Sigmund Freud is regarded as the father of psychodynamic theories, the founder of psychoanalysis and the creator of psychosexual stages theory of human development.

Regardless of the acceptance or disapproval of his ideas about human development, his influence over psychology was enormous. During a puritan era he managed to construct a theory of unconscious motivation, of human sexuality and instinctual aggression.

Erikson was a stage theorist who took Freud’s controversial theory of psychosexual development and modified it as a psychosocial theory, as he rejected the central importance of the sexual drive in favour of the progressive emergence of identity. Like Freud and many others, Erik Erikson maintained that personality develops in a predetermined order, and builds upon each previous stage. This is called the epigenetic principle.