Believe it or not:
Freud's theory of the unconscious with respect to dream interpretation. Dreams, in Freud's view, were all forms of "wish-fulfillment" — attempts by the unconscious to resolve a conflict of some sort, whether something recent or something from the recesses of the past .
The Interpretation of Dreams is a book by psychoanalyst Sigmund Freud. The first edition (in German, and bearing the title Die Traumdeutung) was published in November 1899 (post-dated as 1900 by the publisher). The book inaugurated the theory of Freudian dream analysis, which activity Freud famously described as "the royal road to the understanding of unconscious mental processes."