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 such a subject, he took the dare, and wrote his Social Statics. It had only a small sale, but it won him access to the magazines. In 1852 his essay on "The Theory of Population"

(one of the many instances of Malthus' influence on the thought of the nineteenth century) suggested that the struggle for existence leads to a survival of the fittest, and coined those historic phrases. In the same year his essay on "The Development Hypothesis" met the trite objection—that the origin of new species by progressive modification of older ones had never been seen—by pointing out that the same argument told much more strongly against the theory of the "special creation" of new species by God; and it went on to show that the development of new species was no more marvelous or incredible than the development of a man from ovum and sperm, or of a plant from a seed. In 1855 his second book, The Principles of Psychology, undertook to trace the evolution of mind. Then, in 1857, came an essay on "Progress, Its Law and Cause," which took up Von Baer's idea of the growth of all living forms from homogeneous beginnings to heterogeneous developments, and lifted it into a general principle of history and progress. In short Spencer had grown with the spirit of his age, and was ready now to become the philosopher of universal evolution.

When, in 1858, he was revising his essays for collective publication, he was struck by the unity and sequence of the ideas he had expressed; and the notion came to him, like a burst of sunlight through opened doors, that the theory of evolution might be applied in every science as well as in biology; that it could explain not only species and genera but planets and strata, social and political history, moral and esthetic conceptions. He was fired with the thought of a series of works in which he would show the evolution of matter and mind from nebula to man, and from savage to Shakespeare. But he almost despaired when he thought of his nearly forty years. How could one man, so old, and an invalid, traverse all the sphere of human knowledge before his death? Only three