The Scope of Perceptual Knowledge

Seeing, hearing, feeling, smelling or tasting that something is so, are all forms of sense-perceptual knowledge (which, hereafter, I call simply perceptual knowledge). I shall be concerned with perceptual knowledge in its primary sense on which it satisfies the following perceived-object condition: If you perceive that A is an F (or is G) then you perceive A. There are conceptions of perceptual knowledge on which this condition is not met. Dretske, for example, has suggested that there is a sense of ‘seeing that’ on which a traffic officer may see that a driver was exceeding the speed limit by seeing that tyre marks, produced by sudden braking action, are of a certain length. Though in this sense the officer sees that the driver was exceeding the limit, he need not see the driver. I shall not take issue with this way of thinking. Granted that the knowledge illustrated by Dretske’s example is, in some sense, perceptual, it clearly depends on perceptual knowledge which satisfies the perceived-object condition. Dretske’s traffic officer relies on knowing that the tyre marks, which he sees, are of a certain length. Even with the restriction to perceptual knowledge in the primary sense there is a substantive issue concerning the scope of perceptual knowledge. A plausible way of conceiving of such knowledge treats it as satisfying at least the following conditions: