So inadequate, indeed, does the agency of natural selection seem to be
to eliminate illusion, that it may even be asked whether its tendency
may not be sometimes to harden and fix rather than to dissolve and
dissipate illusory ideas and beliefs. It will at once occur to the
reader that the illusion of self-esteem, discussed in the last chapter,
may have been highly useful as subserving individual self-preservation.
In a similar way, it has been suggested by Schopenhauer that the
illusion of the lover owes its force and historical persistence to its
paramount utility for the preservation of the species. And to pass from
a recurring individual to a permanently common belief, it is maintained
by the same pessimist and his followers that what they regard as the
illusion of optimism, namely, the idea that human life as a whole is
good, grows out of the individual's irrational love of life, which is
only the same instinctive impulse of self-preservation appearing as
conscious desire. Once more, it has been suggested that the belief in
free-will, even if illusory, would be preserved by the process of
evolution, owing to its paramount utility in certain stages of moral
development. All this seems to show at least the possibility of a kind
of illusion which would tend to perpetuate itself, and to appear as a
permanent common belief.

Now, so far as this is the case, so far as illusion is useful or only
harmless, natural selection cannot, it is plain, be counted on to weed
it out, keeping it within the narrow limits of the exceptional and
individual. Natural selection gets rid of what is harmful only, and is
indifferent to what is practically harmless.

It may, however, still be said that the process of direct adaptation
must tend to establish such a consensus of true belief. Now, I do not
wish for a moment to dispute that the growth of intelligence by the
continual exercise of its functions tends to such a consensus: this is
assumed to be the case by everybody. What I want to point out is that
there is no scientific proof of this position.

The correspondence of internal to external relations is obviously
limited by the modes of action of the environment on the organism,
consequently by the structure of the organism itself. Scientific men are
familiar with the idea that there may be forces in the environment which
are practically inoperative on the organism, there being no
corresponding mode of sensibility. And even if it be s