We will assume for the moment that we know nothing of theories of matter and theories of spirit, nothing of the discussions as to the reality or ideality of the external world. Here I am in the presence of images, in the vaguest sense of the word, images perceived when my senses are opened to them, unperceived when they are closed. All these images act and react upon one another in all their elementary parts according to constant laws which I call laws of nature, and, as a perfect knowledge of these laws would probably allow us to calculate and to foresee what will happen in each of these images, the future of the images must be contained in their present and will add to them nothing new.
Yet there is one of them which is distinct from all the others, in that I do not know it only from withoutThe unique place and function of the living body. by perceptions, but from within by affections: it is my body. I examine the conditions in which these affections are produced: I find that they always interpose themselves between the excitations that I receive from without and the move-
1
