cy to look at oneself from the
outside, so to speak, a susceptibility to sights and sounds and
impressions that formerly had little influence. Each one is conscious of
new desires, new attractions, expressed often only in a vague feeling of
unrest, with a desire, half shy because half conscious, for the company
of the opposite sex. The childish desire for protection weakens; the
more mature desire to protect others begins to express itself.

Now, the whole significance of these changes, physical and mental, is
fundamentally sexual and social. Human life, it may be said, has a
twofold aspect. As a mere animal organism, there is the perpetuation of
the species, which nature secures by the mere force of the sex impulse.
As a human being, he is part of a social structure, cell in the social
tissue, to use Leslie Stephen's expressive phrase. And in this direction
nature secures what is necessary by the presence of impulses and
cravings as imperious as, and even more permanent than, those of mere
sex. Of course, in practice these two things operate together. By a
process of selection, the anti-social character is weeded out, and the
two sets of feelings work together in harmony for the furtherance and
the development of the life of the species. The species is perpetuated
in the interests of society; society is perpetuated in the interests of
the species. Further, it is part of the natural 'plan' that there shall
be developed impulses and capacities suitable to each phase of life as
it emerges. Thus it has been shown that the lengthening of infancy--that
is, the prolongation of the time during which the young human being is
dependent upon its parents for support and protection--is nature's
method of developing to a greater degree the capacity of the human
animal for more complex adjustment. Instead of being launched on the
world with a number of instincts practically fully developed, and so
capable of attending to its own needs almost as soon as born, man is
born with few instincts, and a great capacity for education enabling him
to adjust his conduct to the demands of an environment constantly
increasing in complexity. In the same way it has been shown that the
instinct for play, practically universal throughout the whole of the
animal world, is nature's method of preparing the young for the more
serious business of nature.[152] It is, therefore, only in line with
what is found to be true elsewhere that the changes incident to