The mystery of self-existence has probably been a puzzle to many a thoughtful child. A lady, a well-known writer of fiction, sends me the following recollection of her early thought on this subject: “The existence of other people seemed natural: it was the ‘I’ that seemed so strange to me. That I should be able to perceive, to think, to cause other people to act, seemed to me quite to be expected, but the power of feeling and acting and moving about myself, under the guidance of some internal self, amazed me continually.” It is of course hard to say how exactly the child thinks about this inner self. It seems to me probable that, allowing for the great differences in reflective power, children in general, like uncivilised races, tend to materialise it, thinking of it dimly as a film-like shadow-like likeness of the visible self. The problem is complicated for the child’s consciousness by religious instruction with its idea of an undying soul. As may be seen in the recollections just quoted, this early thought about self is greatly occupied with its action on the body. Among the many things that puzzled the much-questioning little lad already frequently quoted was this: “How do my thoughts come down from my brain to my mouth: and how does my spirit make my legs walk?” C.’s sister when four years and ten months old wanted to know how it is we can move our arm and keep it still when we want to, while the curtain can’t move except somebody moves it. The first attempts to solve the puzzle are of course materialistic, as may be seen in our little questioner’s delightful notion of thoughts travelling through the body. This form of materialism, however, I find surviving in grown-ups and even in students of psychology, who are rather fond of talking about sensations travelling up the nerves to the brain.