The manner in which Kant thus departs from the strict application of the
synthetic method may be illustrated by an analysis of his argument in
the _Aesthetic_.[182] Only in the arguments of the first edition in
regard to space and time is the synthetic method employed in its ideal
and rigorous form. For the most part, even in the first edition, instead
of showing how the _a priori_ character of pure and applied mathematics
follows from conclusions independently established, he assumes both pure
and applied mathematics to be given as valid, and seeks only to show how
the independently established results of the _Aesthetic_ enable him to
explain and render comprehensible their recognised characteristics. This
is not, indeed, any very essential modification of the synthetic method;
for his independently established results suffice for deducing all that
they are used to explain. The validity of mathematics is not employed as
a premiss. Kant’s argument is, however, made less clear by the above
procedure.
Further difficulty is caused by Kant’s occasional employment, even in
the first edition, of the analytic method. He several times cites as an
argument in support of his view of space the fact that it alone will
account for the existing science of geometry. That is to say, he employs
geometry, viewed as valid, to _prove_ the correctness of his view of
space.[183] Starting from that science as given, he enquires what are
the conditions which can alone render it possible. These conditions are
found to coincide with those independently established. Now this is a
valid argument when employed in due subordination to the main synthetic
method. It offers welcome _confirmation_ of the results of that method.
It amounts in fact to this, that having proved (by application of the
transcendental method) the mathematical sciences to be valid, everything
which their validity necessarily implies must be granted. Kant’s
reasoning here becomes circular, but it is none the less valid on that
account. This further complication of the argument is, however,
dangerously apt to mislead the reader. It is in great part the cause of
the above division among Kant’s commentators. The method employed in the
_Prolegomena_ is simply this form of argument systematised and cut free
from all dependence upon the transcendental method of proof.[184]