The document discusses Sigmund Freud's psychoanalytic theory of personality. It states that according to psychoanalysis, the main cause of behavior lies in the unconscious mind. It describes Freud's concepts of the id, ego, and superego - the three parts that make up his structural model of the psyche. The id operates on the pleasure principle, the ego mediates between the id, superego and environment using reality principle, and the superego internalizes societal values and ideals.