The a priori
a priori. Similarly, a student in a logic class might accept de Morgan’s laws on the basis of the teacher’s testimony and thus be justified in believing them empirically. Still, he might come to be justified in believing them a priori. One objection to D15 might be put this way: ‘‘(1) One needs some experience in order to form the concepts of a square, a rectangle, or a swan. (2) One needs some experience in order to grasp the propositions all squares are rectangles and all swans are swans. Therefore, (3) one’s belief is justified on the basis of some experience. And, therefore, (4) according to D15, one cannot be justified in believing them a priori.’’ In response, the proponent of D15 might point out that D15 does not imply that one can be justified a priori without having any experience at all. He might concede that one does need some experience to form the concepts of a square, a rectangle, and a swan and to understand the proposition that all squares are rectangles or all swans are swans. Still, even if some experience is needed to grasp a proposition, it does not follow that the proposition is justified by that experience or on the basis of any experience at all. If some experience is needed to grasp the proposition that all swans are swans, it does not follow that one’s belief in that proposition is justified on the basis of that experience. Consequently, the proponent of D15 will hold that (1) and (2) do not imply that either (3) or (4) is true. A proponent of D15 might concede, for example, that some experience is needed to grasp the proposition that all swans are under forty pounds. But again, from the fact that some experience enables you to grasp that proposition it does not follow that the proposition is justified for you by that experience. Let’s assume that various experiences enable me to grasp the proposition that all swans are under forty pounds. Still, I am not justified in believing it. I haven’t the faintest idea whether it is true. None of my experiences provide me with any reason to believe it. What would justify me in believing it is some experience I don’t yet have. So, again, from the fact that one has some experience that enables one to grasp a proposition, p, it does not follow that one is justified in believing that p on the basis of that experience or that one’s experience provides any reason to believe it is true. D15 seems quite promising. Still, it does face some objections. One objection concerns the connection between justification and experience. Consider, for example, certain forms of the coherence theory of justification. Pure coherence theories hold that all beliefs are justified solely in virtue of their relations to other beliefs, and that no beliefs are justified on
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