contradiction, and which you believe you conceive quite
independently of all experience; how do you arrive at this, and
how will you justify your pretensions? An appeal to the consent
of the common sense of mankind cannot be allowed; for that is a
witness whose authority depends merely upon rumor. Says Horace:

     " Quodcunque ostendis mihi sic, incredulus odi."
     "To all that which thou provest me thus, I refuse to give
     credence. "

     The answer to this question, though indispensable, is
difficult; and though the principal reason that it was not made
long ago is, that the possibility of the question never occurred
to anybody, there is yet another reason, which is this that a
satisfactory answer to this one question requires a much more
persistent, profound, and painstaking reflection, than the most
diffuse work on Metaphysics, which on its first appearance
promised immortality to its author. And every intelligent reader,
when he carefully reflects what this problem requires, must at
first be struck with its difficulty, and would regard it as
insoluble and even impossible, did there not actually exist pure
synthetical cognitions a priori. This actually happened to David
Hume, though he did not conceive the question in its entire
universality as is done here, and as must be done, should the
answer be decisive for all Metaphysics. For how is it possible,
says that acute man, that when a concept is given me, I can go
beyond it and connect with it another, which is not contained in
it, in such a manner as if the latter necessarily belonged to the
former? Nothing but experience can furnish us with such
connections (thus he concluded from the difficulty which he took
to be an impossibility), and all that vaunted necessity, or, what
is the same thing, all cognition assumed to be a priori, is
nothing but a long habit of accepting something as true, and
hence of mistaking subjective necessity for objective.

     Should my reader complain of the difficulty and the trouble
which I occasion him in the solution of this problem, he is at
liberty to solve it himself in an easier way. Perhaps he will
then feel under obligation to the person who has undertaken for
him a labor of so profound research, and will rather be surprised
at the facility with which, considering the nature of the
subject, the solution has been attained. Yet it has cost years of
work to solve the problem in its whole universality (using the
term in the mathematical sense, viz., for that which is
sufficient for all cases), and finally to exhibit it in the
analytical form, as the reader finds it here.

     All metaphysicians are therefore solemnly and legally
suspended from their occupations till they shall have answered in
a satisfactory manner the question, "How are synthetic cognitions
a priori possible?" For the answer contains the only credentials
which they must show when they have anything to offer in the name
of pure reason. But if they do not possess these credentials,
they can expect nothing else of reasonable people, who have been
deceived so often, than to be dismissed without further ado.

     If they on the other hand desire to carry on their business,
not as a science, but as an art of wholesome oratory suited to
the common sense of man, they cannot in justice be prevented.
They will then speak the modest language of a rational belief,
they will grant that they are not allowed even to conjecture, far
less to know, anything which lies beyond the bounds of all
possible experience, but only to assume (not for speculative use,
which they must abandon, but for practical purposes only) the
existence of something that is possible and even indispensable
for the guidance of the understanding and of the will in life. In
this mariner alone can they be called useful and wise men, and
the more so as they renounce the title of metaphysicians; for the
latter profess to be speculative philosophers, and since, when
judgments a prior: are under discussion, poor probabilities
cannot be admitted (for what is declared to be known a priori is
thereby announced as necessary), such men cannot be permitted to
play with conjectures, but their assertions must be either
science, or are worth nothing at all.

     It may be said, that the entire transcendental philosophy,
which necessarily precedes all metaphysics, is nothing but the
complete solution of the problem here propounded, in systematical
order and completeness, and hitherto we have never had any
transcendental philosophy; for what goes by its name is properly
a part of metaphysics, whereas the former sciences intended first
to constitute the possibility of the 'matter, and must therefore
precede all metaphysics. And it is not surprising that when a
whole science, deprived of all help from other sciences, and
consequently in itself quite new, is required to answer a -single
question satisfactorily, we should find the answer troublesome
and difficult, nay even shrouded in obscurity.

     As we now proceed to this solution according to the
analytical method, in which we assume that such cognitions from
pure reasons actually exist, we can only appeal to two sciences
of theoretical cognition . which alone is under consideration
here), pure mathematics and pure natural science (physics). For
these alone can exhibit to us objects in a definite and
actualizable form (in der Anschauung), and consequently (if there
should occur in them a cognition a priori) can show the truth or
conformity of the cognition to the object in concrete, that is,
its actuality, from which we could proceed to the reason of its
possibility by the analytic method. This facilitates our work
greatly for here universal considerations are not only applied to