It is impossible to understand the present methods of English political thinking without some consideration of the theory of evolution. Both habits of mind, the Liberal and the Tory, have been able to employ it for their own purposes, and its influence upon Socialism at one extreme and Imperialism at the other {310} has been equally marked. Darwin's book, _The Origin of Species_, was published in 1859, and produced instantly a turmoil in science and religion. Its bearing upon politics was less obvious, and there are no traces of it in the speculations of such a philosophical Liberal as Mill. The man who did most to bring the theory to bear upon things other than biology was Herbert Spencer, who was anything but a politician. But the channels by which its influence was poured into the general mind had become, by the end of the century, too numerous for discrimination, and the pulpit, the Press, the stage, the platform, and popular literature of every kind were full of references to the struggle for existence and the survival of the fittest. For good and evil the idea of evolution had become part of the national stock. Stated in plain terms, Darwin's theory was that the old conception of man, as having been specially created by God in a state of blessedness from which he fell by his own sin, was false, and that he had in fact been gradually developed out of an inferior state to his present degree of perfection. Humanity, like every other living thing, had been developed, whether mechanically or by divine order was not important, by a constant struggle with environment. Individuals, varying among themselves, were placed under certain conditions of life, for which some were better suited than others. Those who were fittest for the particular environment survived, and transmitted their particular variations to their offspring. When a sufficient number of generations had lived and died, these variations or characters were permanently fixed in the stock, and a class or species had appeared on the earth, which was distinct from others, who in different environments had similarly developed different forms. This theory was connected, not only with experiments and observations in the field of biology, but with geological investigation and the system of historical examination of constitutions, systems of law, and social structure, which was becoming increasingly common in Darwin's day. All united to emphasize the idea of growth. The eighteenth century appeared to conceive of everything as stationary. The later {311} nineteenth century conceived of everything as in motion. The organisms which were healthy and vigorous were those which adapted themselves most successfully to their environment, fixed new characters in their stocks, and rose from a lower condition to a higher.