 Kant does occasionally say that the actualization of the apperceptive power, in the synthetic unity of understanding, depends on the use of the categories (e.g., B145-6). This might make Kant’s account seem circular, with the understanding depending on apperception which in turn depends on the understanding, as the faculty of synthesis. But Kant can hold that while the power or faculty of pure apperception is distinct from any of its actualizations, when it is so actualized it entails a synthetic combination via the categories (B143, B144). Thus the fact that apperception does not occur without the categorial synthesis doesn’t mean that apperception is grounded in such synthesis. This way Kant can both say that the understanding is made possible by the power of apperception, and that apperception (as actualized unity) depends on—in the sense that it cannot actualize without—conceptual/categorial synthesis.