Normally there is nothing we are more certain of than the feeling of our self, our own ego. It seems to us an independent unitary thing, sharply outlined against everything else. That this is a deceptive appearance, and that on the contrary the ego extends inwards without any sharp delimitation, into an unconscious mental entity which we call the id and to which it forms a facade, was first discovered by psycho-analytic research, and the latter still has much to tell us about the relations of the ego to the id.
