Prkis of Perception and Reason'1

Abstract

What is the role of conscious perceptual experience in making thought about the mind-independent empirical world possible? What is the role of such experience in the acquisition of empirical knowledge about the way things are in that world? What is the relation between these two roles? My central argument is intended to establish that a proper account of the way in which perceptual experience is essential to our grasp of determinate thoughts about particular things in the world around us will at the same time yield a full explanation of the fundamental role which such experience plays in the acquisition of empirical knowledge, by providing us with reasons, which we recognize as such, to endorse the most basic thoughts about mind-independent things in belief. The empirical world is a world of persisting, spatially extended and located particulars and their changing properties over time. I take it for granted that we refer to such things in thought-in the most basic cases, when we perceive them in our current environment-and that we frequently know that we are doing so. Consider a person, S, with a perceptually-based belief about a particular mind-independent thing, a; and suppose that S actually knows that he is referring to a. Assume, for reductio, that S's Idea of a is purely descriptive.2 That is, his conception of which thing a is is exhausted by a wholly general description, 'The F', which purports to identify a by reference to its own properties and its spatial and other relations with other things which are also identified purely descriptively. Thus, his entertaining the Idea is quite independent of any experience of the object in question. However detailed and extensive this description of a may be, though, it is bound to be an epistemic possibility for S that 'F' is multiply satisfied, in the following sense. It is logically consistent with all that S knows that 'F' is satisfied by more than one thing. For he cannot knowledgeably rule out the possibility of a massive qualitative reduplication elsewhere in the universe of the relevant