Now, whether I am concerned with the ruler, with the paper-knife, or with the mind, have I direct evidence of the existence of anything more than the whole group of qualities?  Do I ever perceive the substance?

In the older philosophy, the substance (substantia) was conceived to be a something not directly perceived, but only inferred to exist—­a something underlying the qualities of things and, as it were, holding them together.  It was believed in by philosophers who were quite ready to admit that they could not tell anything about it.  For example, John Locke (1632-1704), the English philosopher, holds to it stoutly, and yet describes it as a mere “we know not what,” whose function it is to hold together the bundles of qualities that constitute the things we know.

In the modern philosophy men still distinguish between substance and qualities.  It is a useful distinction, and we could scarcely get on without it.  But an increasing number of thoughtful persons repudiate the old notion of substance altogether.

We may, they say, understand by the word “substance” the whole group of qualities as a group—­not merely the qualities that are revealed at a given time, but all those that we have reason to believe a fuller knowledge would reveal.  In short, we may understand by it just what is left when the “we know not what” of the Lockian has been discarded.

This notion of substance we may call the more modern one; yet we can hardly say that it is the notion of the plain man.  He does not make very clear to himself just what is in his thought, but I think we do him no injustice in maintaining that he is something of a Lockian, even if he has never heard of Locke.  The Lockian substance is, as the reader has seen, a sort of “unknowable.”

And now for the doctrine that the mind is nonextended and immaterial.  With these affirmations we may heartily agree; but we must admit that the plain man enunciates them without having a very definite idea of what the mind is.

He regards as in his mind all his sensations and ideas, all his perceptions and mental images of things.  Now, suppose I close my eyes and picture to myself a barber’s pole.  Where is the image?  We say, in the mind.  Is it extended?  We feel impelled to answer, No.  But it certainly seems to be extended; the white and the red upon it appear undeniably side by side.  May I assert that this mental image has no extension whatever?  Must I deny to it parts, or assert that its parts are not side by side?

It seems odd to maintain that a something as devoid of parts as is a mathematical point should yet appear to have parts and to be extended.  On the other hand, if we allow the image to be extended, how can we refer it to a nonextended mind?

To such questions as these, I do not think that the plain man has an answer.  That they can be answered, I shall try to show in the last section of this chapter.  But one cannot answer them until one has attained to rather a clear conception of what is meant by the mind.