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. Our whole theory of government and our laws of business and every-day life are founded on the belief that men are the same to-day as they were yesterday, and that they will be the same to-morrow. The whole science of psychology is based on the observed and recorded actions of the human organism under the influence of certain external stimuli or forces, and starts from the assumption that this organism has definite and permanent characteristics. If this is not so--if the behavior of men in the past has not been governed by actual laws which will also govern their behavior in the future--then our laws of government are built on error, and the teachings of psychology are foolish.