What are the conditions of life upon this earth? Is there war or peace in daily life? All living beings require food; they multiply in a geometrical ratio; and so the _natural_ productivity of the soil becomes increasingly inadequate. The tendency to increase in geometrical ratio is true of all life—vegetable, animal and human, but the tendency is checked by various counteracting influences, natural and artificial. A short time ago these checks had so operated to annul the law of increase as almost to stop the growth of human population. It is only by the time-binding capacity of man—by scientific progress and technological invention—that the checks have been overcome. And so in the last century the population of Europe increased more than it had increased in several centuries before. Impoverished soil, excessive heat or cold, excessive moisture, the lack of rain-fall, and many other factors are hostile to life. It is evident, therefore, that human life must especially struggle for existence; it must carry on a perpetual contest for self preservation. It seems obvious that, if there is perpetual war in every-day life, war methods must be applied. We have just passed through a tremendous world-wide _military_ war and we developed special ways of producing power to overcome the enemy. We were thus driven to discover some of the hidden sources of power and all of our old habits and ideas were bent toward military methods and military technology. The war of every-day life against hostile elements is war for the subjugation of physical nature and not for the conquest of people. It is a war carried on by the time-binding power of men pitted against natural obstacles, and its progressive triumph means progressive advancement in human weal. The lesson of the World War should not be missed through failure to analyse it. When nations war with nations, the normal daily war of millions and millions of individuals to subjugate natural resources to human uses is interrupted, and the slow-gathered fruits of measureless toil are destroyed. But peaceful war, war for the conquest of nature, involves the use of methods of technology and, what is even more important, technological philosophy, law and ethics. What I want to emphasize in this little book, is the need of a thoroughgoing revision of our ideas; and the revision must be made by engineering minds in order that our ideas may be made to match facts. If we are ill, we consult a physician or a surgeon, not a charlatan. We must learn that, when there is trouble with the producing power of the world, we have to consult an engineer, an expert on power. Politicians, diplomats, and lawyers do not understand the problem. What I am advocating is that we must learn to ask those who know how to produce things, instead of asking those whose profession is to fight for the division of things produced by nature or by other human beings.