If I remember my last year's perception, I do not dig it out from an under-mind, in which it was stored up and buried, but I create an entirely new memory picture, just as I may make to-day a speech which says the same thing which I said last year, and yet my action of speaking is not last year's speech movement. It is a new action, and the movement did not lie over somewhere during the interval. Mental life is produced anew in every moment. When the first experience is gone and the second comes, nothing of the stuff from which the first was made still has existence in the content of consciousness. By this fact it becomes entirely impossible ever to conceive necessary connections in the sense of physical necessity in the world of consciousness. The one idea may bring to me another idea by association, but as long as I consider both strictly as mental facts, I can never understand why this association happens, I can never grasp the real mechanism of the connection, I can never see necessity between the disappearance of the one and the appearance of the other. It remains a mystery which does not justify any expectation that the same sequence will result again. Whatever belongs to the psychical world can never be linked by a real insight into necessity. Causality there remains an empty name without promise of a real explanation. Only when we have recognized this fundamental difficulty in the efforts for psychological explanation, can we understand the way which modern psychology has taken most successfully. The end of this way is simply this: every psychical fact is to be thought of as an accompaniment of a physical process and the necessary connections of these physical processes determine, then, the connections of the mental facts. Indeed this has become the method of modern psychology. It has brought about the intimate relation between psychology and the physiology of the brain, and has given us, as foundation, the theory of psychophysical parallelism; the theory that there is no psychical process without a parallel brain process. But the real center of the theory lies indeed in the fact which we discussed; it lies in the fact that we cannot have any explanation of mental states as such at all, if we do not link them with physical processes.