thout their
necessarily being related to functions of the understanding, and
therefore without the understanding containing _a priori_ the
conditions of these objects. Hence a difficulty appears here, which
we did not meet in the field of sensibility, viz. how _subjective
conditions of thought_ can have _objective validity_, i. e. can
furnish conditions of the possibility of all knowledge of objects;
for phenomena can certainly be given us in perception without the
functions of the understanding. Let us take, for example, the
conception of cause, which indicates a peculiar kind of synthesis in
which on A something entirely different B is placed[6] according to a
law. It is not _a priori_ clear why phenomena should contain something
of this kind ... and it is consequently doubtful _a priori_, whether
such a conception is not wholly empty, and without any corresponding
object among phenomena. For that objects of sensuous perception must
conform to the formal conditions of the sensibility which lie _a
priori_ in the mind is clear, since otherwise they would not be
objects for us; but that they must also conform to the conditions
which the understanding requires for the synthetical unity of thought
is a conclusion the cogency of which it is not so easy to see. For
phenomena might quite well be so constituted that the understanding
did not find them in conformity with the conditions of its unity, and
everything might lie in such confusion that, e. g. in the succession
of phenomena, nothing might present itself which would offer a rule of
synthesis, and so correspond to the conception of cause and effect, so
that this conception would be quite empty, null, and meaningless.
Phenomena would none the less present objects to our perception, for
perception does not in any way require the functions of thinking."[7]

[6] _Gesetzt._

[7] B. 121-3, M. 75-6.

This passage, if read in connexion with that immediately preceding
it,[8] may be paraphrased as follows: 'The argument of the _Aesthetic_
assumes the validity of mathematical judgements, which as such relate
to space and time, and thence it deduces the phenomenal character of
space and time, and of what is contained therein. At the same time the
possibility of questioning the validity of the law of causality, and
of similar principles, may lead us to question even the validity of
mathematical judgements. In the case of mathematical judgements,
however, in consequence o