_Chief Points of Hamilton's Theory of Perception._--All perception is immediate cognition; we perceive only what we apprehend as now and here existent; and hence what we perceive is either in our own organism, viewed as material, extended, etc., or else is in immediate correlation to it. The organism is, in perception, viewed as not-me; in sensation, as of the me. _What is given in Perception proper._--What we apprehend in perception proper is: 1. The primary qualities of body as pertaining to our own organism; 2. The secundo-primary qualities of bodies in correlation to it. (See Hamilton's division of qualities of bodies, as above.) _Primary Qualities of external Objects, how known._--The primary qualities of things external to our organism we do not perceive immediately, but only infer, from the effects produced on us by them. Neither in perception nor sensation do we apprehend immediately, or in itself, the external cause of our affection or sensation. That is always unknown to consciousness, known only by inference or conjecture. _External Existence, how learned._--The existence of the world without is apprehended not in a perception of the primary qualities of things external, but of the secundo-primary--_i. e._, in the consciousness that our movements are resisted by something external to our organism. This involves the consciousness of something external, resisting. The two things are conjunctly apprehended. _This presupposes what._--This experience presupposes the notion of space, and motion in space. These are inherent, instinctive native elements of thought, and it is idle to inquire how we come by them. Every perception of sensations _out of_, and distinct from, other sensations gives occasion for conceiving the idea of space. _Outness_ involves it.