rge an increase of
mass and a yet larger increase of effective surface through its rich
convolutions. It is through educability of this order that the human
child is brought intellectually and affectively into touch with the
ideal constructions by means of which man has endeavoured, with more
or less success, to reach an interpretation of nature, and to guide the
course of the further evolution of his race--ideal constructions which
form part of man's environment.

It formed no part of Darwin's purpose to consider, save in broad
outline, the methods, or to discuss in any fulness of detail the results
of the process by which a differentiation of the mental faculties of
man from those of the lower animals has been brought about--a
differentiation the existence of which he again and again
acknowledges. His purpose was rather to show that, notwithstanding
this differentiation, there is basal community in kind. This must be
remembered in considering his treatment of the biological foundations
on which man's systems of ethics are built. He definitely stated that he
approached the subject "exclusively from the side of natural history."
("Descent of Man", Vol. I. page 149.) His general conclusion is that the
moral sense is fundamentally identical with the social instincts, which
have been developed for the good of the community; and he suggests
that the concept which thus enables us to interpret the biological
ground-plan of morals also enables us to frame a rational ideal of the
moral end. "As the social instincts," he says (Ibid. page 185.), "both
of man and the lower animals have no doubt been developed by nearly the
same steps, it would be advisable, if found practicable, to use the same
definition in both cases, and to take as the standard of morality,
the general good or welfare of the community, rather than the general
happiness." But the kind of community for the good of which the social
instincts of animals and primitive men were biologically developed may
be different from that which is the product of civilisation, as Darwin
no doubt realised. Darwin's contention was that conscience is a social
instinct and has been evolved because it is useful to the tribe in the
struggle for existence against other tribes. On the other hand, J.S.
Mill urged that the moral feelings are not innate but acquired, and Bain
held the same view, believing that the moral sense is acquired by each
individual during his life-time. Darwin, who