phenomena, the representatives of things, at first hand, how can we
tell that they are representatives? and what becomes of the assumption
that we _perceive_ that mind is related to an external world?

It may be said, this problem the psychologist may leave to the
metaphysician. Certainly, it is one of those problems that the
metaphysician discusses; it has been treated in Chapter IV. But my
contention is, that he who has given no thought to the matter may
easily fall into error as to the very nature of mental phenomena.

For example, when we approach or recede from a physical object we have
a series of experiences which are recognized as sensational. When we
imagine a tree or a house we are also experiencing a mental phenomenon.
All these experiences _seem_ plainly to have extension in some sense of
the word. We appear to perceive plainly part out of part. In so far,
these mental things seem to resemble the physical things which we
contrast with what is mental. Shall we say that, because these things
are mental and not physical, their apparent extension is a delusion?
Shall we say that they really have no parts? Such considerations have
impelled psychologists of eminence to maintain, in flat contradiction
to what seems to be the unequivocal testimony of direct introspection,
that the total content of consciousness at any moment must be looked
upon as an indivisible, part-less unit.

We cannot, then, depend merely on direct introspection. It is too
uncertain in its deliverances. If we would make clear to ourselves
what mental phenomena really are, and how they | differ from physical
phenomena, we must fall back upon the reflective analysis of our
experience which occupies the metaphysician (section 34). Until we
have done this, we are in great danger of error. We are actually