saying that Kant establishes the synthesis of the
manifold on certain principles by what are really two independent
lines of thought. The manifold may be regarded either as something
which, in order to enter into knowledge, must be given relation to an
object, or as something with respect to which self-consciousness must
be possible. Regarded in either way, the manifold, according to Kant,
involves a process of synthesis on certain principles, which makes it
a systematic unity. Now Kant introduces the categories by maintaining
that they are the principles of synthesis in question. "I assert that
the above mentioned _categories_ are nothing but the _conditions of
thinking in a possible experience_.... They are fundamental
conceptions by which we think objects in general for phenomena."[82]
A synthesis according to the categories is 'that wherein alone
apperception can prove _a priori_ its thorough-going and necessary
identity'.[83] In the first edition this identification is simply
asserted, but in the second Kant offers a proof.[84]

[82] A. 111, Mah. 204. Cf. A. 119, Mah. 210.

[83] A. 112, Mah. 204.

[84] Cf. p. 161.

Before, however, we consider the proof, it is necessary to refer
to a difficulty which seems to have escaped Kant altogether. The
preceding account of the synthesis involved in knowledge and in
self-consciousness implies, as his illustrations conclusively show,
that the synthesis requires a particular principle which constitutes
the individual manifold a whole of a particular kind.[85] But, if this
be the case, it is clear that the categories, which are merely
conceptions of an object in general, and are consequently quite
general, cannot possibly be sufficient for the purpose. And since the
manifold in itself includes no synthesis and therefore no principle of
synthesis, Kant fails to give any account of the source of the
particular principles of synthesis required for particular acts of
knowledge.[86] This difficulty--which admits of no solution--is
concealed from Kant in two ways. In the first place, when he describes
what really must be stated as the process by which parts or qualities
of an object become related to an object of a particular kind, he
thinks that he is describing a process by which representations become
related to an object in general.[87] Secondly, he thinks of the
understanding as the source of general principles of synthesis,
individual syntheses and the particul