Here, as in the preface to the first edition, the problem of the Critique is declared to be the explanation of a priori knowledge, that is, a rational knowledge of objects prior to experience of them. But, it is here added, the fact of such knowledge impels us to make the Copernican assumption, that objects must conform to our mode of cognition. There is no difficulty in applying the assumption to the objects of sensuous perception (Anschauung), as Kant made clear in the Dissertation of 1770. If the perception had to conform to the constitution of objects, how could we know anything a priori about these objects? But if the object (as an object of the senses, not of reason) conform to the constitution of our faculty of sense-perception, we may easily have a priori knowledge of it. Still we cannot stop at these sense-presentations, if they are to become knowledge. Perceptions without thought are blind. They must be referred, as representations, to something as their object, which we endeavor to determine through them. This object then must be conceived. And I have the choice of admitting either that the concepts by which I determine it conform to the object, in which case it is impossible to see how I can know anything about it a priori; or that the objects, or what is the same, the experience in which alone they are known, must conform to those concepts, in which case the problem of a priori knowledge is again solved. For experience, as a kind of knowledge, requires understanding; and the rules by which understanding acts must be considered logically prior to the objects given through them. These rules, existing in me a priori, are expressible in a priori concepts, to which accordingly all objects of experience must necessarily conform. In general terms, Kant's revolutionary metaphysical thought is "that we can know a priori of things only that which we ourselves put into them."[1] And from this it follows that such a priori knowledge can never be of things as they
- ↑ III, 19 (I, 372). Similarly Leibnitz, Nouveaux Essais, p. 195 A (Erdmann's ed.) or V. 42-3 (Gerhardt's ed.): Si quelques évènemens peuvent être prévûs avant toute épreuve qu'on en ait faite, il est manifeste, que nous y contribuons quelque chose de notre part.
