from the practical question whether war is a necessity to maintain the efficiency and energy of nations and to prevent them sinking into sloth and degeneracy. The {128} problem may be stated in another form. When we take a comprehensive survey of the natural history of man—using that term to include the whole of his capacities, activities, and needs, physical, intellectual, moral—do we find that war is the indispensable instrument whereby his survival and progress as a species are maintained? We are assuming in this statement that progress or increased elaboration is to continue to be a necessary tendency in his course by which his fate, through the action of inherited needs, powers, and weaknesses, and of external pressure is irrevocably conditioned. The assumption, though commonly made, is by no means obviously true. Some of the evidence justifying it will be dealt with later; it will not be necessary here to do more than note that we are for the moment treating the doctrine of human progress as a postulate.
Man is unique among gregarious animals in the size of the major unit upon which natural selection and its supposedly chief instrument, war, is open to act unchecked. There is no other animal in which the size of the unit, however laxly held together, has reached anything even remotely approaching the inclusion of one-fifth or one-quarter of the whole species. It is plain that a mortal contest between two units of such a monstrous size introduces an altogether new mechanism into the hypothetical “struggle for existence” on which the conception of the biological necessity of war is founded. It is clear that that doctrine, if it is to claim validity, must contemplate at any rate the possibility of a war of extremity, even of something like extermination, which shall implicate perhaps a third of the whole human race. There is no parallel in biology for progress being accomplished as the result of a racial impoverishment so extreme, even if it were accompanied by a closely specific {129} selection instead of a mere indiscriminate destruction. Progress is undoubtedly dependent mainly on the material that is available for