First of all, there are reservations to be made in regard to the very principle which is at the basis of this theory. It is taken for granted that the soul is entirely distinct from the body, that it is its double, and that within it or outside of it, it normally lives its own autonomous life. Now we shall see[107] that this conception is not that of the primitive, or at least, that it only expresses one aspect of his idea of the soul. For him, the soul, though being under certain conditions independent of the organism which it animates, confounds itself with this latter to such an extent that it cannot be radically separated from it: there are organs which are not only its appointed seat, but also its outward form and material manifestation. The notion is therefore more complex than the doctrine supposes, and it is doubtful consequently whether the experiences mentioned are sufficient to account for it; for even if they did enable us to understand how men have come to believe themselves double, they cannot explain how this duality does not exclude, but rather, implies a deeper unity and an intimate interpenetration of the two beings thus differentiated. But let us admit that the idea of the soul can be reduced to the idea of a double, and then see how this latter came to be formed. It could not have been suggested to men except by the experience of dreams. That they might understand how they could see places more or less distant during sleep, while their bodies remained lying on the ground, it would seem that they were led to conceive of themselves as two beings: on the one hand, the body, and on the other, a second self, able to leave the organism in which it lives and to roam about in space. But if this hypothesis of a double is to be able to impose itself upon men with a sort of necessity, it should be the only one possible, or at least, the most economical one. Now as a matter of fact, there are more simple ones which, it would seem, might have occurred to the mind just as naturally. For example, why should the sleeper not imagine that while asleep he is able to see things at a distance? To imagine such a power would demand less expense to the imagination than the construction of this complex notion of a double, made of some etherial, semi-invisible substance, and of which direct experience offers no example. But even supposing that certain dreams rather naturally suggest the animistic explanation, there are certainly many others which are absolutely incompatible with it. Often our dreams are concerned with passed events; we see again the things which we saw or did yesterday or the day before or even during our youth, etc.; dreams of this sort are frequent and hold a rather considerable place in our nocturnal life. But the idea of a double cannot account for them. Even if the double can go from one point to another in space, it is not clear how it could possibly go back and forth in time.