Freud and Fliess, 1890. Sigmund Freud (May 6, 1856 - September 23, 1939) was an Austrian neurologist known as the founding father of psychoanalysis. In creating psychoanalysis, a clinical method for treating psychopathology through dialogue between a patient and a psychoanalyst. His analysis of dreams as wish-fulfillments provided him with models for the clinical analysis of symptom formation and the mechanisms of repression as well as for elaboration of his theory of the unconscious as an agency disruptive of conscious states of mind. Freud postulated the existence of libido, an energy with which mental processes and structures are invested and which generates erotic attachments, and a death drive, the source of repetition, hate, aggression and neurotic guilt. He died in 1939 at the age of 81 from cancer of the jaw. Wilhelm Fliess (October 24, 1858 - October 13, 1928) was a German Jewish otolaryngologist. He attended several conferences with Freud, and the two soon formed a strong friendship. Through their extensive correspondence and the series of personal meetings, Fliess came to play an important part in the development of psychoanalysis.