ABSTRACT
Synopsis Reid’s theory of vision is the centrepiece of his theory of perception. The exposition of that theory is the concern of this chapter. Though visual perception is a fundamental source of our information about the primary qualities of the external world it is not the originating source of our conceptions of the primary qualities of extension, figure, magnitude, and motion. These originate from touch. Our visual perception of these qualities is, therefore, acquired, and the theory of the visual perception of these qualities is a theory of acquired perception. It is a theory of how visual appearances represent the primary qualities of objects in visual perception. Sight is, of course, the origin of our conception of the secondary quality of colour, to wit, a conception of some unknown cause of a visual sensation of colour. This sensation, which is the only sensation of vision, is insufficient as the sign of the primary qualities we perceive by sight. The visual signs of the primary qualities we perceive by sight are not sensations in the mind but physical impressions on the organ of sense, on the eye.
