In the first place, as has been said, Kant here introduces--and
introduces without warning--a totally new account of knowledge. It has
its origin in his theory of perception, according to which knowledge
begins with the production of sensations in us by things in
themselves. Since the spatial world which we come to know consists in
a multiplicity of related elements, it is clear that the isolated data
of sensation have somehow to be combined and unified, if we are to
have this world before us or, in other words, to know it. Moreover,
since these empirical data are subject to space and time as the forms
of perception, individual spaces and individual times, to which the
empirical data will be related, have also to be combined and unified.
On this view, the process of knowledge consists in combining certain
data into an individual whole and in unifying them through a principle
of combination.[6] If the data are empirical, the resulting knowledge
will be empirical; if the data are _a priori_, i. e. individual spaces
and individual times, the resulting knowledge will be _a priori_.[7]
This account of knowledge is new, because, although it treats
knowledge as a process or act of unifying a manifold, it describes a
different act of unification. As Kant first described the faculty of
judgement,[8] it unifies a group of particulars through relation to
the corresponding universal. As Formal Logic, according to Kant,
treats the faculty of judgement, it unifies two conceptions or two
prior judgements into a judgement. As Kant now describes the faculty
of judgement or thought, it unifies an empirical or an _a priori_
manifold of perception combined into an individual whole, through a
conception which constitutes a principle of unity. The difference
between this last account and the others is also shown by the fact
that while the first two kinds of unification are held to be due to
mere analysis of the material given to thought, the third kind of
unification is held to be superinduced by thought, and to be in no way
capable of being extracted from the material by analysis. Further,
this new account of knowledge does not replace the others, but is
placed side by side with them. For, according to Kant, there exist
_both_ the activity of thought which relates two conceptions in a
judgement,[9] _and_ the activity by which it introduces a unity of its
own into a manifold of perception. Nevertheless, this new account of
knowledge, or rather this account of a new kind of knowledge, must be
the important one; for it is only the process now described for the
first time which produces synthetic as opposed to analytic knowledge.
[6] Cf. A. 97, Mah. 193, 'Knowledge is a totality of compared
and connected representations.'