For no conclusive solution of the population question is possible under any system. It has been a fundamental difficulty since the beginning of human society, and more than anything else may be regarded as the key to history. The migrations, wars, and conquests recorded in history have for the most part had their origin in want caused by the pressure of population on the extant means of subsistence. No doubt, ambition, vanity, suspicion, and restlessness have played a very considerable part of their own in the military annals of the race, but not nearly so large a part as is generally supposed. Historians have not given anything like adequate attention to the economic factors which have often so decisively operated in human affairs. In its most comprehensive form, indeed, the population question does not concern the immediate future, for the world is not nearly replenished with human beings. In all the countries dominated by European civilisation, wealth has, owing to the vast mechanical development of the last hundred years, increased much more rapidly than population. But the question is one which does already practically concern the more populous centres over large areas of the world. In many of the old seats of population, both in Europe and the East, the struggle for existence is intense, and if not strongly counteracted, must tend to the increase of egotism, unscrupulousness, and general demoralisation. This is most observable in cases where a large population has to face the prospect of a declining prosperity. If the prosperity of this country were menaced by a great war, or a great shock to the national credit, or by both together, or simply by the slow decline of its industrial and commercial supremacy, the struggle for existence in our large towns would be unspeakable.