulted in the existence of different species; and it is obvious that the public mind, becoming gradually accustomed to the conception of the latter changes, does not now regard them as so wonderful and anomalous as they appeared to it in the beginning.
Processes involving complete change of form may be observed, at the present time, everywhere in nature; but they are observable, everywhere in the organic, as growth without breaches; even a primitive science has always recognized the gradual character of motion, the absence of gaps in the causal chain, at least outside of the initiative action of human will. Such a natural hypothesis of creation as we have above supposed, formed upon crude and superficial, but as far as it goes, logical reasoning from facts of observation, could not regard the process as other than a gradual one, in which simpler forms and conditions must be supposed to have preceded more complex ones; in other words, it could not logically conceive the process as other than an evolution.
Traces of an idea of Evolution may be found in various crude forms in nearly all the earlier Greek philosophers, especially in Anaximander, Heraclitus, Democritus, Empedocles, and later in Aristotle. Such traces may even be found in many heathen mythologies in contradistinction from the Judaic. The progress of investigation, establishing the universality of natural law and, in every province, the gradual character of change was, before Darwin, as it has been since his work, in the direction of such a theory, as was shown by the ready acceptance with which Darwinism met, if not by the world at large, at least by the majority of scientists. In England, France, and Germany, there were others at work under the influence of thoughts similar to if not identical with those that inspired the researches and experiments of Darwin; and the nebular theory of Kant had already claimed in Astronomy what the Darwinian claimed in Biology. "When Kant, in his Natural History of the Heavens, which has become the fundament of modern Astronomy, says, 'Give me matter and I will make you a world,' what he intended to express was that the natural laws of matter are perfectly competent to render comprehensible to us the development of our well-known solar system."[94]
In the very beginning, the theory of Evolution may be said to have had three distinct branches, represented by the Nebular Theory in Astronomy, Haeckel's Ontogeny, and the Biology of Lamarck, Darwin, Wallace, and Huxley; and to these should properly be added the Sociological Ethics of Spencer, which was not, however, worked out to a complete system. But Du Prel says of later research: "In the progress of modern science, no principle has proved so fruitful as that of evolution. All branches compete with one another in its use, and have brought about by its aid the most gratifying results. Geology interprets the significance of superimposed, hardened strata of the earth's crust in the sense of a history of the earth's development; Biology, in union with the study of fossils, arranges the living and petrified specimens of plants and animals in their order, and constructs a history of the evolution of organic life; Philology prepares a genealogical tree of languages, and finds in it signs which throw light on prehistoric times, and reveal facts forgotten for thousands of years; Anthropology discovers in the form and expression of human beings rudimentary signs that point to a theory of development from lower forms; and, finally, History reveals the evolution of civilization in far-distant historic times; and in all these branches it becomes apparent that we only then understand phenomena when we have comprehended their Becoming."[95]
It is due to the gradual perception of the fact that some such theory as that of Evolution is implied in the very conception of the constancy of nature that there has been a continual decrease of that negative form of criticism which has made much of the gaps in the direct proof. Modern science has so grown to, and by, the theory of Evolution that the overthrow of the latter means nothing more nor less than the destruction of science itself in its highest results. Even those who reject the conclusions of Evolution are found to make use of its methods, and must do so perforce. As the breadth and depth and height of the theory come to be perceived, it is seen that the demand for complete proof is nothing more nor less than a demand for the perfection of all branches of knowledge, the refusal of credit without such proof a refusal to place any confidence in the first principles of scientific theory until it has fully explored the universe and left nothing further to be discovered. But science would have less ground for complaint, if the opponents of Darwinism consistently refused, on the ground of the incompleteness of our knowledge, to form any theory whatever on the subject of man's nature and development, permitting the worth of the evolutional theory to be determined by its future results in application as hypothesis. But the peculiar spectacle is afforded us of a party rejecting a theory supported by numberless facts in all branches, and whose very breaches the direction of discovery continually tends to bridge, in favor of a dogma which cannot point to one scientific fact in its support,—a party demanding absolute perfection of proof as the condition of its acceptance of one theory, while it at the same time fiercely defends a conception of nature of which it cannot furnish the most imperfect proof. It is true that mankind has not beheld the evolution of the whole vegetable and animal kingdom. But neither had any human eye ever yet beheld the planet Neptune when Le Verrier prophesied its existence and calculated its size and position. The theory of Evolution is a reasoning from the constancy of nature, as was that of Le Verrier, only, in the case of the former, we have the observation and calculations of not one scientist alone, but of thousands, on which to rely. To demand of the scientist that he shall produce the organic from the inorganic, and practically demonstrate the change of form and function, and the process of separation of species, before the possibility of such development is conceded, is on a par with demanding of him an actual reproduction of the Glacial Period before the theory of its previous existence shall be accepted. There is no reason for supposing that, if spontaneous generation once took place, the peculiar complication of conditions which produced it will ever again recur or can be artificially constructed.
