APPERCEPTION. - A term Leibniz (v.), who, by distinguishing between perception and a., claimed to avoid the difficulties encountered by both the Cartesians and Locke: whereas perception is the inner state of the monad in representing external things, a. is the consciousness or reflective knowledge of this inner state and belongs to the more perfect entelechies or souls (Principi della Natura e della Grazia, § 4, Italian trans., Bari 1912, p. 234).
In Kant, on the other hand, a. rises to the supreme function of the understanding, as the transcendental “I think”: it must accompany all representations as the synthetic a priori unity of the manifold which precedes and grounds all other forms of unification. Just as the synthesis of representations presupposes the a priori unity given by the categories (v.), so the synthesis of the categories presupposes that of the “I think,” from which they derive (Critica della ragion pura, §§ 15-20).
In Herbart, a. denotes the psychological dynamism by which new material is assimilated to past experience in an organized whole. In W. Wundt, a. is both the actual synthesis of experience and the principle of the synthesis effected by feelings (creative synthesis); and it is passive when unification is perceived as something “undergone,” active when it involves on the subject’s part preparatory processes such as attention, expectation, completion, and the like (Grundriss der Psychologie, 4th ed., Leipzig 1901, § 15, pp. 250, 260-61).