We have been exploring the standard schema, as I called it, which Reid proposes for the analysis of what transpires in perception. The schema is this: The perceived entity evokes in the mind a sensation that is a sign of itself; this in turn evokes an apprehension of that entity and an immediate belief as to its external existence (or a belief which entails that). Here's how Reid himself states the schema in one passage: “The signs in original perception are sensations, of which nature hath given us a great variety, suited to the variety of the things signified by them. Nature hath established a real connection between the signs and the things signified; and nature hath also taught us the interpretation of the signs; so that, previous to experience, the sign suggests the things signified, and [immediately] creates the belief of it” (IHM VI, xxiv [195a; B 190]). Acquired perception differs from original perception in that whereas in the latter it's on account of an innate disposition that the sensation sign evokes the apprehension and belief, in the former it's on account of a disposition acquired in the course of experience.

One can thus think of perception, says Reid, as