Freud called dreams the "royal road to the knowledge of the unconscious in mental life". This meant that dreams illustrate the "logic" of the unconscious mind. Freud developed his first topology of the psyche in "The Interpretation of Dreams" (1899) in which he proposed that the unconscious exists and described a method for gaining access to it. The preconscious was described as a layer between conscious and unconscious thought; its contents could be accessed with a little effort.