Among the impressions received by a child through his sense organs, some must very early distinguish themselves from the rest. (1) When the child is carried about or creeps about, the majority of his impressions change from moment to moment: instead of a wall with pictures, seen a few seconds ago, he sees windows with curtains; instead of tables and chairs he sees houses, trees, and strange people. Certain impressions, however, hardly change. Whatever else he may see, he almost invariably sees also his hands and some of the lower parts of his body. Whatever may be the position of his body, sensations from his clothing, from the movements of his limbs, from the processes in his digestive and other organs are always present. (2) Another impressive phenomenon is this. The things seen often move, and thus cause alterations in the field of vision. But when these moving things are his own arms and legs, yielding to the pull of their muscles, there is an additional experience, made up of kinesthetic and usually also tactual sensations. Certain experiences are therefore a kind of twofold experience as compared with others which are of one kind only: visual plus kinesthetic-tactual. (3) In still a third way certain experiences distinguish themselves. Whenever the child’s hands and feet come in contact with external things, a tactual sensation is added to the visual impression. But when one hand touches the other hand or a foot or another part of the body, even a part which is not seen, a peculiar double tactual impression is received. That this double tactual sensation is particularly interesting may be concluded from the concentration with which an infant plays with his feet, and the enjoyment which a kitten seems to get from biting its tail. For various reasons, therefore, the sensations of a child’s _own body_, visual, tactual, organic, etc., become experiences of a special class. By various peculiarities they distinguish themselves from all others and become a special, unitary group. But the child’s _ideas and feelings_, when compared with his perceptions, also form a peculiar system, often keeping unchanged while the perceptions change because of movements of the objective things or of the body itself. It is quite natural, then, that in opposition to the external world _a dual system_ is conceived, made up of the bodily sensations on the one hand and the ideas and feelings of frequently repeated or especially impressive experiences on the other. But in spite of this unison between the complex of bodily sensations and the complex of ideas, forming a personal world as opposed to the external world, there remains an opposition between the constituents of the personal world as between a material and a spiritual half of the whole.