The perception of a body in space is a very complicated process. I see suddenly before me, for example, a white ball. This has the effect of conveying to me more than a mere sensation of whiteness. I deduce the spherical character of the ball from the gradations of light and shade upon its surface. I form a correct appreciation of its distance from my eye, and hence again I deduce an inference as to the size of the ball. What an expenditure of sensations, ideas, and inferences is found to be necessary before all this can be brought about; yet the production of a correct perception of the ball was the work only of a few seconds, and I was unconscious of the individual processes by means of which it was effected, the result as a whole being alone present in my consciousness. The nerve substance preserves faithfully the memory of habitual actions. {72} Perceptions which were once long and difficult, requiring constant and conscious attention, come to reproduce themselves in transient and abridged guise, without such duration and intensity that each link has to pass over the threshold of our consciousness. We have chains of material nerve processes to which eventually a link becomes attached that is attended with conscious perception. This is sufficiently established from the standpoint of the physiologist, and is also proved by our unconsciousness of many whole series of ideas and of the inferences we draw from them. If the soul is not to ship through the fingers of physiology, she must hold fast to the considerations suggested by our unconscious states. As far, however, as the investigations of the pure physicist are concerned, the unconscious and matter are one and the same thing, and the physiology of the unconscious is no “philosophy of the unconscious.” By far the greater number of our movements are the result of long and arduous practice. The harmonious cooperation of the separate muscles, the finely adjusted measure of participation which each contributes to the working of the whole, must, as a rule, have been laboriously acquired, in respect of most of the movements that are necessary in order to effect it. How long does it not take each note to find its way from the eyes to the fingers of one who is beginning to learn the pianoforte; and, on the other hand, what an astonishing performance is the playing of the professional pianist. The sight of each note occasions the corresponding movement of the fingers with the speed of thought—a hurried glance at the page of music before him suffices to give rise to a whole series of harmonies; nay, when a melody has been long practised, it can be played even while the player’s attention is being given to something of a perfectly different character over and above his music.