There is no similar periodic process in human conscious experience considered independently of any spatial objects it might represent.

In the transcendental argument of the Refutation of Idealism, Kant’s target is not Humean skepticism about the applicability of a priori concepts, but rather Cartesian skepticism about the external world. This argument was added by Kant to the second edition of the Critique of Pure Reason (B274–279, with a change suggested in the Preface to B, Bxxxix–Bxli), and subsequently embellished and reworked in a series of Reflections (Guyer 1987: 279–316). More specifically, Kant intends to refute what h