A Priori Bootstrapping

A sceptical scenario is a situation in which your experiences are in some undetectable way unreliable guides to the truth - say, because you are being deceived by a demon (or the like). According to a certain sceptical argument, you cannot have any justification for believing the proposition that you are not in a sceptical scenario, since such justification would have to be either a priori or empirical, but neither a priori nor empirical justification for this proposition is available. In fact, however, if you are justified in believing ordinary propositions about the external world on the basis of your experiences, it follows that you also have a priori justification for believing that you are not in a sceptical scenario. If experiences justify ordinary beliefs in this way, then there is at least one possible process of non-empirical reasoning - the "a priori bootstrapping reasoning" - that can lead you to a justified belief in the proposition that you are not in a sceptical scenario. This point leaves open the question of why experiences justify ordinary beliefs; but it seems to provide an answer to the sceptical argument, and it helps to illuminate the nature of a priori justification.