Kant's Prolegomena to Any Future Metaphysics
Quote 1: My purpose is to persuade all those who think metaphysics worth studying that it is absolutely necessary to pause a moment and, regarding all that has been done as though undone, to propose first the preliminary question, "Whether such a thing as metaphysics be even possible at all?" (Page 3)
Quote 2: First, as concerns the sources of metaphysical knowledge, its very concept implies that they cannot be empirical. Its principles (including not only its maxims but its basic notions) must never be derived from experience à It is there a priori knowledge, coming from pure understanding and pure reason. (º1 Page 13)
Quote 3: [T]he generation of a priori knowledge by intuition as well as by concepts, in fine, of synthetic propositions a priori, especially in philosophical knowledge, constitutes the essential subject of metaphysics. (º2 Page 19)
Quote 4: [W]e find that all mathematical cognition has this peculiarity: it must first exhibit its concept in intuition and indeed a priori; therefore in an intuition which is not empirical but pure. (º7 Page 28)
Quote 5: My doctrine of the ideality of space and time [à] far from reducing the whole sensible world to mere illusion, is the only means of securing the application of one of the most important kinds of knowledge (that which mathematics propounds a priori) to actual objects and of preventing its being regarded as mere illusion. (º13 Page 39)
Quote 6: [A]s there is no intuition at all beyond the field of sensibility, these pure concepts, as they cannot possibly be exhibited in concreto, are void of all meaning; consequently all these noumena, together with their complex, the intelligible world, are nothing but representation of a problem, of which the object itself is possible but the solution, from the nature of our understanding, totally impossible. For our understanding is not a faculty of intuition, but of the c...