Luther 5
Experience tells us, indeed, what is, but not that it must necessarily be so, and not
otherwise. It therefore gives us no true universality; and reason, which is so insistent
upon this kind of knowledge, is therefore more stimulated by it than satisfied. Such
universal modes of knowledge, which at the same time possess the character of inner
necessity, must in themselves, independently of experience, be clear and certain. They
are therefore entitled knowledge a priori; whereas, on the other hand, that which is
borrowed solely from experience is, as we say, known only a posteriori, or empirically.
Now we find, what is especially noteworthy, that even into our experiences there enter
modes of knowledge which must have their origin a priori, and which perhaps serve only
to give coherence to our sense-representations. For if we eliminate from our experiences
everything which belongs to the senses, there still remain certain original concepts and
certain judgments derived from them, which must have arisen completely a priori,
independently of experience. . . .
21
Kant calls knowledge originating in experience a posteriori and knowledge that is
independent of all impressions of sense a priori. A priori principles, however, are
indispensable from the possibility of experience. Experience derives certainty from these
principles. Experience cannot give knowledge about necessary connections or about
universality of propositions. Thus, every succession of appearances lying in the object
itself and every objective change is only possible if it occurs according to a rule of cause
and effect. Kant claims that necessity and universality are sure criteria of a priori
knowledge, and he also sees mathematical propositions as proof of this necessity.
22
The
description of one’s experience refers to an ordered perspective on an independent world.
After establishing a priori knowledge, Kant endeavors to determine how such
knowledge is possible. He employs the distinction between analytic and synthetic
judgments to penetrate the essence of cognition. With his exploration of a priori
knowledge, he notes that among true propositions, some are true independently of
experience and remain true however experience varies—these are a priori truths. Other
propositions owe their truth to experience and might have been false if experience was
21
Kant, Critique of Pure Reason, p. 42.
22
Ibid., p. 44, says that “it is easy to show that there actually are in human knowledge judgments which are
necessary and in the strictest sense universal, and which are therefore pure a priori judgments. If an
example from the sciences be desired, we have only to look to any of the propositions of mathematics; if
we seek an example from the understanding in its quite ordinary employment, the proposition, ‘every
alteration must have a cause’ will serve our purpose.
Convention