About two hundred years ago the philosopher Berkeley pointed out that the distinction commonly made between things as they look, the apparent, and things as they are, the real, is at bottom the distinction between things as presented to the sense of sight and things as presented to the sense of touch.  The acute analysis which he made has held its own ever since.

We have seen that, in walking towards the tree, we have a long series of visual experiences, each of which differs more or less from all of the others.  Nevertheless, from the beginning of our progress to the end, we say that we are looking at the same tree.  The images change color and grow larger.  We do not say that the tree changes color and grows larger.  Why do we speak as we do?  It is because, all along the line, we mean by the real tree, not what is given to the sense of sight, but something for which this stands as a sign.  This something must be given in our experience somewhere, we must be able to perceive it under some circumstances or other, or it would never occur to us to recognize the visual experiences as signs, and we should never say that in being conscious of them in succession we are looking at the same tree.  They are certainly not the same with each other; how can we know that they all stand for the same thing, unless we have had experience of a connection of the whole series with one thing?

This thing for which so many different visual experiences may serve as signs is the thing revealed in experiences of touch.  When we ask:  In what direction is the tree?  How far away is the tree?  How big is the tree? we are always referring to the tree revealed in touch.  It is nonsense to say that what we see is far away, if by what we see we mean the visual experience itself.  As soon as we move we lose that visual experience and get another, and to recover the one we lost we must go back where we were before.  When we say we see a tree at a distance, we must mean, then, that we know from certain visual experiences which we have that by moving a certain distance we will be able to touch a tree.  And what does it mean to move a certain distance?  In the last analysis it means to us to have a certain quantity of movement sensations.

Thus the real world of things, for which experiences of sight serve as signs, is a world revealed in experiences of touch and movement, and when we speak of real positions, distances, and magnitudes, we are always referring to this world.  But this is a world revealed in our experience, and it does not seem a hopeless task to discover what may properly be called real and what should be described as merely apparent, when both the real and the apparent are open to our inspection.

Can we not find in this analysis a satisfactory explanation of the plain man’s claim that under certain circumstances he sees the tree as it is and under others he does not?  What he is really asserting is that one visual experience gives him better information regarding the real thing, the touch thing, than does another.