f the
fire. We have seen that one whole series of changes has been
unhesitatingly described as a series of changes in my sensations. Why
was this? Because it was observed to depend upon changes in the
relations of my body, my senses (a certain group of experiences), to
the bit of experience I call the fire. Another series was described as
a series of changes in the fire. Why? Because, the relation to my
senses remaining unchanged, changes still took place, and had to be
accounted for in other ways.

It is a matter of common knowledge that they can be accounted for in
other ways. This is not a discovery of the philosopher. He can only
invite us to think over the matter and see what the unlearned and the
learned are doing at every moment. Sometimes they are noticing that
experiences change as they turn their heads or walk toward or away from
objects; sometimes they abstract from this, and consider the series of
changes that take place independently of this.

That bit of experience, that red glow, is not related only to my body.
Such experiences are related also to each other; they stand in a vast
independent system of relations, which, as we have seen, the man of
science can study without troubling himself to consider sensations at
all. This system is the external world--the external world as known or
as knowable, the only external world that it means anything for us to
talk about. As having its place in this system, a bit of experience is
not a sensation, but is a quality or aspect of a thing.

Sensations, then, to be sensations, must be bits of experience
considered in their relation to some organ of sense. They should never
be confused with qualities of things, which are experiences in a
different setting. It is as unpardonable to confound the two as it is
to confound sensations with things imaginary.

We may not, therefore, say that "things" are groups of sensations. We
may, if we please, describe them as complexes of qualities. And we may
not say that the "things" we perceive are really "inside" of us and are
merely "projected outside."

What can "inside" and "outside" mean? Only this. We recognize in our
experience two distinct orders, the _objective order_, the system of
phenomena which constitutes the material world, and the _subjective
order_, the order of things mental, to which belong sensations and
"ideas." That is "outside" which belongs to the objective order. The
word has no other m