If we thought to free ourselves from the labour of these investigations
by saying: “Experience is constantly offering us examples of the
relation of cause and effect in phenomena, and presents us with
abundant opportunity of abstracting the conception of cause, and so at
the same time of corroborating the objective validity of this
conception”; we should in this case be overlooking the fact, that the
conception of cause cannot arise in this way at all; that, on the
contrary, it must either have an à priori basis in the understanding,
or be rejected as a mere chimera. For this conception demands that
something, A, should be of such a nature that something else, B, should
follow from it necessarily, and according to an absolutely universal
law. We may certainly collect from phenomena a law, according to which
this or that usually happens, but the element of necessity is not to be
found in it. Hence it is evident that to the synthesis of cause and
effect belongs a dignity, which is utterly wanting in any empirical
synthesis; for it is no mere mechanical synthesis, by means of
addition, but a dynamical one; that is to say, the effect is not to be
cogitated as merely annexed to the cause, but as posited by and through
the cause, and resulting from it. The strict universality of this law
never can be a characteristic of empirical laws, which obtain through
induction only a comparative universality, that is, an extended range
of practical application. But the pure conceptions of the understanding
would entirely lose all their peculiar character, if we treated them
merely as the productions of experience.
Transition to the Transcendental Deduction of the Categories § 10