changes its skin. This is its whole existence, which certainly does
not lead us to expect a display of any, even the most limited,
intellectual power. When, however, the time comes for the larva of
this moth to become a chrysalis, it spins for itself a double cocoon,
fortified with bristles that point outwards, so that it can be opened
easily from within, though it is sufficiently impenetrable from
without. If this contrivance were the result of conscious
reflection, we should have to suppose some such reasoning process as
the following to take place in the mind of the caterpillar:- "I am
about to become a chrysalis, and, motionless as I must be, shall be
exposed to many different kinds of attack. I must therefore weave
myself a web. But when I am a moth I shall not be able, as some
moths are, to find my way out of it by chemical or mechanical means;
therefore I must leave a way open for myself. In order, however,
that my enemies may not take advantage of this, I will close it with
elastic bristles, which I can easily push asunder from within, but
which, upon the principle of the arch, will resist all pressure from
without." Surely this is asking rather too much from a poor
caterpillar; yet the whole of the foregoing must be thought out if a
correct result is to be arrived at.

This theoretical separation of instinct from conscious intelligence
can be easily misrepresented by opponents of my theory, as though a
separation in practice also would be necessitated in consequence.
This is by no means my intention. On the contrary, I have already
insisted at some length that both the two kinds of mental activity
may co-exist in all manner of different proportions, so that there
may be every degree of combination, from pure instinct to pure
deliberation. We shall see, however, in a later chapter, that even
in the highest and most abstract activity of human consciousness