Wilhelm Reich was an Austrian doctor of medicine and a psychoanalyst, a member of the second generation of analysts after Sigmund Freud. The author of several influential books, The Impulsive Character (1925), The Function of the Orgasm (1927), Character Analysis (1933), and The Mass Psychology of Fascism (1933), he became one of the most radical figures in the history of psychiatry.

Friedrich Salomon Perls, better known as Fritz Perls, was a German-born psychiatrist, psychoanalyst and psychotherapist. Perls coined the term "Gestalt therapy" to identify the form of psychotherapy that he developed with his wife, Laura Perls, in the 1940s and 1950s. Perls became associated with the Esalen Institute in 1964 and lived there until 1969.