nction is everywhere drawn, and that we must not
obliterate it, is very evident. But we are in the presence of what has
seemed to many men a grave difficulty. Are not things presented in our
experience only as we have sensations? what is it to perceive a thing?
is it not to have sensations? how, then, _can_ we distinguish between
sensations and things? We certainly do so all the time, in spite of
the protest of the philosopher; but many of us do so with a haunting
sense that our behavior can scarcely be justified by the reason.

Our difficulty, however, springs out of an error of our own. Grasping
imperfectly the full significance of the word "sensation," we extend
its use beyond what is legitimate, and we call by that name experiences
which are not sensations at all. Thus the external world comes to seem
to us to be not really a something contrasted with the mental, but a
part of the mental world. We accord to it the attributes of the
latter, and rob it of those distinguishing attributes which belong to
it by right. When we have done this, we may feel impelled to say, as
did Professor Pearson, that things are not really "outside" of us, as
they seem to be, but are merely "projected" outside--thought of as if
they were "outside." All this I must explain at length.

Let us come back to the first of the illustrations given above, the
case of the fire in my study. As I stand and look at it, what shall I
call the red glow which I observe? Shall I call it a _quality of a
thing_, or shall I call it a _sensation_?

To this I answer: _I may call it either the one or the other, according
to its setting among other experiences_.

We have seen (section 15) that sensations and things merely imaginary
are distinguished from one another by their setting. With open eyes we
see things; with our eyes closed we can imagine them: we see what is
before us; we imagine what lies behind our backs. If we confine our
attention to the bit of experience itself, we have no means of
determining whether it is sensory or imaginary. Only its setting can
decide that point. Here, we have come to another distinction of much
the same sort. That red glow, that bit of experience, taken by itself
and abstracted from all other experiences, cannot be called either a
sensation or the quality of a thing. Only its context can give us the
right to call it the one or the other.

This ought to become clear when we reflect upon the illustration o