Sigmund Freud 
The Ego and the Id [EPUB ebook] 

In what is considered one of his most prominent ideas, Austrian psychiatrist, Sigmund Freud explains the dynamic of the human psyche in terms of the roles and conflicts produced by the id, ego, and super-ego. Freud suggests that all human behaviors and traits, including personality disorders, are created by the complex conflicts and workings of these three components of human personality.