It should be noted, too, that while to us who come after, the great complex evolutionary movement of the two last centuries justly reveals itself as one and indivisible, a single grand cosmical drama, having many acts and many scenes, but all alike inspired by one informing and pervading unity, yet to those whose half unconscious co-operation slowly built it up by episodes, piecemeal, each act and each scene unrolled itself separately as an end in itself, to be then and there attained and proved, quite apart from the conception of its analytic value as a part in a great harmonious natural poem of the constitution of things. Though evolution appears to us now as a single grand continuous process, a phase of the universe dependent upon a preponderating aggregation of matter and dissipation of energy, yet to Kant and Laplace it was the astronomical aspect alone that proved attractive, to Darwin it was the biological aspect alone, and to many of the modern workers in the minor fields it is the human and sociological aspect that almost monopolises the whole wide mental horizon. No greater proof can be given of the subjective distinctness of parts in what was objectively and fundamentally a single broad psychological revolution of the human mind, than the fact that Lyell himself, who more than any one man had introduced the evolutionary conception into the treatment of geology, should have stood out so long and fought so blindly against the evolutionary conception in the organic world. Indeed, it was not until the various scattered and many-coloured strands of evolutionary thought had been gathered together and woven into one by the vast catholic and synthetic intelligence of Herbert Spencer that the idea of evolution as a whole, as a single continuous cosmical process, began to be apprehended and gradually assimilated by the picked intelligences of the several distinct scientific departments.
Observe also that the evolutionary method has invaded each of the concrete sciences in the exact order of their natural place in the hierarchy of knowledge. It had been applied to astronomy by Kant and Laplace before it was applied to geology by Lyell; it had been applied to geology by Lyell before it was applied to biology by Darwin; it had been applied to biology (in part, at least) by Lamarck and the Darwins before it was applied to psychology by Spencer; and it is only at the very end of all that it has been applied to sociology and the allied branches of thought by a hundred different earnest workers in contemporary Europe. Each stage helped on the next; each was dependent only on those that went naturally before it, and aided in turn the subsequent development of those that naturally came after it.
Nevertheless, the popular instinct which regards Darwinism and evolution as practically synonymous is to a large extent justified by the actual facts of the psychological upheaval. Darwin's work forms on the whole the central keystone of the evolutionary system, and deserves the honour which has been thrust upon it of supporting by its own mass the entire superstructure of the development theory.
For, in the first place, Darwin had to deal with the science of life, the science where the opposition to evolutionism was sure to be strongest, and where the forces and tendencies in favour of obscurantism were sure to gather in fullest force. Every other great onward step in our knowledge of our own relation to the universe of which we form a part had been compelled indeed to run the gauntlet, in its own time, of ecclesiastical censure and of popular dislike. Those inveterate prejudices of human ignorance which sedulously hide their genuine shape under the guise of dogma masquerading as religion, had long since brought to bear their baneful resources upon the discoveries of Copernicus and the theories of Galileo, as blind, misleading, and diabolical lights, opposed to the sure and certain warranty of Holy Scripture. Newton, again, had in due time been blamed in that he boldly substituted (as his critics declared) the bald and barren formula of gravitation for the personal superintendence of a divine Providence. Laplace had been accused of dethroning the deity from the centre and governance of his celestial system. Around the early geologists the battle of the six days of creation had raged fiercely for nearly half a century. But all these varying modes of thought, though deemed heretical enough in their own day, had touched, as it were, but the minor ramparts and unimportant out-works of the great obscurantist dogmatic strongholds: Darwinism, by openly attacking the inmost problems of life and mind, had brought to bear its powerful artillery upon the very keep and highest tower of the fortress itself. The belief that the various stars, planets, and satellites had or had not been wisely created in their existing positions, and with their present orbits, movements, and relations accurately fore-measured, did not fundamentally affect, for good or evil, the cherished dogmas of the ordinary multitude. But the analogous belief in the distinct and separate creation of plants and animals, and more especially of the human species, was far more closely and intimately bound up with all the current religious conceptions. It was at first supposed, not perhaps without some practical wisdom, that to upset the primitive faith in the separate creation of living beings was to loosen and imperil the very foundations of common morality and revealed religion. The 'argument from design' had been immemorially regarded as the principal buttress of orthodox thought. Theologians had unwisely staked their all upon the teleological dogma, and could ill afford to retire without a blow from that tenaciously defended bastion of their main position. Hence the evolutionary concept had its hardest fight to wage over the biological field; and when that field was once fairly won, it had little more to fear from banded preconceptions and established prejudices in any other portion of the wide territory it claimed for its own.
