ernal perception[28] which
precedes[29] the objects themselves, and in which the conception of
them can be determined _a priori_? Obviously not otherwise than in so
far as it has its seat in the subject only, as the formal nature of
the subject to be affected by objects and thereby to obtain _immediate
representation_, i. e. _perception_ of them, and consequently only as
the form of the external sense in general."[30]

[28] 'External perception' can only mean perception of what
is spatial.

[29] _Vorhergeht._

[30] 'Formal nature _to be affected by objects_' is not
relevant to the context.

Here three steps are taken. From the _synthetic_ character of
geometrical judgements it is concluded that space is not something
which we _conceive_, but something which we _perceive_. From their _a
priori_ character, i. e. from the consciousness of necessity involved,
it is concluded that the perception of space must be _a priori_ in a
new sense, that of taking place _before_ the perception of objects in
it.[31] From the fact that we perceive space before we perceive
objects in it, and thereby are able to anticipate the spatial
relations which condition these objects, it is concluded that space is
only a characteristic of our perceiving nature, and consequently that
space is a property not of things in themselves, but only of things as
perceived by us.[32]

[31] Cf. B. 42, M. 26 (a) fin., (b) second sentence.

[32] Cf. B. 43, M. 26-7.

Two points in this argument are, even on the face of it, paradoxical.
Firstly, the term _a priori_, as applied not to geometrical judgements
but to the perception of space, is given a temporal sense; it means
not something whose validity is independent of experience and which is
the manifestation of the nature of the mind, but something which takes
place before experience. Secondly, the conclusion is not that the
perception of space _is the manifestation of_ the mind's perceiving
nature, but that it _is_ the mind's perceiving nature. For the
conclusion is that space[33] is the formal nature of the subject to be
affected by objects, and therefore the form of the external sense in
general. Plainly, then, Kant here confuses an actual perception and a
form or way of perceiving. These points, however, are more explicit in
the corresponding passage in the _Prolegomena_.[34]

[33] Kant draws no distinction between space and the
perception of space, or, rather, h