organs are specialized. Thus there comes a time when the part split off
carries with it power to eat and digest, to fight or run away, but only
half the power of procreation. This half unit, this incomplete
individual, is either male or female, and from this time on, the epic of
life gathers around the search of these half-lives for their
complements. The force that impels to this search, while at first
valuable only for the perpetuation of the generations, gathers into
itself modifying feeling and desires and, at a later period, ideas and
ideals, which finally, when men and women appear, make it the greatest
of all the shaping forces in life.[1]

[1] The fact that sexual selection does not play the part in organic
evolution which Darwin assigned it does not affect this statement. See
chapter on Sexual Selection in YVES DELAGEE and MARIE GOLDSMITH, _The
Theories of Evolution_, New York: Huebsch, 1912.

Of course, in such a sweeping statement as this, one must include under
sex hunger all the forces that drive men and women to seek each other's
society, rather than that of their own sex. In this sense, it can be
truly said that it gives a motive for our care of offspring, and for
all our other most self-forgetful devotions, our finest altruisms, our
most polished expressions in language, manners and dress. It justifies
labor, ambition, and at times even self-effacement. It underlies nearly
all the lyric expressions in art; furnishes almost the only theme for
that delineation of modern life which we call the novel; and is a main
support for music, painting, statuary and belles-lettres. It gives us
the institution of the family, which is the parent of the state; it is
closely allied to religion; and in our individual lives it lifts us to
the heights of self-realization and happiness, or plunges us down to the
depths of degradation and tragedy.