Abstract

According to "skepticism about the external world", one cannot know whether there are any things that have these two characteristics: they exist, or occur, at, or come from, some place, and they might have existed even had no one been conscious of them. In attempting to show that one cannot know whether or not there are any such things, the skeptic appeals to the alleged fact that one cannot rule out various possibilities, e.g., the possibility that one is dreaming. But, if one cannot rule out these possibilities, then how can one even have any grounds for believing that there are such things? I show how certain attempts to explain how one can have such grounds cannot succeed, and I offer an alternative that does succeed. This alternative depends upon a certain analysis of the notion of sensory experience. After providing that analysis, and showing how, by appeal to it, we can explain not only how it is possible to have grounds for believing that there are external things, but how it is possible to know that there are, I explain why it is that philosophers have failed to appreciate the possibility of providing such an explanation. In offering this explanation, I also explain why it is that skepticism about the external world, as well as various other philosophical doctrines, is subject to what I call "instability"