Topology refers primarily to the branch of mathematics that rigorously treats questions of neighborhoods, limits, and continuity. Psychoanalysts have applied it to the study of unconscious structures.

In what have been called his two "topographies" (the first dating from 1900 and the second from 1923), Freud resorted to schemas to represent the various parts of the psychic apparatus and their interrelations. These schemas implicitly posited an equivalence between psychic and Euclidean space.

Early on, Jacques Lacan noted that the limitations of such a naive topology had restricted Freudian theory, not only in the description of the psychic apparatus (a description that in the end required an appeal to the economic point of view), but also in the specificity of clinical structures. The hypothesis that the unconscious is structured like a language, that is, in two dimensions, led Lacan to the topology of...