This chapter compares Heidegger’s interpretation of Kant with that of the German Idealists. The German Idealists attempt to unify Kant’s faculty psychology by uncovering a “common root” that is the source of sensibility and understanding, where the common root is a homogenous capacity that nevertheless can generate the other faculties. Insofar as these interpretations rely on telling a causal story, where one faculty causes others to arise, they return to a pre-critical position that Kant would reject; on Kant’s critical philosophy, we are precluded from extending categories like causality to our faculties for cognition, since such faculties do not appear sensibly in our experience. The chapter argues that, while Heidegger also seeks a common root, he avoids this problem by insisting that the common root is heterogenous. His common root – the imagination – is a unification of three basic capacities, rather than a single, deeper capacity that causes the others. Thus, Heidegger does not seek a foundation for metaphysics that is beyond the bounds of what Kant thinks we can know; he works with the cognitive capacities that Kant already identifies, but seeks to explain more fully the structural interrelationships between those capacities.