Here is my impression: it is very popular to allow certain kinds of experiences to provide (prima facie propositional) justification for certain propositions. Which propositions might an experience justify? The most straightforward thing to say is that certain experiences provide justification for their propositional contents; but if experiences don’t have propositional contents, some more elaborate story will need to be told. For the sake of simplicity, I’ll assume that an experience justifies a proposition only if it has a propositional content.
Which experiences provide justification for their propositional contents? Here are some popular answers: perceptual experiences, memorial experiences, a priori intuitions, or some combination thereof. (I am thinking of a priori intuitions as experiences. Intuitions about morality, math, modality, and philosophy often count as a priori intuitions.) It is not popular, however, to say that just any experience (or just any experience with a representational content) can justify its conclusion. But this raises the following questions: if some experiences justify their contents, why don’t all experiences justify their contents? What principled criterion is there for allowing only certain experiences (with contents) to justify their conclusions?
Reliabilists have a straightforward answer: only experiences that are caused in a reliable way can justify. Other externalists will have similar stories to tell. But what about the internalist? What criterion can he use to distinguish between experiences that justify and those that don’t?
One answer is available to those who allow a priori intuitions to justify. They can say something like this: an experience that P justifies P just in case it is the result of possessing, or understanding, the concepts involved in P. The intuition that torture is wrong justifies because it results from possessing the concepts ‘torture’, ‘is’, ‘wrong’. The experience that the Cubs will win the World Series does not justify because it does not result possessing the concepts involved.
I’ve never found this explanation very appealing for two reasons. The first is essentially this argument: (i) perceptual experiences and a priori experiences justify; (ii) concept possession does not explain why perceptual experiences justify (at least not all of them); (iii) there is one explanation for why experiences justify (so if concept possession doesn’t explain why perceptual experiences justify, then it doesn’t explain why a priori intuitions justify); (iv) therefore, concept possession doesn’t explain why a priori intuitions justify. The second reason is that if you are going to give concept possession such a prominent role in a priori justification, a priori intuition doesn’t seem to do any work—it just seems along for the ride.
My own view on the matter is phenomenal conservatism: necessarily, if it seems to S that P, then S has (prima facie propositional) justification that P. A seeming that P is an experience with propositional content P and a special kind of phenomenal character. The phenomenal character “assures” the subject that its content is true. Perceptual experiences, memorial experiences, and a priori intuitions are all plausible candidates for seemings. Phenomenal conservatism is unpopular because many find it implausible that all seemings provide justification. Surely, some argue, a seeming produced by wishful thinking has no justificatory power.
Here is another way of pressing the question in which I’m interested: if some seemings justify, why don’t all seemings justify? It seems that many internalists allow perceptual and a priori seemings to justify, but they don’t allow wishfully-produced seemings to justify. What principled, internalist criterion can allow only some (and the right ones) to justify?