Picking Out the a Priori

The classic distinction between a priori and a posteriori justification is that subjects justified a priori are justified independently of experience, while subjects justified a posteriori are justified by appeal to at least some experience-based evidence. Recently, the coherence of the distinction between experiential and non-experiential evidence has been challenged by Michael Devitt 1 and Albert Casullo. The worry is that, without a coherent, positive articulation of the difference between experiential and non-experiential evidence of the sort relevant for a priori justification, we lack a reason to take a priori justification seriously. This "distinction challenge" places a burden on the rationalist to say just what non-experiential evidence would be if there were such a thing. This article reviews the problem, critique BonJour's and Cusullo's proposed solutions, and conclude by offering accounts of experiential and non-experiential evidence that meet the distinction challenge, avoid criticisms of extant attempts, and beg no questions against rationalists or empiricists. Even if this particular solution is not acceptable to everyone in the debate, it suggests a straightforward framework for meeting the distinction challenge.