sm between body and soul is broken
down, as psychology becomes an ally of physiology and biology, and
biology joins hands with physics and chemistry, we are taught to see
that there is a mysterious unity between these inner and outer forces.
They express themselves in accordance with the same structural, physical
and chemical laws. The development of civilization in the subjective
world, in the sphere of behavior, conduct and morality, has been
precisely the gradual accumulation and popularization of methods which
teach people how to direct, transform and transmute the driving power of
the great natural forces.

Psychology is now recognizing the forces concealed in the human
organism. In the long process of adaptation to social life, men have
had to harness the wishes and desires born of these inner energies,
the greatest and most imperative of which are Sex and Hunger. From
the beginning of time, men have been driven by Hunger into a thousand
activities. It is Hunger that has created "the struggle for existence."
Hunger has spurred men to the discovery and invention of methods and
ways of avoiding starvation, of storing and exchanging foods. It has
developed primitive barter into our contemporary Wall Streets. It has
developed thrift and economy,--expedients whereby humanity avoids the
lash of King Hunger. The true "economic interpretation of history" might
be termed the History of Hunger.

But no less fundamental, no less imperative, no less ceaseless in its
dynamic energy, has been the great force of Sex. We do not yet know the
intricate but certainly organic relationship between these two forces.
It is obvious that they oppose yet reinforce each other,--driving,
lashing, spurring mankind on to new conquests or to certain ruin.
Perhaps Hunger and Sex are merely opposite poles of a single great
life force. In the past we have made the mistake of separating them
and attempting to study one of them without the other. Birth Control
emphasizes the need of re-investigation and of knowledge of their
integral relationship, and aims at the solution of the great problem of
Hunger and Sex at one and the same time.

In the more recent past the effort has been made to control, civilize,
and sublimate the great primordial natural force of sex, mainly by
futile efforts at prohibition, suppression, restraint, and extirpation.
Its revenge, as the psychoanalysts are showing us every day, has been
great. Insanity, hysteria, neuroses