Freud, Sigmund /froid/ [Austrian neurologist, 1856–1939] , founder of a complex integrated theory of psychological causes of mental disorders, some, such as hysteria, with physical symptoms. Among tenets of freudian theory are that human beings are motivated by a pleasure principle; receive internal stimulation from a sex instinct and a death instinct; have personality structures that can be divided into ego, superego, and id; and have unconscious, preconscious, and conscious levels of mental activity. See also freudian, freudian fixation, freudianism.
