Sigmund Freud (born Sigismund Schlomo Freud) May 6, 1856 - September 23, 1939; was an Austrian neurologist and psychiatrist who co-founded the psychoanalytic school of psychology. Freud is best known for his theories of the unconscious mind, especially involving the mechanism of repression; his redefinition of sexual desire as mobile and directed towards a wide variety of objects; and his therapeutic techniques, especially his understanding of transference in the therapeutic relationship and the presumed value of dreams as sources of insight into unconscious desires. He is commonly referred to as "the father of psychoanalysis" and his work has been highly influential--popularizing such notions as the unconscious, defense mechanisms, Freudian slips and dream symbolism - while also making a long-lasting impact on fields as diverse as literature (Kafka), film, Marxist and feminist theories, literary criticism, philosophy, and psychology. However, his theories remain controversial and widely disputed.