The author presents a broad view of the principal forces at work in twentieth-century psychiatry. He describes the approach of the various psychiatries--psychoanalytic, biological, behaviorist, social, interpersonal, and existential--to the diagnostic enterprise and the therapeutic enterprise. He finds twentieth-century diagnosis dominated by objective-descriptive psychiatry and therapy by the extraordinary growth of psychotherapy in the industrial nations. The newer psychotherapeutic methods have made the first systematic additions since Freud to our understanding of the ways in which personal change occurs.