ABSTRACT The paper reinterprets Kant’s Copernican revolution as a transcendental-psychological transformation in the approach to metaphysics. It tackles the prevalent scholarly view that Kant’s theory of the faculty of cognition appears incompatible with his broader metaphysical framework of transcendental idealism, primarily due to difficulties in integrating cognitive faculties such as sensibility and understanding within the dichotomy of appearances and things in themselves. The paper proposes that Kant’s transcendental psychology is neither a metaphysical-rational doctrine of the noumenal mind, nor an empirical-naturalized study of the phenomenal mind. Instead, it presents a theory centered on the transcendental subject as an abstract entity, positing it as the hypothetical bearer of the cognitive functions necessary for all potential finite cognizers, with humans exemplifying a particular empirical realization. While empirical realizations of cognitive functions manifest through temporal-causal mechanisms, their transcendental grounds consist of abstract functional structures defined by unschematized categories. These transcendental functions, which determine the necessary conditions for objective cognition, also inherently define the fundamental structure of all possible objects of cognition. Kant’s metaphysical inquiry into the structure of reality is thus conducted through an examination of the faculty of cognition, showcasing a revolutionary transcendental-psychological approach to metaphysics.