It is commonly accepted by Kant scholars that Kant held that all necessary truths are a priori, and all a priori knowledge is knowledge of necessary truths. Against the prevailing interpretation, I argue that Kant was agnostic as to whether necessity and a priority are co-extensive. I focus on three kinds of modality Kant implicitly distinguishes: formal possibility and necessity, empirical possibility and necessity, and noumenal possibility and necessity. Formal possibility is compatibility with the forms of experience; empirical possibility is compatibility with the causal powers of empirical objects; noumenal possibility is compatibility with the causal powers of things in themselves. Because we cannot know the causal powers of things in themselves, we cannot know what is noumenally necessary and what is noumenally contingent. Consequently, we cannot know whether noumenal necessity is co-extensive with a priority. Therefore, for all we know, some a priori propositions are noumenally contingent, and some a posteriori propositions are noumenally necessary. Thus, contrary to the received interpretation, Kant distinguishes epistemological from metaphysical modality.