PROLEGOMENA TOANYFUTUREMETAPHYSICS 809
which we distinguish judgments of experience from those of perception. This takes
place because appearances, as mere intuitions occupying a part of space and time,come
under the concept of quantity, which synthetically unites their multiplicity a priori
according to rules. Again, insofar as the perception contains, besides intuition, sensa-
tion, and between the latter and nothing (that is, the total disappearance of sensation),
there is an ever-decreasing transition, it is apparent that the real within appearances
must have a degree, so far as it (namely, the sensation) does not itself occupy any part of
space or of time.* Still the transition to this real from empty time or empty space is
possible only in time. Consequently, although sensation, as the quality of empirical
intuition specifically differentiating it from other sensations, can never be known a priori,
yet it can, in a possible experience in general, as quantity of perception be intensively
distinguished from every other similar perception. Hence the application of mathemat-
ics to nature, as regards the sensuous intuition by which nature is given to us, thus
becomes possible and definite.
Above all, the reader must pay attention to the mode of proof of the principles
which occur under the title of “analogies of experience.” For these do not refer to the
genesis of intuitions, as do the principles of applying mathematics to natural science in
general, but to the connection of their existence in an experience; and this can be nothing
but the determination of their existence in time according to necessary laws, under which
alone the connection is objectively valid and thus becomes experience. The proof, there-
fore, does not turn on the synthetical unity in the connection of things in themselves, but
merely of perceptions; and of these, not in regard to their matter, but to the determination
of time and of the relation of their existence in it according to universal laws. If the
empirical determination in relative time is indeed to be objectively valid (that is, to be
experience), these universal laws must contain the necessary determination of existence
in time generally (namely, according to a rule of the understanding a priori).
As these are prolegomena I cannot here further descant on the subject, but my
reader (who has probably been long accustomed to consider experience a mere
empirical synthesis of perceptions, and hence has not considered that it goes much
beyond them since it imparts to empirical judgments universal validity, and for that
purpose requires a pure and a prioriunity of the understanding) is recommended to
pay special attention to this distinction of experience from a mere aggregate of
perceptions and to judge the mode of proof from this point of view.
§ 27. Now we are prepared to remove Hume’s doubt. He justly maintains that we
cannot comprehend by reason the possibility of causality, that is, of the reference of the
existence of one thing to the existence of another which is necessitated by the former. I
add that we comprehend just as little the concept of subsistence, that is, the necessity that
at the foundation of the existence of things there lies a subject which cannot itself be a
predicate of any other thing; nay, we cannot even form a notion of the possibility of such
a thing (though we can point out examples of its use in experience). The very same incom-
prehensibility affects the community of things, as we cannot comprehend how from the310*Heat and light are in a small space just as large, as to degree, as in a large one; in like manner the
internal representations, pain, consciousness generally, whether they last a short or a long time, need not vary
as to the degree. Hence the quantity is here in a point and in a moment just as great as in any space or time,
however great. Degrees are quantities not in intuition, but in mere sensation (or the quantity of the content
[Grundes] of an intuition). Hence they can only be estimated quantitatively by the relation of 1 to 0, namely,
by their capability of decreasing by infinite intermediate degrees to disappearance, or of increasing from
naught through infinite gradations to a determinate sensation in a certain time. Quantitas qualitatis est
gradus.“The quantity of quality is degree.”