Scepticism, Externalism and Predictive Dimension of Knowledge Claims

Abstract

Ordinary knowledge claims are challenged by philosophical scepticism which holds that we are unable to exclude the possibilities of error involved in well-known sceptical alternatives (e.g., the brain-in-a-vat hypothesis). In order to explain how we can resist this challenge, first I compare philosophical and ordinary doubt. I point out that they do not differ in terms of the way they aim to undermine knowledge claims, but rather in the character of the alternatives to which they appeal. Thus, in ordinary contexts, philosophical sceptical alternatives should not be considered relevant because they are farfetched, not supported by any indication that they really might exist in the given circumstances. Since this point concerns the assertability rather than the truth of our knowledge claims, I further argue that while our evidential basis for their assertability is internal, their truth depends upon certain assumptions concerning the causal history of our beliefs, reliability of our cognitive abilities, success in identifying and excluding relevant alternatives, etc. In everyday knowledge attributions, these assumptions operate as externalist preconditions so that we may know something only if they are correct even without knowing that they are correct. Finally, I point out an implicit predictive dimension of our knowledge claims consistent with their fallibility: when we properly claim to know something, we do not imply impossibility of being mistaken, but rather hold that we are not wrong and that no sudden twist of future events will show us to be wrong.