The psychodynamic understanding of the personality and its disorders rests heavily upon the study of t life cycle. The commonalities and similarities in the course of all lives make possible the generalizations and abstractions necessary for the scientific study of the personality. Although no two persons are identical and no life stories are the same, the basic themes are limited and it is the variations upon them that are infinite and inexhaustible. Behind their individual uniqueness all persons are born with physical endowments that are essentially alike and with similar biological needs that must be met.