memories which aspire to fill themselves with color, with sonority, in short with materiality, the only ones that succeed are those which can assimilate themselves with the color-dust that we perceive, the external and internal sensations that we catch, etc., and which, besides, respond to the affective tone of our general sensibility.[1] When this union is effected between the memory and the sensation, we have a dream. In a poetic page of the Enneades, the philosopher Plotinus, interpreter and continuator of Plato, explains to us how men come to life. Nature, he says, sketches the living bodies, but sketches them only. Left to her own forces she can never complete the task. On the other hand, souls inhabit the world of Ideas. Incapable in themselves of acting, not even thinking of action, they float beyond space and beyond time. But, among all the bodies, there are some which specially respond by their form to the aspirations of some particular souls; and among these souls there are those which recognize themselves in some particular body. The body, which does not come altogether viable from the hand of nature, rises toward the soul which might give it complete life; and the soul, looking upon the body and believing that it perceives its own image as in a mirror, and attracted, fascinated by the image, lets itself fall. It falls, and this fall is life. I may compare to these detached souls the memories plunged in the obscurity of the unconscious. On the other hand, our nocturnal sensations resemble these incomplete bodies. The sensation is warm, colored, vibrant and almost living, but vague. The memory is complete, but airy and lifeless. The sensation wishes to find a form on which to mold the vagueness of its contours. The memory would obtain matter to fill it, to ballast it, in short to realize it. They are drawn toward each other; and the phantom memory, incarnated in the sensation which brings to it flesh and blood, becomes a being with a life of its own, a dream.