In the second place, biological evolution, firmly established by Darwin on a safe, certain, and unimpeachable basis, led naturally and almost inevitably to all the other innumerable applications of the evolutionary method, in the domains of psychology, sociology, philology, political thought, and ethical science. Hence the immediate and visible results of its promulgation have been far more striking, noticeable, and evident than those which followed the establishment of the evolutionary conception in the astronomical and geological departments. It was possible to accept cosmical evolution and solar evolution and planetary evolution, without at the same time accepting evolution in the restricted field of life and mind. But it was impossible to accept evolution in biology without at the same time extending its application to psychology, to the social organism, to language, to ethics, to all the thousand and one varied interests of human life and human development. Now, most people are little moved by speculations and hypotheses as to the origin of the milky way or the belt of Orion; they care very slightly for Jupiter's moons or Saturn's rings; they are stolidly incurious as to the development of the earth's crust, or the precise date of the cretaceous epoch; but they understand and begin to be touched the moment you come to the practical questions of man's origin, nature, and history. Darwinism compelled their attention by its immediate connection with their own race; and the proof of this truth is amply shown by the mere fact that out of all the immense variety of Charles Darwin's theories and ideas, the solitary one which alone has succeeded in attaching to itself the public interest and public ridicule is the theory of man's ultimate descent from a monkey-like ancestor. Popular instinct, here as elsewhere profoundly true at core in the midst of all its superficial foolishness, has rightly hit upon the central element in the Darwinian conception which more than any other has caused its fruitful and wonderful expansion through every fertile field of human enquiry.
In short, it was Darwin's task in life to draw down evolution from heaven to earth, and to bring within the scope of its luminous method all that is most interesting to the uninstructed and unsophisticated heart of the natural man.
The application of the evolutionary principle to the world of life, human or animal, thus presents itself as the chief philosophic and scientific achievement of the nineteenth century. Throughout the whole middle decades of the present age, the human mind in all its highest embodiments was eagerly searching, groping, and enquiring after a naturalistic explanation of the origin and progress of organic life. In the vast scheme for the System of Synthetic Philosophy which Herbert Spencer set forth as an anticipatory synopsis of his projected work, the philosopher of development leapt at once from the First Principles of evolution as a whole to the Principles of Biology, Psychology, and Sociology, omitting all reference to the application of evolution to the vast field of inorganic nature; and he did so on the distinctly stated ground that its application to organic nature was then and there more important and interesting. That suggestive expression of belief aptly sums up the general attitude of scientific and philosophic minds at the precise moment of the advent of Darwinism. Kant and Laplace and Lyell had already applied the evolutionary method to suns and systems, to planets and continents; what was needed next was that some deeply learned and universally equipped biological leader should help the lame evolutionism of Lamarck over the organic stile, and leave it free to roam the boundless fields of what Mr. Spencer has sometimes well described as the super-organic sciences. For that office, Darwin at the exact moment presented himself; and his victory and its results rightly entitle him to the popular regard as the founder of all that most men mean when they speak together in everyday conversation of the doctrine of evolution.
On the other hand, the total esoteric philosophic conception of evolution as a cosmical process, one and continuous from nebula to man, from star to soul, from atom to society, we owe rather to the other great prophet of the evolutionary creed, Herbert Spencer, whose name will ever be equally remembered side by side with his mighty peer's, in a place of high collateral glory. It is he who has given us the general definition of evolution as a progress from an indefinite, incoherent homogeneity to a definite coherent heterogeneity, accompanying an integration of matter and dissipation of motion, or, as we should now perhaps more correctly say, of energy. In the establishment of the various lines of thought which merge at last in that magnificent cosmical law, it was Darwin's special task to bring the phenomena of organic life well within the clear ken of known and invariable natural processes.