Herbert Spencer is chiefly remembered as an evolutionary philosopher, as one of the founders of sociology, and as a defender of a libertarian version of classical liberalism. He described the evolutionary process and applied it to psychology and biology prior to the publication of Charles Darwin's On the Origin of Species by Means of Natural Selection, or, The Preservation of Favoured Races in the Struggle for Life in 1859. Even after the publication of that work Spencer never abandoned the Lamarckian notion that the primary thrust behind evolutionary development is the inheritance of characteristics acquired during the life of the organism through use and disuse. The recognition by biologists that such inheritance is not part of biological evolution has proved to be a fatal flaw in his biological work. In psychology, however, Spencer's ideas proved revolutionary. Moving beyond the associationism of Joseph Priestley and James Mill, he insisted that...