n. Yet vision performs
this miracle. In a certain sense the blind man is right, since vision,
having its origin in the stimulation of the retina, by the vibrations of
the light, is nothing else, in fact, but a retinal touch. Such is indeed
the _scientific_ explanation, for the function of science is just to
express all perceptions in terms of touch. But we have shown elsewhere
that the philosophical explanation of perception (if it may still be
called an explanation) must be of another kind.[67] Now instinct also is
a knowledge at a distance. It has the same relation to intelligence that
vision has to touch. Science cannot do otherwise than express it in
terms of intelligence; but in so doing it constructs an imitation of
instinct rather than penetrates within it.

Any one can convince himself of this by studying the ingenious theories
of evolutionist biology. They may be reduced to two types, which are
often intermingled. One type, following the principles of neo-Darwinism,
regards instinct as a sum of accidental differences preserved by
selection: such and such a useful behavior, naturally adopted by the
individual in virtue of an accidental predisposition of the germ, has
been transmitted from germ to germ, waiting for chance to add fresh
improvements to it by the same method. The other type regards instinct
as lapsed intelligence: the action, found useful by the species or by
certain of its representatives, is supposed to have engendered a habit,
which, by hereditary transmission, has become an instinct. Of these two
types of theory, the first has the advantage of being able to bring in
hereditary transmission without raising grave objection; for the
accidental modification which it places at the origin of the instinct is
not supposed to have been acquired by the individual, but to have been
inherent in the germ. But, on the other hand, it is absolutely incapable
of explaining instincts as sagacious as those of most insects. These
instincts surely could not have attained, all at once, their present
degree of complexity; they have probably evolved; but, in a hypothesis
like that of the neo-Darwinians, the evolution of instinct could have
come to pass only by the progressive addition of new pieces which, in
some way, by happy accidents, came to fit into the old. Now it is
evident that, in most cases, instinct could not have perfected itself by
simple accretion: each new piece really requires, if all is not to be
spoil