Freud believed that the most powerful nd pervasive unconscious ideas underlying hysteria were sexual. He believed that sexual ideas that were unacceptable to the conscious mind, were just like other socially unaccepted ideas, they would be repressed and become part of the unconscious. This sexual nature of the unconscious is also called the Oedipal complex. He believed that all children were sexually attracted to their parent of the opposite sex and become rivals with the parent of the same sex for the love object they share in common. These repressed sexual ideas would then emerge in a disguised form in dreams and in neurotic symptoms.

Freud named the sexual drive libido. The main characteristic of libido is the gradual buildup and sudden decreas of excitation. Eating, drinking and elimination share a common pattern of excitation, there Freud regarded them as sexual, or libidinous. The stages of psychosexual development progresses from the oral stage in infancy, to the anal stage and then to the genital zones.