Moreover, fortunately for the world, Darwin's own mind was essentially one of the inductive type. If a great deductive thinker and speculator like Herbert Spencer had hit upon the self-same idea of survival of the fittest, he might have communicated it to a small following of receptive disciples, who would have understood it and accepted it, on a priori grounds alone, and gradually passed it on to the grades beneath them; but he would never have touched the slow and cautious elephantine intellect of the masses. The common run of mankind are not deductive; they require to have everything made quite clear to them by example and instance. The English intelligence in particular shows itself as a rule congenitally incapable of appreciating the superior logical certitude of the deductive method. Englishmen will not even believe that the square on the hypotenuse is equal to the squares on the containing sides until they have measured and weighed as well as they are able by rude experimental devices a few selected pieces of rudely shaped rectangular paper. It was a great gain, therefore, that the task of reconstructing the course of organic evolution should fall to the lot of a highly trained and masterly intelligence of the inductive order. Darwin had first to convince himself, and then he could proceed to convince the world. He set about the task with characteristic patience and thoroughness. No man that ever lived possessed in a more remarkable degree than he did the innate capacity for taking trouble. For five years, as a mere preliminary, he accumulated facts in immense variety, and then for the first time and in the vaguest possible way he—'allowed himself to speculate.' That brings us down to the year 1842, when the first notes of the 'Origin of Species' must have been tentatively committed to paper. It was in 1859 that the first edition of the complete work was given to the world. Compare this with the case of Newton, who similarly kept his grand idea of gravitation for many years in embryo, until more exact measurements of the moon's mass and distance should enable him to verify it to his own satisfaction.
One other item of immense importance in the genesis of the full Darwinian doctrine deserves mention here—I mean, the exact moment of time occupied by Charles Darwin in the continuous history of scientific thought. A generation or two earlier, in Erasmus Darwin's days, biology had not yet arrived at the true classification of animals and plants upon an essentially hereditary basis. The Linnæan arrangement, then universally accepted, was wholly artificial in its main features; it distributed species without regard to their fundamental likenesses of structure and organisation. But the natural system of Jussieu and De Candolle, by arranging plants into truly related groups, made possible the proofs of an order of affiliation in the vegetable kingdom; while Cuvier's similar reconstruction of the animal world gave a like foothold to the evolutionary philosopher in the other great department of organic nature. The recognition of kinship between the various members of the same family necessarily preceded the establishment of a regular genealogical theory of life in its entirety.
Though we are here concerned mainly with Charles Darwin the thinker and writer—not with Charles Darwin the husband and father—a few words of explanation as to his private life must necessarily be added at the present point, before we pass on to consider the long, slow, and cautious brewing of that wonderful work, the 'Origin of Species,' Darwin returned home from the voyage of the 'Beagle' at the end of the year 1836. Soon after, he was elected a Fellow of the Royal Society, no doubt through the influence of his friend Lyell, who was quite enthusiastic over his splendid geological investigations on the rate of elevation in the Pampas and the Cordillera. Acting on Lyell's advice, too, he determined to seek no official appointment, but to devote himself entirely for the rest of his life to the pursuit of science. In 1838, at the age of twenty-nine, he read before the Geological Society his paper on the 'Connection of Volcanic Phenomena with the Elevation of Mountain Chains,' when, says Lyell admiringly in a private letter, 'he opened upon De la Beche, Phillips, and others'—the veterans of the science—'his whole battery of the earthquakes and volcanoes of the Andes.' Shortly after, the audacious young man was appointed secretary to the Geological Society, a post which he filled when the voyage of the 'Beagle' was first published in 1839.
In the early part of that same year, the rising naturalist took to himself a wife from one of the houses to which he himself owed no small part of his conspicuous greatness. His choice fell upon his cousin, Miss Emma Wedgwood, daughter of Josiah Wedgwood, of Maer Hall; and, after three years of married life in London, he settled at last at Down House, near Orpington, in Kent, where for the rest of his days he passed his time among his conservatories and his pigeons, his garden and his fowls, with his children growing up quietly beside him, and the great thinking world of London within easy reach of a few minutes' journey. His private means enabled him to live the pleasant life of an English country gentleman, and devote himself unremittingly to the pursuit of science. Ill health, indeed, interfered sadly with his powers of work; but system and patience did wonders during his working days, which were regularly parcelled out between study and recreation, and utilised and economised in the very highest possible degree. Early to bed and early to rise, wandering unseen among the lanes and paths, or riding slowly on his favourite black cob, the great naturalist passed forty years happily and usefully at Down, where all the village knew and loved him. A man of singular simplicity and largeness of heart, Charles Darwin never really learnt to know his own greatness. And that charming innocence and ignorance of his real value made the value itself all the greater. His moral qualities, indeed, were no less admirable and unique in their way than his intellectual faculties. To that charming candour and delightful unostentatiousness which everybody must have noticed in his published writings, he united in private life a kindliness of disposition, a width of sympathy, and a ready generosity which made him as much beloved by his friends as he was admired and respected by all Europe. The very servants who came beneath his roof stopped there for the most part during their whole lifetime. In his earlier years at Down, the quiet Kentish home was constantly enlivened by the visits of men like Lyell, Huxley, Hooker, Lubbock, and Wollaston. During his later days, it was the Mecca of a world-wide scientific and philosophic pilgrimage, where all the greatest men our age has produced sought at times the rare honour of sitting before the face of the immortal master. But to the very last Darwin himself never seemed to discover that he was anything more than just an average man of science among his natural peers.
