In treating of our subject three notions stand out prominently: the noumenon, the thing-in-itself and the transcendental object = X. In his commentary on The Transcendental Analytic, Robert P. Wolff has studied very carefully the question of the relationship between the notion of a transcendental object and that of the thing-in-itself. He noted and explained the passages of The Critique in which Kant means by the transcendental object simply the thing-in-itself and the passages in which he means by it something different such as “the concept of the ground of the unity of a manifold of representations in one consciousness.” There is little to be added, at this time, to Wolff's thorough investigations of this aspect of the problem.