information:highlighting
1900–1940s

By 1936 the "Principle of Multiple Function" was clarified by Robert Waelder. He widened the formulation that psychological symptoms were caused by and relieved conflict simultaneously. Moreover, symptoms (such as phobias and compulsions) each represented elements of some drive wish (sexual and/or aggressive), superego, anxiety, reality, and defenses. Also in 1936, Anna Freud, Sigmund's daughter, published her seminal book, The Ego and the Mechanisms of Defense, outlining numerous ways the mind could shut upsetting things out of consciousness.