analytical judgments, but wherein the procedure is not different
from that in every other kind of knowledge, in which we merely
seek to render our concepts distinct by analysis. But the
generation of a priori cognition by concrete images as well as by
concepts, in fine of synthetical propositions a priori in
philosophical cognition, constitutes the essential subject of
Metaphysics.

     Weary therefore as well of dogmatism, which teaches us
nothing, as of skepticism, which does not even promise us
anything, not even the quiet state of a contented ignorance;
disquieted by the importance of knowledge so much needed; and
lastly, rendered suspicious by long experience of all knowledge
which we believe we possess, or which offers itself, under the
title of pure reason: there remains but one critical question on
the answer to which our future procedure depends, viz., Is
Metaphysics at all possible? But this question must be answered
not by skeptical objections to the asseverations of some actual
system of metaphysics (for we do not as yet admit such a thing to
exist), but from the conception, as yet only problematical, of a
science of this sort.

     In the Critique of Pure Reason I have treated this question
synthetically, by making inquiries into pure reason itself, and
endeavoring in this source to determine the elements as well as
the laws of its pure use according to principles. The task is
difficult, and requires a resolute reader to penetrate by degrees
into a system, based on no data except reason itself, and which
therefore seeks, without resting upon any fact, to unfold
knowledge from its original germs. Prolegomena, however, are
designed for preparatory exercises; they are intended rather to
point out what we have to do in order if possible to actualize a
science, than to propound it. They must therefore rest upon
something already known as trustworthy, from which we can set out
with confidence, and ascend to sources as yet unknown, the
discovery of which will not only explain to us what we knew, but
exhibit a sphere of many cognitions which all spring from the
same sources. The method of Prolegomena, especially of those
designed as a preparation for future metaphysics, is consequently
analytical.

     But it happens fortunately, that though we cannot assume
metaphysics to be an actual science, we can say with confidence
that certain pure a priori synthetical cognitions, pure
Mathematics and pure Physics are actual and given; for both
contain propositions, which are thoroughly recognized as
apodictically certain, partly by mere reason, partly by general
consent arising from experience, and yet as independent of
experience. We have therefore some at least uncontested
synthetical knowledge a priori, and need not ask whether it be
possible, for it is actual, but how it is possible, in order that
we may deduce from the principle which makes the given cognitions
possible the possibility of all the rest.

 Sect. 5. The General Problem: How is Cognition from Pure Reason
                            Possible?

     We have above learned the significant distinction between
analytical and synthetical judgments. The possibility of
analytical propositions was easily comprehended, being entirely
founded on the law of Contradiction. The possibility of
synthetical a posteriori judgments, of those which are gathered
from experience, also requires no particular explanation; for
experience is nothing but a continual synthesis of perceptions.
There remain therefore only synthetical propositions a priori, of
which the possibility must be sought or investigated, because
they must depend upon other principles than the law of
contradiction.

     But here we need not first establish the possibility of such
propositions so as to ask whether they are possible. For there
are enough of them which indeed are of undoubted certainty, and
as our present method is analytical, we shall start from the
fact, that such synthetical but purely rational cognition
actually exists; but we must now inquire into the reason of this
possibility, and ask, how such cognition is possible, in order
that we may from the principles of its possibility be enabled to
determine the conditions of its use, its sphere and its limits.
The proper problem upon which all depends, when expressed with
scholastic precision, is therefore: How are Synthethetic
Propositions a priori possible?

     For the sake of popularity I have above expressed this
problem somewhat differently, as an inquiry into purely rational
cognition, which I could do for once without detriment to the
desired comprehension, because, as we have only to do here with
metaphysics and its sources, the reader will, I hope, after the
foregoing remarks, keep in mind that when we speak of purely
rational cognition, we do not mean analytical, but synthetical
cognition.6

     Metaphysics stands or falls with the solution of this
problem: its very existence depends upon it. Let any one make
metaphysical assertions with ever so much plausibility, let him
overwhelm us with conclusions, if he has not previously proved
able to answer this question satisfactorily, I have a right to
say this is all vain baseless philosophy and false wisdom. You
speak through pure reason, and claim, as it were to create
cognitions a priori. by not only dissecting given concepts, but
also by asserting connections which do not rest upon the law of