The identity of the will and the body, of which we have now given a cursory explanation, can only be proved in the manner we have adopted here. We have proved this identity for the first time, and shall do so more and more fully in the course of this work. By “proved” we mean raised from the immediate consciousness, from knowledge in the concrete to abstract knowledge of the reason, or carried over into abstract knowledge. On the other hand, from its very nature it can never be demonstrated, that is, deduced as indirect knowledge from some other more direct knowledge, just because it is itself the most direct knowledge; and if we do not apprehend it and stick to it as such, we shall expect in vain to receive it again in some indirect way as derivative knowledge. It is knowledge of quite a special kind, whose truth cannot therefore properly be brought under any of the four rubrics under which I have classified all truth in the essay on the principle of sufficient reason, § 29, the logical, the empirical, the metaphysical, and the metalogical, for it is not, like all these, the relation of an abstract idea to another idea, or to the necessary form of perceptive or of abstract ideation, but it is the relation of a judgment to the connection which an idea of perception, the body, has to that which is not an idea at all, but something _toto genere_ different, will. I should like therefore to distinguish this from all other truth, and call it κατ᾽ εξοχην _philosophical truth_. We can turn the expression of this truth in different ways and say: My body and my will are one;—or, What as an idea of perception I call my body, I call my will, so far as I am conscious of it in an entirely different way which cannot be compared to any other;—or, My body is the _objectivity_ of my will;—or, My body considered apart from the fact that it is my idea is still my will, and so forth.(27) § 19. In the first book we were reluctantly driven to explain the human body as merely idea of the subject which knows it, like all the other objects of this world of perception. But it has now become clear that what enables us consciously to distinguish our own body from all other objects which in other respects are precisely the same, is that our body appears in consciousness in quite another way _toto genere_ different from idea, and this we denote by the word _will_; and that it is just this double knowledge which we have of our own body that affords us information about it, about its action and movement following on motives, and also about what it experiences by means of external impressions; in a word, about what it is, not as idea, but as more than idea; that is to say, what it is _in itself_. None of this information have we got directly with regard to the nature, action, and experience of other real objects.