In Die Traumdeutung (1900) , translated as The Interpretation of Dreams (1953), Freud, Sigmund borrows this term from geography (where it refers to a type of map that distinguishes between features such as mountains and lakes and specifies their exact height or depth), to describe his conception of the psychical apparatus as consisting of three distinct regions: the unconscious, the preconscious, and the conscious. Freud did not intend this to be a form of anatomical localization, to specify one part of the brain as being unconscious and another conscious, which is why he is careful to use the term psychical apparatus to describe what he is talking about. He adopted the notion of topography because his analysis of patients suggested very strongly to him that the kinds of impulses, thoughts, and wishes he associated with the unconscious occur on a different stage to those of the conscious. This hypothesis is effectively the starting premise of psychoanalysis: the unconscious is a different kind of psychical mechanism to the conscious and its productions can only pass into the conscious if they are distorted and transformed by the primary processes (i.e. the dreamwork). Except for the occasional, unwelcome intrusions, which Freud termed parapraxis (better known as âFreudian slipsâ), the conscious is generally unaware of what is happening in the unconscious, but the constant pressure of the repression it has to apply to remain ignorant takes its toll. Freud produced a second topography late in his career replacing the terms unconscious, preconscious, and conscious with the terms id, ego, and superego, but retaining the idea of their spatial separation. The main difference, though, between the two topographies is that in the second, Freud allowed that certain psychical impulses may occur in two or more regions simultaneously, whereas previously he had thought they originated in the unconscious and migrated to the conscious.