Since all the ways heretofore taken have failed to attain the goal,
and since without a preceding critique of pure reason it is not likely
ever to be attained, the present essay now before the public has a
fair title to an accurate and careful investigation, except it be
thought more advisable to give up all pretensions to metaphysics, to
which, if men but would consistently adhere to their purpose, no
objection can be made.
If we take the course of things as it is, not as it ought to be, there
are two sorts of judgments: (1) one a judgment which precedes
investigation (in our case one in which the reader from his own
metaphysics pronounces judgment on the Critique of Pure Reason which
was intended to discuss the very possibility of metaphysics); (2) the
other a judgment subsequent to investigation. In the latter the reader
is enabled to waive for awhile the consequences of the critical
researches that may be repugnant to his formerly adopted metaphysics,
and first examines the grounds whence those consequences are derived.
If what common metaphysics propounds were demonstrably certain, as for
instance the theorems of geometry, the former way of judging would
hold good. For if the consequences of certain principles are repugnant
to established truths, these principles are false and without further
inquiry to be repudiated. But if metaphysics does not possess a stock
of indisputably certain (synthetical) propositions, and should it even
be the case that there are a number of them, which, though among the
most specious, are by their consequences in mutual collision, and if
no sure criterion of the truth of peculiarly metaphysical
(synthetical) propositions is to be met with in it, then the former
way of judging is not admissible, but the investigation of the
principles of the critique must precede all judgments as to its value.