Herbert Spencer, an English philosopher-scientist, was---with the anthropologists Edward Burnett Tylor and Lewis Henry Morgan---one of the three great cultural evolutionists of the nineteenth century. A contemporary of Charles Darwin (see Vol. 5), he rejected special creation and espoused organic evolution at about the same time. He did not, however, discover, as did Darwin, that the mechanism for evolution is natural selection. He was immensely popular as a writer in England, and his The Study of Sociology (1873) became the first sociology textbook ever used in the United States. With the recent revival of interest in evolution, Spencer may receive more attention than he has had for many decades.