Apperception is usually defined as the mental process that raises subconscious or indistinct impressions to the level of attention and at the same time arranges them into a coherent intellectual order. The term apperception, however, has been used ambiguously, sometimes to mean merely consciousness or awareness, at other times to mean the acts of concentration and assimilation. Inevitably, a process of such significance has implicitly and explicitly been dealt with by philosophers ever since they first concerned themselves with the cognitive process. Aristotle, the Church Fathers, and the Scholastics all distinguished between vague notions and feelings on the one hand, and conceptions brought about by an act of intellectual willing on the other.

Descartes

The concept of apperception (in the form of the verb apercevoir) appears in René Descartes's Traité des passions.

Later writers generally use the term perception for denoting a state of dim awareness. So John...