Cultural determinism is defined as a reaction against the biological determinism that was influential in nineteenth- and early twentieth-century Western anthropology. Environmental or cultural determinist criticism of biological determinism came from three sources: the behaviorists, a school in psychology; the cultural determinists, who were associated with the anthropologist Franz Boas; and postmodern anthropology and cultural relativism. The key arguments for cultural determinism, which was espoused by these schools, are explored, as are the most significant criticisms leveled against these arguments.