sigmund freud (1856-1939)

Sigmund Freud was a physiologist, doctor, psychologist and the founder of psychoanalysis.  he Worked initially in Joseph Breuer and Freud elaborated the theory that the mind is a complex energy-system.  He expressed and refined the concepts of the unconscious, infantile sexuality, repression, and proposed a tri-partite account of the mind's structure.  This was as part of a new way of understanding human psychological development and the treatment of abnormal mental conditions. 

Freud's theory of infantile sexuality does not just concern sexuality but is an integral part of a theory of human personality.