| No one, therefore, can admit the validity of the use of such rules as first principles. |
| But, for the present, we may content ourselves with having established the fact, that we do possess and exercise a faculty of pure a priori cognition; and, secondly, with having pointed out the proper tests of such cognition, namely, universality and necessity. |
| Not only in judgements, however, but even in conceptions, is an a priori origin manifest. |
| For example, if we take away by degrees from our conceptions of a body all that can be referred to mere sensuous experience--colour, hardness or softness, weight, even impenetrability--the body will then vanish; but the space which it occupied still remains, and this it is utterly impossible to annihilate in thought. |
| Again, if we take away, in like manner, from our empirical conception of any object, corporeal or incorporeal, all properties which mere experience has taught us to connect with it, still we cannot think away those through which we cogitate it as substance, or adhering to substance, although our conception of substance is more determined than that of an object. |
| Compelled, therefore, by that necessity with which the conception of substance forces itself upon us, we must confess that it has its seat in our faculty of cognition a priorI. |
| III. Philosophy stands in need of a Science which shall Determine the Possibility, Principles, and Extent of Human Knowledge "a priori" |
| Of far more importance than all that has been above said, is the consideration that certain of our cognitions rise completely above the sphere of all possible experience, and by means of conceptions, to which there exists in the whole extent of experience no corresponding object, seem to extend the range of our judgements beyond its bounds. |
| And just in this transcendental or supersensible sphere, where experience affords us neither instruction nor guidance, lie the investigations of reason, which, on account of their importance, we consider far preferable to, and as having a far more elevated aim than, all that the understanding can achieve within the sphere of sensuous phenomena. |
| So high a value do we set upon these investigations, that even at the risk of error, we persist in following them out, and permit neither doubt nor disregard nor indifference to restrain us from the pursuit. |
| These unavoidable problems of mere pure reason are God, freedom (of will), and immortality. |
| The science which, with all its preliminaries, has for its especial object the solution of these problems is named metaphysics--a science which is at the very outset dogmatical, that is, it confidently takes upon itself the execution of this task without any previous investigation of the ability or inability of reason for such an undertaking. |
| Now the safe ground of experience being thus abandoned, it seems nevertheless natural that we should hesitate to erect a building with the cognitions we possess, without knowing whence they come, and on the strength of principles, the origin of which is undiscovered. |
| Instead of thus trying to build without a foundation, it is rather to be expected that we should long ago have put the question, how the understanding can arrive at these a priori cognitions, and what is the extent, validity, and worth which they may possess? |
| We say, "This is natural enough," meaning by the word natural, that which is consistent with a just and reasonable way of thinking; but if we understand by the term, that. |
| which usually happens, nothing indeed could be more natural and more comprehensible than that this investigation should be left long unattempted. |
| For one part of our pure knowledge, the science of mathematics, has been long firmly established, and thus leads us to form flattering expectations with regard to others, though these may be of quite a different nature. |
| Besides, when we get beyond the bounds of experience, we are of course safe from opposition in that quarter; and the charm of widening the range of our knowledge is so great that, unless we are brought to a standstill by some evident contradiction, we hurry on undoubtingly in our course. |
| This, however, may be avoided, if we are sufficiently cautious in the construction of our fictions, which are not the less fictions on that account. |
| Mathematical science affords us a brilliant example, how far, independently of all experience, we may carry our a priori knowledge. |
| It is true that the mathematician occupies himself with objects and cognitions only in so far as they can be represented by means of intuition. |