The work of Sigmund Freud (1856-1939), the Austrian founder of psychoanalysis, marked the beginning of a modern, dynamic psychology by providing the first systematic explanation of the inner mental forces determining human behavior.

Early in his career Sigmund Freud distinguished himself as a histologist, neuropathologist, and clinical neurologist, and in his later life he was acclaimed as a talented writer and essayist. However, his fame is based on his work in expanding man's knowledge of himself through clinical researches and corresponding development of theories to explain the new data. He laid the foundations for modern understanding of unconscious mental processes (processes excluded from awareness), neurosis (a type of mental disorder), the sexual life of infants, and the interpretation of dreams. Under his guidance, psychoanalysis became the dominant modern theory of human psychology and a major tool of research, as well as an important method of psychiatric treatment which...