Sigmund Freud , born Sigismund Schlomo Freud (6 May 1856 – 23 September 1939), was an Austrian neurologist who founded the psychoanalytic school of psychiatry. Freud is best known for his theories of the unconscious mind and the defense mechanism of repression, and for creating the clinical practice of psychoanalysis for treating psychopathology through dialogue between a patient, technically referred to as an "analysand", and a psychoanalyst. Freud redefined sexual desire as the primary motivational energy of human life, developed therapeutic techniques such as the use of free association, created the theory of transference in the therapeutic relationship, and interpreted dreams as sources of insight into unconscious desires. He was an early neurological researcher into cerebral palsy, and a prolific essayist, drawing on psychoanalysis to contribute to the history, interpretation and critique of culture.