ABSTRACT Recent work in philosophy of science has suggested that scientific paradigms in the wake of revolutions can be conceived as relativized a priori frameworks. In this paper, I put these accounts in dialog with two accounts of broadly “cultural” accounts of the relativized a priori in the history of philosophy: Ernst Cassirer's account of symbolic forms, on which, I show, the general “categories” stay the same but their expressions change, and Michel Foucault's account of the historical a priori, which is more thoroughly relativized than Cassirer's. I conclude that Foucault can offer helpful resources for philosophy of science insofar as the historical a priori admits of internal tensions that account for the possibility of a transition to a new a priori, and Foucault makes a similar, but more fully developed, appeal to social power than contemporary philosophy of science does in order to make sense of the changes between frameworks. Cassirer, on the other hand, helpfully puts emphasis on the cognitive activity of the subject, I rather than on the constitutive a priori principles themselves.