Psychoanalysis is a set of theories and therapeutic techniques that deal in part with the unconscious mind, and which together form a method of treatment for mental disorders. The discipline was established in the early 1890s by Sigmund Freud, whose work stemmed partly from the clinical work of Josef Breuer and others. Freud developed and refined the theory and practice of psychoanalysis until his death in 1939. In an encyclopedic article, he identified the cornerstones of psychoanalysis as "the assumption that there are unconscious mental processes, the recognition of the theory of repression and resistance, the appreciation of the importance of sexuality and of the Oedipus complex." Freud's colleagues Alfred Adler and Carl Gustav Jung developed offshoots of psychoanalysis which they called individual psychology (Adler) and analytical psychology (Jung), although Freud himself wrote a number of criticisms of them and emphatically denied that they were forms of psychoanalysis. Psychoanalysis was later developed in different directions by neo-Freudian thinkers, such as Erich Fromm, Karen Horney, and Harry Stack Sullivan.