organs of sense. Their peculiarities determine what is the nature of
the outside world which we construct. It is the similarity in the
organs of sense and in the perceptive faculty of all normal human
beings which makes the outside world the same, or _practically_ the
same, for them all. To return to the old analogy, it is as if two
telephone exchanges had very nearly identical groups of subscribers.
In this case a wire between the two exchanges would soon convince the
imprisoned clerks that they had something in common and peculiar to
themselves. That conviction corresponds in our comparison to the
recognition of other consciousness."

I suggest that this extract be read over carefully, not once but
several times, and that the reader try to make quite clear to himself
the position of the clerk in the telephone exchange, _i.e._ the
position of the mind in the body, as depicted by Professor Pearson,
before recourse is had to the criticisms of any one else. One cannot
find anywhere better material for critical philosophical reflection.

As has been seen, our author accepts without question, the
psychological doctrine that the mind is shut up within the circle of
the messages that are conducted to it along the sensory nerves, and
that it cannot directly perceive anything truly external. He carries
his doctrine out to the bitter end in the conclusion that, since we
have never had experience of anything beyond sense-impressions, and
have no ground for an inference to anything beyond, we must recognize
that the only external world of which we know anything is an external
world built up out of sense-impressions. It is, thus, in the mind, and
is not external at all; it is only "projected outwards," _thought of_
as though it were beyond us. Shall we leave the inconsistent position
of the plain man and of the psychologist and take our refuge in this