It may perhaps be thought that the whole difficulty arises simply because what we are trying to think consistently about is a reality that is external to us. Space and time, movement, cause and effect are ideas that apply to a world outside and independent of the mind that tries to think it. May not this be the reason of our failure and the whole explanation of the seeming contradiction? If we turn our thoughts inward upon our own being and think of the self, the I, the real subject of experience, then surely where thought is at home and its object is mental not physical, we shall know reality. It is not so. The same self-contradiction characterises our ideas when we try to present the real object of inner perception as when we try to present the real object of external perception. Not, of course, that it is possible to doubt the reality of our own existence, but that we fail altogether to express the meaning of the self we so surely know to exist in any idea which does not fall into self-contradiction. As in the case of the thing and its qualities, we think that there is something distinct from the qualities in which they inhere and yet find ourselves unable to present to the mind any consistent idea of such thing, so we think that there must be some substance or basis of personal identity, some real self which _has_ the successive changing conscious states, which has the character which distinguishes our actions as personal but which nevertheless _is_ not itself these things. The self-contradiction { 37} in the idea of self, or I, or subject, is that it both cannot change and is always changing. As unchanging, we distinguish it from our body, which is an external object among other objects and is different from other objects only in the more direct and intimate relation in which it stands to us. The body is always changing; never for two successive moments is it exactly the same combination of chemical elements. We distinguish also ourself from that consciousness which is memory, the awareness of past experience, from present feelings, desires, thoughts, and strivings--these, we say, belong to the self but are not it. The self must have qualities and dwell in the body, guiding, directing, and controlling it, yet this self we never perceive, nor can we conceive it, for our idea of it is of a reality that changes and is yet unchangeable.