This brief consideration of the trend of people up to the present
time seems to show that, owing to the nature of man himself, especially
to the nature of large "crowds" of men, the direction in which
nations have been moving hitherto has not been toward increasing
the prevalence of peace, but rather toward increasing the methods,
instruments, and areas of war; furthermore, that this direction of
movement has been necessary, in order to achieve and to maintain
prosperity in any nation.

This being the case, what forces exist that may reasonably be expected
to change that trend?

Three main forces are usually mentioned: Civilization, Commerce,
Christianity.

Before considering these it may be well to note Newton's first law
of motion, that every body will continue in a state of rest or of
uniform motion in a straight line unless acted on by some external
force; for though this law was affirmed of material bodies, yet its
applicability to large groups of men is striking and suggestive.
Not only do human beings have the physical attributes of weight and
inertia like other material bodies, but their mental organism,
while of a higher order than the physical, is as powerfully affected
by external forces. And though it is true that psychology has not
yet secured her Newton, and that no one has yet formulated a law
that expresses exactly the action of the minds and spirits of men
under the influence of certain mental and moral stimuli or forces,
yet we know that our minds and spirits are influenced by fear,
hope, ambition, hate, and so forth, in ways that are fairly well
understood and toward results that often can be predicted in advance.