But science has no desire to be dogmatic. It readily acknowledges the total absence of direct and established proof at this particular juncture of the beginning of life. It can only point to the indirect testimony of Physiological Chemistry and Crystallogeny, to the simplicity of structure and movement in certain forms of life, and finally to the observed constancy of nature. But an exaggerated significance has been given to this chief flaw in the theory of Evolution, by those who, starting with the intention of defending Theology or the dignity of the Human, have been driven back, step by step, to this point, and fail to perceive that, arrived here, they have already abandoned the ground on which contest was possible. What significance a primal creation merely of lowest organisms can have, for either a defence of human dignity or for Christian Theology, it is difficult to perceive. As a matter of choice, it would seem to be more consistent with the omnipotence and dignity of a Creator to suppose that these very simple organisms arose, like other forms, under the action of natural law than that special interference was necessary in just their case. But, supposing such a special Creation, the following questions immediately present themselves from the theological standpoint: Are these special creations endowed with soul? If so, they must be immortal; if not, then soul arises in the process of evolution; if it arises as do all other things, qualities, functions, by growth,—that is, by the addition of infinitesimal increments (as we must, indeed, suppose it to arise if we regard it as "evolved")—then whence come these increments? If they come direct from a Creator, then surely no special favor towards man in the bestowment of soul can be alleged; and if they arise by natural causes, out of nature, then why may not their first beginning, their first infinitesimal appearance, also be supposed to be due to such causes?
The proof of an increase, a growth, of what have been called distinctively the mental faculties, throughout the animal kingdom, is every day stronger. No one believes, at the present date, with Descartes, that the animals are automata. Differences of mental power would seem to be but differences of degree; the facts all point to such a theory. The more scientific theologians have, indeed, abandoned this with the other minor points of contest above discussed, and devoted their efforts to argument from the moral nature of man. Philology, Anthropology, and Geology testify to mental progress, even in the human species; and if such a progress is a fact, it cannot have been without influence upon the moral nature of man, even supposing the latter to be God-given. Indeed, a merely physical progress or change cannot have been without such influence; for the most conservative theologians admit the strong action of the body upon the mind. It would seem, then, for all reasons, that an investigation of the process of mental evolution, or of evolution in general, ought not to be without results significant for any system of morality. If it is true that we learn wisdom and morality from human history, this can be so only because history gives us increased knowledge of the constancy of nature in those of its manifestations which specially concern the human, and thus enables us better to judge the present and predict the future. We should suppose that a still wider knowledge of our mental and physical evolution must be of yet greater worth to us in the same manner,—that the disclosure of more extended fields of nature to our vision must afford us new and valuable lessons with regard to ourselves; just as the telescope makes no discovery in the most distant regions of space that does not prove to have, in the end, its peculiar significance for our own planet. If our investigations should prove fruitless, as all such investigations have been said by some to be, the fact, established a posteriori, could not be disputed. But, considering all the points above noticed, such a result could not but astonish us; and we should even be inclined, after all that has been said, to suspect that the fault lay rather in the particular method than in the direction of our research.
FOOTNOTES:
[87] "Natürliche Schöpfungsgeschichte," 8th ed., p. 109.