This paper offers a new interpretation of Kant's puzzling claim that the B-Deduction in the Critique of Pure Reason should be considered as having two main steps. Previous commentators have tended to agree in general on the first step as arguing for the necessity of the categories for possible experience, but disagree on what the second step is and whether Kant even needs a second step. I argue that the two parts of the B-Deduction correspond to the two aspects of a priori cognition: necessity and universality. The bulk of the paper consists of support for the second step, the universality of the categories. I show that Kant's arguments in the second half of the B-Deduction aim to define the scope of that universality for possible experience by considering the possibilities of divine intellectual intuition, of non-human kinds of sensible intuition, and of apperception of the self. In these ways Kant delimits the boundaries of the applicability of the categories and excludes any other possible experience for human beings.