Abstract

I argue in favor of the possibility of real a priori justification. Some writers have claimed that, to adequately defend against the naturalist, we should grant that a priori justification can be defeated by further experiential evidence. Such writers generally view a priori faculties as on a par with empirical faculties but with different proper objects. While perceptual objects are the contingently existing things with which we are in causal contact, a priori objects are either necessarily true propositions or necessarily existing abstract objects with which we are not in causal contact. ;Though I admit that there is a weak sense of a priori justification according to which an a priori justified belief can become irrational in the face of experiential evidence, I argue that genuine a priori justification cannot be overridden by further experiential considerations . Allowing that a priori justification admits of degrees, we can be more or less a priori justified in a belief, depending on the extent to which that belief is revisable in the face of experiential evidence. In this way, I argue that the naturalist, in saying that a priori justification can always be defeated by experiential evidence, does not impugn the possibility that some beliefs can have a greater degree of a priori justification than others . I further argue that experiential beliefs derive much of their justification from a large background network of beliefs with a high degree of a priori justification. Some inference rules, I argue, in licensing the revision of empirical beliefs, must be unrevisable in their own right. Thus, if the naturalist is right, and a priori justification does require mysterious, occult processes, then so does experiential justification. If mysterious, occult processes are to be avoided at all costs, naturalism commits us to a rather extreme form of philosophical skepticism