This is the sourcebook for one of the most significant movements in twentieth-century psychology.

"Two opposed points of view," John B. Watson wrote in 1925, "are still dominant in American psychological thinking: introspective or subjective psychology, and behaviorism or objective psychology." His statement is still true today. Reacting against traditional psychology's emphasis on feelings and introspection, and its lack of precise categories, Watson proposed a methodological approach to psychological problems that would be logical, precise, and scientific. Consciousness, he believed, was not a usable hypothesis: the proper subject of human psychology is the behavior of the human being. Behaviorism aimed to free psychology from elusive, vague concepts and establish it as a true natural science.