APPERCEPTION. – A term that came into use with Leibniz (v.), who distinguished between perception and apperception to avoid the difficulties encountered by both Cartesians and Locke: while perception is the inner state of the monad in representing external things, apperception is the consciousness or reflexive knowledge of this inner state and belongs to entelechies or more perfect souls (Principles of Nature and Grace, § 4, Italian trans., Bari 1912, p. 234).
In Kant, on the other hand, apperception rises to the supreme function of understanding, as the “I think” transcendental; it must accompany all representations as the synthetic unity a priori of the manifold that 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 (Critique of Pure Reason, §§ 15–20).
In Herbart, apperception denotes the psychological dynamism of assimilating new material into past experience into an organized whole. In W. Wundt, apperception is both the factual synthesis of experience and the principle of the synthesis effected by feelings (creative synthesis); it is passive apperception when the unification is experienced as a “suffering,” active when it involves processes of preparation on the part of the subject such as attestation, expectation, completion, and the like (Grundrisse der Psychologie, 4th ed., Leipzig 1901, § 15, pp. 250, 260–61).