What is Freud’s contributions to psychology?

Sigmund Freud is a key figure in the history of psychology. His contributions to personality theory still dominate contemporary theory about the human personality.  Once Freud told a story about an incident in his private practice. As a certain patient left the office after the appointment with Freud, he said, "I’ll play you later, Dr. Freud. Oh, that is, I’ll pay you later.’ Freud said that the seemingly accidental slip of the tongue revealed an unconscious intention. The man did not want to pay Freud for his service and was only "playing" with him. The patient never paid his bill.
     The story reveals some important things about both Freud and his theories. Although Freud was in private practice, his primary interest was not money. He was interested in theory and would have preferred an academic post. He had difficulties because of the fact that he was a Jew, and private practice was a second-best alternative. The story also illustrates the fact that Freud was a determinist. That is, he believed everything is caused. Even seemingly careless errors such as slips of the tongue have a meaning which suggests that the motive exists outside of the center of consciousness. This is a central concept of Freudian theory -- unconscious motives. And people do not always know why they do and what they do.