Shortly after Darwin went to Down he began one long and memorable experiment, which in itself casts a flood of light upon his patient and painstaking method of inquiry. Two years before, he had read at the Geological Society a paper on the 'Formation of Mould,' which more than thirty years later he expanded into his famous treatise on the 'Action of Earthworms.' His uncle and father-in-law, Josiah Wedgwood, suggested to him that the apparent sinking of stones on the surface might really be due to earthworm castings. So, as soon as he had some land of his own to experiment upon, he began, in 1842, to spread broken chalk over a field at Down, in which, twenty-nine years later, in 1871, a trench was dug to test the results. What other naturalist ever waited so long and so patiently to discover the upshot of a single experiment? Is it wonderful that a man who worked like that should succeed, not by faith but by logical power, in removing mountains?
Unfortunately, we do not know the exact date when Darwin first read Malthus. But that the perusal of that remarkable book formed a crisis and turning-point in his mental development we know from his own distinct statement in a letter to Haeckel, prefixed to the brilliant German evolutionist's 'History of Creation.' 'It seemed to me probable,' says Darwin, speaking of his own early development, 'that allied species were descended from a common ancestor. But during several years I could not conceive how each form could have been modified so as to become admirably adapted to its place in nature. I began therefore to study domesticated animals and cultivated plants, and after a time perceived that man's power of selecting and breeding from certain individuals was the most powerful of all means in the production of new races. Having attended to the habits of animals and their relations to the surrounding conditions, I was able to realise the severe struggle for existence to which all organisms are subjected; and my geological observations had allowed me to appreciate to a certain extent the duration of past geological periods. With my mind thus prepared I fortunately happened to read Malthus's "Essay on Population" and the idea of natural selection through the struggle for existence at once occurred to me. Of all the subordinate points in the theory, the last which I understood was the cause of the tendency in the descendants from a common progenitor to diverge in character.'
It is impossible, indeed, to overrate the importance of Malthus, viewed as a schoolmaster to bring men to Darwin, and to bring Darwin himself to the truth. Without the 'Essay on the Principle of Population' it is quite conceivable that we should never have had the 'Origin of Species' or the 'Descent of Man.'
At the same time, Darwin had not been idle in other departments of scientific work. Side by side with his collections for his final effort he had been busy on his valuable treatise upon Coral Reefs, in which he proved, mainly from his own observations on the Keeling archipelago, that atolls owe their origin to a subsidence of the supporting ocean-floor, the rate of upward growth of the reefs keeping pace on the whole with the gradual depression of the sea-bottom. 'No more admirable example of scientific method,' says Professor Geikie forty years later, 'was ever given to the world; and even if he had written nothing else, this treatise alone would have placed Darwin in the very front of investigators of nature.' But, from our present psychological and historical point of view, as a moment in the development of Darwin's influence, and therefore of the evolutionary impulse in general, it possesses a still greater and more profound importance, because the work in which the theory is unfolded forms a perfect masterpiece of thorough and comprehensive inductive method, and gained for its author a well-deserved reputation as a sound and sober scientific inquirer. The acquisition of such a reputation, afterwards increased by the publication of the monograph on the Family Cirripedia (in 1851), proved of immense use to Charles Darwin in the fierce battle which was to rage around the unconscious body of the 'Origin of Species.' To be 'sound' is everywhere of incalculable value; to have approved oneself to the slow and cautious intelligence of the Philistine classes is a mighty spear and shield for a strong man; but in England, and above all in scientific England, it is absolutely indispensable to the thinker who would accomplish any great revolution. Soundness is to the world of science what respectability is to the world of business—the sine qua non for successfully gaining even a hearing from established personages.
To read the book on Coral Reefs is indeed to take a lesson of the deepest value in applied inductive canons. Every fact is duly marshalled: every conclusion is drawn by the truest and most legitimate process from careful observation or crucial experiment. Bit by bit, Darwin shows most admirably that, through gradual submergence, fringing reefs are developed into barrier-reefs, and these again into atolls or lagoon islands; and incidentally he throws a vivid light on the slow secular movements upward or downward for ever taking place in the world's crust. But the value of the work as a geological record, great as it is, is as nothing compared with its value as a training exercise in inductive logic. Darwin was now learning by experience how to use his own immense powers.
Meanwhile, the environment too had been gradually moving. In 1832, the year after young Darwin set out upon his cruise, Lyell published the first edition of his 'Principles of Geology,' establishing once for all the uniformitarian concept of that branch of science. In 1836, the year when he returned, Rafinesque, in his 'New Flora of North America,' had accepted within certain cramping limits the idea that 'all species might once have been varieties, and that many varieties are gradually becoming species by assuming constant and peculiar characters.' Haldeman in Boston, and Grant at University College, London, were teaching from their professorial chairs the self-same novel and revolutionary doctrine. At last, in 1844, Robert Chambers published anonymously his famous and much-debated 'Vestiges of Creation,' which brought down the question of evolution versus creation from the senate of savants to the arena of the mere general public, and set up at once a universal fever of inquiry into the mysterious question of the origin of species. Chambers himself was a man rather of general knowledge and some native philosophical insight than of any marked scientific accuracy or depth. His work in its original form displayed comparatively little acquaintance with the vast groundwork of the question at issue—zoological, botanical, geological, and so forth—and in Charles Darwin's own opinion showed 'a great want of scientific caution.' But its graphic style, its vivid picturesqueness, and to the world at large the startling novelty of its brilliant and piquant suggestions, made it burst at once into an unwonted popularity for a work of so distinctly philosophical a character. In nine years it leaped rapidly through no less than ten successive editions, and remained until the publication of the 'Origin of Species' the chief authoritative exponent in England of the still struggling evolutionary principle.