Such considerations, especially when taken together with what has been said at the close of the last section about the futility of looking for a reality behind our sensations, may easily suggest rather a startling possibility.  May it not be, if we really are shut up to the circle of our experiences, that the physical things, which we have been accustomed to look upon as non-mental, are nothing more than complexes of sensations?  Granted that there seems to be presented in our experience a material world as well as a mind, may it not be that this material world is a mental thing of a certain kind—­a mental thing contrasted with other mental things, such as imaginary things?

This question has always been answered in the affirmative by the idealists, who claim that all existence must be regarded as psychical existence.  Their doctrine we shall consider later (sections 49 and 53).  It will be noticed that we seem to be back again with Professor Pearson in the last chapter.

To this question I make the following answer:  In the first place, I remark that even the plain man distinguishes somehow between his sensations and external things.  He thinks that he has reason to believe that things do not cease to exist when he no longer has sensations.  Moreover, he believes that things do not always appear to his senses as they really are.  If we tell him that his sensations are the things, it shocks his common sense.  He answers:  Do you mean to tell me that complexes of sensation can be on a shelf or in a drawer? can be cut with a knife or broken with the hands?  He feels that there must be some real distinction between sensations and the things without him.

Now, the notions of the plain man on such matters as these are not very clear, and what he says about sensations and things is not always edifying.  But it is clear that he feels strongly that the man who would identify them is obliterating a distinction to which his experience testifies unequivocally.  We must not hastily disregard his protest.  He is sometimes right in his feeling that things are not identical, even when he cannot prove it.

In the second place, I remark that, in this instance, the plain man is in the right, and can be shown to be in the right.  “Things” are not groups of sensations.  The distinction between them will be explained in the next section.

17.  THE DISTINCTION BETWEEN SENSATIONS AND “THINGS”—­Suppose that I stand in my study and look at the fire in the grate.  I am experiencing sensations, and am not busied merely with an imaginary fire.  But may my whole experience of the fire be summed up as an experience of sensations and their changes?  Let us see.

If I shut my eyes, the fire disappears.  Does any one suppose that the fire has been annihilated?  No.  We say, I no longer see it, but nothing has happened to the fire.

Again, I may keep my eyes open, and simply turn my head.  The fire disappears once more.  Does any one suppose that my turning my head has done anything to the fire?  We say unhesitatingly, my sensations have changed, but the fire has remained as it was.