reality as it is in itself, but of reality as it is for us. Accept this explanation, and our difficulties begin to disappear. For, as forms of human perception, space and time are for us unalterable. Since they belong to the very constitution of our minds, we can apprehend no object of sense without giving it the form under which such apprehension is alone possible for us. Leibnitz was therefore mistaken in supposing that space and time are merely confused conceptions of the mutual relations of things; were that true, we should be capable of grasping individual realities by analyzing our first conceptions of things until we had made them perfectly clear. The truth is that space and time are not conceptions at all, but perceptions, and hence no precision of analysis can get rid of them. We are unable even to conceive the possibility of a knowledge that does not conform to the conditions of space and time; for, as has been said, no definite object can be apprehended except under those conditions.
The peculiar doctrine of Kant in regard to the nature of space and time is thus interwoven with his whole system of thought. In one form or other he is always occupied with the opposition of objects of sensible experience, which can never be ultimate realities because they can never be complete individuals, and the inextinguishable impulse to believe in and to seek for such realities. But before dealing formally with the contrast of phenomenal and noumenal, he seeks to provide a firm basis for the mathematical and physical sciences. Though the forms of our perception do not admit of a knowledge of the real in its ultimate nature, yet certain fundamental principles of scientific knowledge can be rigidly demonstrated. The first of these principles is, that every object of sensible experience that we ever have known, or ever can know, is an extensive quantum. This conclusion follows from the necessary and normal operation of our minds under conditions of space and time. For we cannot apprehend any sensible object without picturing it as spread out in space, or as a succession in time. Even the pure magnitudes of mathematics—such as a line, or a day—must be so presented. Eliminate space and time, and
