One of Sigmund Freud's contemporaries was Paul Federn. Federn wrote a book describing "Ego States" as a way of looking into the unconscious mind. unfortunately, the book is rather convoluted in style, and doesn't lend itself to application of therapy. Husband and wife team Dr's Jack And Helen Watkins of the University of Montana have brilliantly transposed the work into a powerful therapeutic tool called "Ego-State Therapy". This is a link to a web site which is rich with information about the Watkins'.

http://clinicalsocialwork.com/egostate.html