It is important, however, to notice that the distinction between the sensibility and the understanding, in the form in which it serves as a basis for distinguishing the Aesthetic and the Analytic, is not identical with or even compatible with the distinction, as Kant states it when he is considering the distinction in itself and is not thinking of any theory which is to be based upon it. In the latter case the sensibility and the understanding are represented as inseparable faculties involved in all knowledge.[13] Only from the union of both can knowledge arise. But, regarded as a basis for the distinction between the Aesthetic and the Analytic, they are implied to be the source of different kinds of knowledge, viz. mathematics and the principles of physics. It is no answer to this to urge that Kant afterwards points out that space as an object presupposes a synthesis which does not belong to sense. No doubt this admission implies that even the apprehension of spatial relations involves the activity of the understanding. But the implication is really inconsistent with the existence of the Aesthetic as a distinct part of the subject dealing with a special class of a priori judgements.
FOOTNOTES
[1] Cf. B. 1, 29, 33, 74-5, 75, 92-4; M. 1, 18, 21, 45-46, 57.
[2] B. 29, M. 18
[3] For the sake of uniformity Vorstellung has throughout been translated by 'representation', though sometimes, as in the present passage, it would be better rendered by 'presentation'.
[4] B. 74-5, M. 45-6.
[5] Cf. p. 29, note 1.
[6] Kant's account implies that he has in view only empirical knowledge; in any case it only applies to empirical conceptions.
[7] This distinction within perception is of course compatible with the view that the elements so distinguished are inseparable.
[8] See p. 29, note 1.