An adjective for thought processes not present---or not visible---in the field of consciousness at a given moment in time. When Freud, Sigmund adopted the term, at a very early stage in his development of psychoanalysis, he transformed it from an adjective into a noun designating one of the three operative systems in the psychical apparatus (the other two being the preconscious and the conscious), as he refers to it in Die Traumdeutung (1900), translated as The Interpretation of Dreams (1953). As Freud conceives it, the unconscious is both a dynamic and a topography system: it is dynamic in the sense that the liminality energy and cathexis that are active within it are ceaseless---they apply a constant pressure on the preconscious and the conscious and are met in turn by an equally constant pressure (repression); it is topographical in that its processes and contents are only accessible to the conscious mind under very specific conditions, as though there were some kind of wall separating the different regions of the psychical apparatus. In his later years, Freud would modify his view slightly, but he basically held fast to the idea that the three different parts of the psychical apparatus are topographically distinct from one another and that contents of one region cannot pass directly into the next, but must undergo some kind of distortion or transformation as he details in his account of the dreamwork. Dreams, Freud famously said, are the royal road to the unconscious because they reveal its primary processes: condensation, displacement, and symbolization (a general term referring to the fact that the unconscious is the place where the instinct are given representational form). As a system, the unconscious is characterized by four main features: (i) the presence of these primary processes, and the corresponding flexibility and mobility of desire that goes with them; (ii) the absence of any kind of negation (there is no ânoâ in the unconscious, according to Freud); (iii) an indifference to reality (anything and everything is possible in the unconscious); and (iv) subordination to the pleasure principle. In the 1950s, at the height of structuralism, one of Freudâs most important interpreters, the French psychoanalyst Lacan, Jacques, developed the thesis that the unconscious is structured like a language. His rationale for this is the fact that, as Freud defines it, we can only grasp the processes of the unconscious when they take a linguistic form, but for them to be able to do this the unconscious has to already be structured like a language. Lacan also described the unconscious as the discourse of the Other, by which is meant the discourse of radical alterity---it is that which we cannot witness in full and that which transforms us insofar as we come into contact with it. Lacanâs account of the unconscious has been criticized for being overly linguistic, particularly by Deleuze, Gilles and Guattari, FĂ©lix who argue that the unconscious is better understood as a factory or machine.