To most people Darwinism and evolution mean one and the same thing. After what has here been said, however, with regard to the pre-Darwinian evolutionary movement, and the distinction between the doctrines of descent with modification and of natural selection, it need hardly be added that the two are quite separate and separable in thought, even within the limits of the purely restricted biological order. Darwinism is only a part of organic evolution; the theory, as a whole, owes much to Darwin, but it does not owe everything to him alone. There were biological evolutionists before ever he published the 'Origin of Species;' there are biological evolutionists even now who refuse to accept the truth of his great discovery, and who cling firmly to the primitive faith set forth in earlier and cruder shapes by Erasmus Darwin, by Lamarck, or by Robert Chambers.
Much more, then, must Darwinism and the entire theory of organic development to which it belongs be carefully discriminated, as a part or factor, from evolution at large, as a universal and all-embracing cosmical system. That system itself has gradually emerged as a slow growth of the past two centuries, a progressive development of the collective scientific and philosophical mind of humanity, not due in its totality to any one single commanding thinker, but summing itself up at last in our own time more fully in the person and teaching of Mr. Herbert Spencer than of any other solitary mouthpiece. Indeed, intimately as we all now associate the name of Darwin with the word 'evolution,' that term itself (whose vogue is almost entirely due to Mr. Spencer's influence) was one but rarely found upon Darwin's own lips, and but rarely written by his own pen. He speaks rather of development and of natural selection than of evolution: his own concern was more with its special aspect as biological modification than with its general aspect as cosmical unfolding. Let us ask, then, from this wider standpoint of a great and far-reaching mental revolution, what was Charles Darwin's exact niche in the evolutionary movement of the two last centuries?
Evolutionism, as now commonly understood, may be fairly regarded as a mode of envisaging to ourselves the history of the universe, a tendency or frame of mind, a temperament, one might almost say, or habit of thought rather than a definite creed or body of dogmas. The evolutionist looks out upon the cosmos as a continuous process unfolding itself in regular order in obedience to definite natural laws. He sees in it all, not a warring chaos restrained by the constant interference from without of a wise and beneficent external power, but a vast aggregate of original elements, perpetually working out their own fresh redistribution, in accordance with their own inherent energies. He regards the cosmos as an almost infinite collection of material atoms, animated by an almost infinite sum-total of energy, potential or kinetic.
In the very beginning, so far as the mental vision of the astronomer can dimly pierce with hypothetical glance the abyss of ages, the matter which now composes the material universe seems to have existed in a highly diffuse and nebulous condition. The gravitative force, however, with which every atom of the whole vast mass was primarily endowed, caused it gradually to aggregate around certain fixed and definite centres, which became in time the rallying-points or nuclei of future suns. The primitive potential energy of separation in the atoms of the mass was changed into actual energy of motion as they drew closer and closer together about the common centre, and into molecular energy or heat as they clashed with one another in bodily impact around the hardening core. Thus arose stars and suns, composed of fiery atomic clouds in a constant state of progressive concentration, ever gathering-in the hem of their outer robes on the surface of the solid globe within, and ever radiating off their store of associated energy to the impalpable and hypothetical surrounding ether. This, in necessarily brief and shadowy abstract, is the nebular theory of Kant and Laplace, as amended and supplemented by the modern doctrine of the correlation and conservation of energies.
Applied to the solar system, of which our own planet forms a component member, the evolutionary doctrine (in its elder shape) teaches us to envisage that minor group as the final result of a single great diffuse nebula, which once spread its faint and cloud-like mass with inconceivable tenuity, at least as far from its centre, now occupied by the sun's body, as the furthest point in the orbit of Neptune, the outermost of the yet known planets. From this remote and immense periphery it has gradually gathered itself in, growing denser and denser all the time, towards its common core, and has left behind, at irregular intervals, concentric rings or belts of nebulous matter, which, after rupturing at their weakest point, have hardened and concentrated round their own centre of gravity into Jupiter, Saturn, the Earth, or Venus. The main central body of all, retreating ever within as it dropped in its course the raw material of the planetary masses, has formed, at last, the sun, the great ruler and luminary of our system. Much as this primitive evolutionary concept of the development and history of the solar system has been modified and altered of late years by recent researches into the nature of comets and meteors and of the sun's surface, it still remains for all practical purposes of popular exposition the best and simplest mental picture of the general type of astronomical evolution. For the essential point which it impresses upon the mind is the idea of the planets in their several orbits and with their attendant satellites as due, not to external design and special creation, in the exact order in which we now see them, but to the slow and regular working out of preordained physical laws, in accordance with which they have each naturally assumed, by pure force of circumstances, their existing size, and weight, and orbit, and position.
Geology has applied a similar conception to the origin and becoming of the earth's material and external features as we now know them. Accepting from astronomy the notion of our planet's primary condition as a cooling sphere of incandescent matter, it goes on to show how the two great envelopes, atmospheric and oceanic, gaseous and liquid, have gradually formed around its solid core; how the hard crust of the central mass has been wrinkled and corrugated into mountain chain and deep-cut valley, uplifted here into elevated table-land or there depressed into hollow ocean bed; how sediment has slowly gathered on the floor of the sea, and how volcanic energies or lateral pressure have subsequently forced up the resulting deposits into Alpine peaks and massive continents. In this direction, it was Lyell who principally introduced into science the uniformitarian or evolutionary principle, who substituted for the frequent cataclysms and fresh beginnings of the earlier geologists the grand conception of continuous action, producing from comparatively infinitesimal but cumulative causes effects which at last attain by accretion the most colossal proportions.
