In the Freudian metapsychology of the period of the first topography, the "Perception-Consciousness System" designates the system located on the periphery of the psychic apparatus. Its function is consciousness, and Freud linked it to the preconscious system.

The theoretical constitution of the Pcpt.-Cs. (Perception-Consciousness) system dates from the time of the "Project for a Scientific Psychology" (1950c [1895]). Gradually the Pcpt.-Cs. system was assimilated into the ego, or at least considered as its "core." Two clearly demarcated systems were needed to explain two contradictory functions—the inscription of (lasting) mnemic traces and their renewal—and this is what led Freud, following Breuer's observations, to distinguish between the Ucs.-Pcs. and the Pcpt.-Cs.

From the topographical point of view, the Pcpt.-Cs. system is attached to the Pcs. (preconscious) system but not to the Ucs. (unconscious) system—at...