In the first place, then, we have to review the growth and solidification of Mr. Spencer's thought — in other words, the elaboration, as exhibited in his earlier writings, of that conception of evolution which was to find its definite expression in the majestic series of works of which the Synthetic Philosophy is composed. Let us begin by making ourselves acquainted with the starting-point of his mental development — that is, with the general theory of things which was current during his early years, and under the influence of which, in common with all his contemporaries, he grew to man's estate.
The period of Spencer's youth and ripening manhood was a period of transition in scientific and philosophic thought. On the ushering in of the present century the old cosmology still held sway with unabated vigor, along with all those time-worn dogmas concerning human life and destiny which had grown up with it during ages of ignorance and superstition, and with which its own existence was now inextricably bound up. What that cosmology and what those dogmas meant is a matter of such common history that we need not linger over them here. Suffice it to say that the unquestioned doctrines of special creation, fixed types, and a recent origin of the universe, lay at the bottom of them all, and that it was in the light of those doctrines that the world and life and man were one and all interpreted.
But before the century had got far upon its way, signs began to manifest themselves of an approaching change in the higher regions of thought. The special-creation hypothesis and the postulate of the world's recent origin and rapid manufacture had served well enough so long as their field had remained uninvaded by the results of investigation — so long as they had not been confronted with definite facts. In perfect keeping with the little that had been known of the universe in the darkness of the middle ages, they required that no jot or tittle should be added to that knowledge, to hold their place secure. But this could no longer be. The time came when investigation grew active, and definite facts — angular, awkward, unpleasant facts, which (after their reprehensible manner) were irreverent enough to refuse to fit into the most sacred and deeply cherished theory — began to accumulate with startling rapidity. The result was that the old conception of things began, little by little, to fall into disrepute, and the theological edifice of ages was shaken at its very foundations. Science showed, with a conclusiveness which remained untouched by all the special pleading with which her arguments and revelations were assailed, that the popular assumptions about the age of the world were absolutely untenable; that the commencement of life, and even of human life upon our globe, so far from taking us back only a few paltry thousands of years, lay countless millions