Here biology next steps in, with its splendid explanation of organic life, as due essentially to the secondary action of radiated solar energy on the outer crust of such a cooling and evolving planet. Falling on the cells of the simplest green plants, the potent sunlight dissociates the carbon from the oxygen in the carbonic acid floating in the atmosphere, and builds it up with the hydrogen of water in the tissues of the organism into starches and other organic products, which differ from the inert substances around them, mainly by the possession of locked-up solar energy. On the energy-yielding food-stuffs thus stored up the animal in turn feeds and battens, reducing what was before potential into actual motion, just as the steam-engine reduces the latent solar energy of coal into visible heat and visible movement in its furnace and its machinery. How the first organism came to exist biology has not yet been able fully to explain for us; but aided by chemical science it has been able to show us in part how some of the simpler organic bodies may have been originally built up, and it does not despair of showing us in the end how the earliest organism may actually have been produced from the prime elements of oxygen, hydrogen, nitrogen, and carbon. Into this most fundamental of biological problems, however, Darwin himself, with his constitutional caution and dread of speculative theorising, was not careful or curious to enter. Even upon the far less abstruse and hypothetical question, whether all life took its prime origin from a single starting-point or from several distinct and separate tribal ancestors, he hardly cared so much as to hazard a passing speculation. With splendid self-restraint he confined his attention almost entirely to the more manageable and practical problem of the origin of species by natural selection, which lay then and there open for solution before him. Taking for granted the existence of the original organism or group of organisms, the fact of reproduction, and the tendency of such reproduction to beget increase in a geometrical ratio, he deduced from these elementary given factors the necessary corollary of survival of the fittest, with all its marvellous and far-reaching implications of adaptation to the environment and specific distinctions. By doing so, he rendered conceivable the mechanism of evolution in the organic world, thus bringing another great aspect of external nature within the range of the developmental as opposed to the miraculous philosophy of the cosmos.
Psychology, once more, in the hands of Herbert Spencer and his followers, not wholly unaided by Darwin himself, has extended the self-same evolutionary treatment to the involved and elusive phenomena of mind, and has shown how from the simplest unorganised elements of feeling, the various mental powers and faculties as we now know them, both on the intellectual and on the emotional side, have been slowly built up in the long and ever-varying interaction between the sentient organism and the natural environment. It has traced the first faint inception of a nervous system as a mere customary channel of communication between part and part; the gradual growth of fibre and ganglion; the vague beginnings of external sense-organ and internal brain; the final perfection of eye and ear, of sight and hearing, of pleasure and pain, of intellect and volition. It has thus done for the subjective or mental half of our complex nature what biology, as conceived by Darwin, has done for the physical or purely organic half; it has traced the origin and development of mind, without a single break, from its first faint and half-unconscious manifestation in the polyp or the jelly-fish to its final grand and varied outcome in the soul of the poet or the intellect of the philosopher.
Finally, sociology has applied the evolutionary method to the origin and rise of human societies, with their languages, customs, arts, and institutions, their governmental organisation and their ecclesiastical polity. Taking from biology the evolving savage, viewed as a developed and highly gifted product of the anthropoid stock, it has shown by what stages and through what causes he has slowly aggregated into tribes and nations; has built up his communal, polygamic, or monogamic family; has learnt the use of fire, of implements, of pottery, of metals; has developed the whole resources of oral speech and significant gesture; has invented writing, pictorial or alphabetic; has grown up to science, to philosophy, to morals, and to religion. The chief honours of this particular line of enquiry, the latest and youngest of all to receive the impact of the evolutionary impulse, belong mainly to Tylor, Lubbock, and Spencer in England, and to Haeckel, De Mortillet, and Wagner on the continent.
In the sublime conception of the external universe and its present workings which we thus owe to the independent efforts of so many great progressive thinkers, and which has here been briefly and inadequately sketched out, Darwin's work in life falls naturally into its own place as the principal contribution to the evolutionary movement in the special biological department of thought. Within the more limited range of that department itself, the evolutionary impulse did not owe its origin to Charles Darwin personally; it took its rise with Erasmus Darwin, Buffon, and Lamarck, and it derived from our great modern English naturalist its final explanation and definitive proof alone. But just as the evolutionary movement in astronomy and cosmical thought is rightly associated in all our minds with the mighty theories of Kant, Laplace, and Herschel; just as the evolutionary movement in geology is rightly associated with the far lesser yet brilliant and effective personality of Lyell; just as the evolutionary movement in the derivative sciences is rightly associated with so many great still living thinkers; so the evolutionary movement in biology in particular rightly sums itself up in the honoured name of Charles Darwin. For what others suspected, he was the first to prove; where others speculated, he was the first to observe, to experiment, to demonstrate, and to convince.
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.