 The issue of which kinds of cognitive success explain which other kinds of cognitive success is orthogonal to the issue of which particular cognitive successes explain which other particular cognitive successes. The former issue concerns whether, for instance, the property of knowledge is to be explained in terms of the relation of one thing being a reason for another, or whether the relation of being a reason for is to explained in terms of knowledge. But the latter issue concerns whether, for instance, I am justified in holding some particular belief—say, that the cat is on the mat—in virtue of my knowing various specific things, e.g., that my vision is working properly under the present circumstances, and that the object that I am looking at now is a cat, etc. This latter issue is at the heart of various epistemological regress puzzles, and we will return to it below. But those regress puzzles are largely independent of the issue of metaphysical priority being discussed here.