And such stuff as this is gravely taught fifty years after Kant's death! The aim of it is, as we know, to undermine Kantian philosophy, and certainly if these propositions were true, _one_ stroke would suffice to overthrow it. Fortunately however these assertions are of a kind which is met by derision rather than by serious refutation. For, in them, the question is one of heresy, not so much against Kantian philosophy, as against common sense; and they are not so much an attack upon any particular philosophical dogma, as upon an _à priori_ truth which, as such, constitutes human understanding itself, and therefore must be instantaneously evident to every one who is in his senses, just as much as that 2 × 2 = 4. Fetch me a peasant from the plough; make the question intelligible to him; and he will tell you, that even if all things in Heaven and on Earth were to vanish, Space would nevertheless remain, and that if all changes in Heaven and on Earth were to cease, Time would nevertheless flow on. Compared with German pseudo-philosophers like these, how estimable does a man like the French physicist Pouillet appear, who, though he never troubles his head about Metaphysics, is careful to incorporate two long paragraphs, one on _l'Espace_, the other on _le Temps_, in the first chapter of his well-known Manual, on which public instruction in France is based, where he shows that if all Matter were annihilated, Space would still remain, and that Space is infinite; and that if all changes ceased, Time would still pursue its course without end. Now here he does not appeal, as in all other cases, to experience, because in this case experience is not possible; yet he speaks with apodeictic certainty. For, as a physicist, professing a science which is absolutely immanent--_i.e._ limited to the reality that is empirically given--it never comes into his head to inquire whence he knows all this. It _did_ come into Kant's head, and it was this very problem, clothed by him in the severe form of an inquiry as to the possibility of synthetical _à priori_ judgments, that became the starting-point and the corner-stone of his immortal discoveries, or in other words, of Transcendental Philosophy which, precisely by answering this question and others related to it, shows what is the nature of that empirical reality itself.[176]