No national entity can resist the attacks of others if its numerical strength is comparatively small. If a contest takes place between two nations whose numerical strength is approximately equal, the healthier of the two will gain the victory. Even in prehistoric times a minimal degree of Child-Protection was indispensable to tribal existence. To rear children diminished, indeed, the quantity of wealth available to maintain the life of the parents, and consequently rendered even more difficult than before the struggle with the hostile forces of nature. None the less, it was absolutely essential to rear a minimal number of children. A sufficient number of boys must be reared to maintain the ranks of the warriors needed for the protection of the tribe against the attacks of its neighbours; and since tribal wars were unceasing, the number requisite to replace those who fell in battle was considerable; girls also must be reared in numbers sufficient to be the mothers of the required number of warriors. But it was against the tribal interest that more children than these should come into the world; and it was desirable that superfluous infants should perish. The most important factors in human evolution are the quantity and the quality of individual human beings. Until quite recently it is only upon quantity of population that any stress has been laid: the quality of the population has been ignored; being either taken for granted, or regarded as dependent upon chance conditions. The problems of population were not recognised as quantitative and qualitative, but were believed to be quantitative merely. Both Socialism and Child-Protection have intimate associations alike with the quantitative and with the qualitative problems of population. Both Socialism and Child-Protection exert a powerful influence upon the quantity and the quality of human beings; and conversely these latter react no less powerfully upon Socialism and Child-Protection. The leading aim of Child-Protection is to prevent the death of children before they attain an age at which they become competent to contribute directly to the welfare of society. The next most important aim of Child-Protection is to ensure that the individual whose life has been preserved shall not become useless or dangerous to society. These leading aims may be pithily summarised in the following terms: “the prevention of a high mortality-rate,” and “the prevention of a high criminality-rate.” The main factor of a high mortality-rate is excessive mortality in childhood; and the main factor of a high criminality-rate is excessive criminality in childhood. (The rate of mortality affects the quantitative element, and the rate of criminality affects the qualitative element, of the race.)