810 IMMANUELKANT
state of one thing an inference to the state of quite another thing beyond it, and vice versa,
can be drawn, and how substances which have each their own separate existence should
depend upon one another necessarily. But I am very far from holding these concepts to be
derived merely from experience, and the necessity represented in them to be imaginary
and a mere illusion produced in us by long habit. On the contrary, I have amply shown that
they and the principles derived from them are firmly established a prioribefore all expe-
rience and have their undoubted objective value, though only with regard to experience.
§ 28. Although I have no notion of such a connection of things in themselves, how
they can either exist as substances, or act as causes, or stand in community with others (as
parts of a real whole), and I can just as little conceive such properties in appearances as
such (because those concepts contain nothing that lies in the appearances, but only what
the understanding alone must think), we have yet a concept of such a connection of repre-
sentations in our understanding and in judgments generally. This concept is: that repre-
sentations appear, in one sort of judgments, as subject in relation to predicates; in another,
as ground in relation to consequent; and, in a third, as parts which constitute together a
total possible cognition. Furthermore, we know a priorithat without considering the rep-
resentation of an object as determined in one or the other of these respects, we can have no
valid knowledge of the object; and, if we should occupy ourselves about the object in
itself, there is not a single possible attribute by which I could know that it is determined
under any of these aspects, that is, under the concept either of substance, or of cause, or (in
relation to other substances) of community, for I have no concept of the possibility of such
a connection of existence. But the question is not how things in themselves but how the
empirical knowledge of things is determined, as regards the above aspects of judgments in
general; that is, how things, as objects of experience, can and must be subsumed under
these concepts of the understanding. And then it is clear that I completely comprehend,
not only the possibility, but also the necessity, of subsuming all appearances under these
concepts—that is, of using them for principles of the possibility of experience.
§ 29. In order to test Hume’s problematical concept (his crux metaphysicorum),
the concept of cause, we are first given a priori,by means of logic, the form of a condi-
tional judgment in general; that is, we have one cognition given as antecedent and
another as consequent. But it is possible that in perception we may meet with a rule of
relation which runs thus: that a certain appearance is constantly followed by another
(though not conversely); and this is a case for me to use the hypothetical judgment and,
for instance, to say if the sun shines long enough upon a body it grows warm. Here there
is indeed as yet no necessity of connection or concept of cause. But I proceed and say
that, if this proposition, which is merely a subjective connection of perceptions, is to be
a proposition of experience, it must be seen as necessary and universally valid. Such a
proposition would be that the sun is by its light the cause of heat. The empirical rule is
now considered as a law, and as valid, not merely of appearances but valid of them for
the purposes of a possible experience which requires universal and therefore necessarily
valid rules. I therefore easily comprehend the concept of cause, as a concept necessarily
belonging to the mere form of experience, and its possibility as a synthetical union of
perceptions in consciousness in general; but I do not at all comprehend the possibility of
a thing in general as a cause, because the concept of cause denotes a condition not at all
belonging to things, but to experience. For experience can be nothing but objectively
valid knowledge of appearances and of their succession, only so far as the earlier can be
conjoined with the later according to the rule of hypothetical judgments.
§ 30. Hence if even the pure concepts of the understanding are thought to go beyond
objects of experience to things in themselves (noumena), they have no meaning whatever.311
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