PERCEPTION. - It generally indicates the awareness of something in both external and internal experience and becomes almost synonymous with "consciousness" (v.): perception therefore involves a certain "judgment of existence" regarding the presence of an object (v.) in the field of consciousness. In a more rigorous sense, perception can be described as the complete act of concrete knowledge insofar as it brings about the synthesis of the sensory and intellectual spheres.
In pure sensation there is the presence of the quality (colors, sounds... shapes, movements), but with sensation alone (v.) one does not yet have the real "meaning" of the quality, which is obtained only in function of the "whole" subsequently grasped by the subject, which has its definitive expression in the "concept" (v.). But even the pure concept, such as the man who must abstract it from experience (v.) can have, cannot by itself attain the concrete, manifold and mutable, and therefore it pronounces only on the formal value of the contents of experience without grasping their reality of existence. Perception is the synthetic act of consciousness that actualizes and contains both movements in the dynamic unity of sensory consciousness and intellectual consciousness. In Thomist psychology, the perception of the singular existing thing, when it is a matter of objects of the external world, does not properly belong to the intellect as such, but insofar as it embraces sensibility in the unity of consciousness and is continued in particular with the cogitativa (v.), which is the internal sense proper to man, through which the intellect carries out the "conversio ad phantasmata" and therefore its conjunction with existing reality: in this sphere, accordingly, perception is immediate, though indirect ("Indirecte et quasi per quandam reflexionem...": Sum. Theol., 1a, q. 86, a. 1). In the spiritual life, on the other hand, man has immediate and direct perception of his acts and in the acts of his very existence (ibid., q. 87, aa. 1-4); and it must be called immediate and direct although it is secondary, insofar as it is conditioned by the apprehension of the objects to which consciousness first turns. Aristotle speaks of an "accessory" knowledge, ἐν πυρέψῃ (Met., XII, q. 1074, b 36), which St. Thomas clarified by seeking to bring it close to Augustinian interiority: "Et ideo id quod primo cognoscitur ab intellectu humano est huiusmodi obiectum, et secundario cognoscitur ipse intellectus cuius est perfectio ipsum intelligere" (Sum. Theol., 1a, q. 87, a. 3).
Modern psychology has oscillated between the elementary theory of perception through the association of ideas (v.) and the synthetic theory of Kantian derivation, which received an original interpretation in the "theory of form" (Gestalttheorie).
Bibliography
Cornelio Fabro