ling with the _a priori_ judgements of mathematics, which
relate to the sensibility, and the latter dealing with the _a priori_
principles of physics, which originate in the understanding. Again,
within each of these two divisions we have to distinguish two
problems, viz. 'What _a priori_ judgements are essentially related to
the faculty in question?' and 'How is it that they are applicable to
objects?'

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.

[13] B. 74-5, M. 45-6; cf. pp. 27-9.

[14] B. 160 note, M. 98 note.

CHAPTER III

SPACE

It is the aim of the _Aesthetic_ to deal with the _a priori_ knowledge
which relates to the sensibility. This knowledge, according to Kant,
is concerned with space and time. Hence he has to show _firstly_ that
our apprehension of space and time is _a priori_, i. e. that it is not
derived from experience but originates in our apprehending nature; and
_secondly_ that within our apprehending nature this apprehension
belongs to the sensibility and not to the understanding, or, in his
language, that space and time are forms of perception or sensibility.
Further, if his treatment is to be exhaustive, he should also show
_thirdly_ that space and time are the only forms of perception. This,
however, he makes no attempt to