EVOLUTION--DARWIN AND SPENCER
AT the very beginning of our second period stands the epoch- making work of Darwin, which was destined to revolutionize the whole science of life, and with it psychology. Not, of course, that the idea of evolution was altogether new. It was at least as old as Lucretius, and in recent times it had been put forward in one sphere or another by quite a number of distinguished writers--by Laplace (the originator of the "nebular hypothesis") in astronomy, by Hegel, Fourier and Comte in sociology, by Lyell (probably the most influential of all) in geology, and by Buffon, Lamarck, Goethe, St. Hilaire, Erasmus Darwin ( Charles Darwin's grandfather), and Herbert Spencer in biology. It was Charles Darwin, however, who, by the collection of a vast mass of facts in support of the hypothesis and the formulation of the precise biological mechanisms through which evolution manifested itself, gave the theory a truly scientific form, and, by stressing the continuity of development throughout organic life up to the human level, expressed it in a way that appealed at once both to the learned and the popular imagination.
The general features of Darwin's theory, together with the main circumstances that led him to propound it, are too