a combination of the manifold as renders
possible a thoroughgoing synthesis of reproduction, then this
synthesis of imagination is based, even before all experience, on _a
priori_ principles, and we must assume a pure transcendental synthesis
of the imagination which lies at the foundation of the very
possibility of all experience (as that which necessarily presupposes
the reproducibility of phenomena)."[23]

[23] A. 100-2, Mah. 195-7.

In other words, the faculty of reproduction, if it is to get to work,
presupposes that the elements of the manifold are parts of a
necessarily related whole; or, as Kant expresses it later, it
presupposes the _affinity_ of phenomena; and this affinity in turn
presupposes that the synthesis of apprehension by combining the
elements of the manifold on certain principles makes them parts of a
necessarily related whole.[24]

[24] Cf. A. 113, Mah. 205; A. 121-2, Mah. 211-12; and Caird,
i. 362-3. For a fuller account of these presuppositions, and
for a criticism of them, cf. Ch. IX, p. 219 and ff.

3. Kant introduces the third operation, which he calls 'the synthesis
of recognition in the conception',[25] as follows:

[25] This title also is a misnomer due to the desire to give
parallel titles to the three operations involved in
knowledge. There is really only one synthesis referred to,
and the title here should be 'the recognition of the
synthesis in the conception'.

"Without consciousness that what we are thinking is identical with
what we thought a moment ago, all reproduction in the series of
representations would be in vain. For what we are thinking would be a
new representation at the present moment, which did not at all belong
to the act by which it was bound to have been gradually produced, and
the manifold of the same would never constitute a whole, as lacking
the unity which only consciousness can give it. If in counting I
forget that the units which now hover before my mind have been
gradually added by me to one another, I should not know the generation
of the group through this successive addition of one to one, and
consequently I should not know the number, for this conception
consists solely in the consciousness of this unity of the synthesis."

"The word 'conception'[26] might itself lead us to this remark. For
it is this _one_ consciousness which unites the manifold gradually
perceived and then also reproduced into one representatio