On the other hand, what can be proved is this: that the vitality of a people depends first and foremost on the capacity and willingness of its women to bear and foster children fit to live, and on their husbands’ capacity and willingness to protect the national existence. In the next place, it depends on the whole people’s fondness for work and ability in the achievement of prosperity for itself and of value for mankind at large, and finally on the will of the individual to sacrifice his own ends when the common weal demands it. What can further be proved is that, if a people wastes its strength in sexual dissipation, this will often prevent its fulfilling the conditions we have mentioned as necessary to its progress, and will thus bring about its ruin. But this does not involve any proof that a nation will be ruined if it alters the forms of sexual life according to a newly-acquired knowledge of the most reasonable sexual morality! Monogamy was victorious from many causes, above all from experience of its advantages. It minimised the struggle of the men for the women and thus economised forces for other ends; it provided an incentive to work for offspring; it developed modesty and tenderness within the sexual relationship and thus raised the position of the woman and with it her importance in the bringing-up of the children; it provided them and her with a protection against the arbitrary will of the husband; through home life it fostered self-command and co-operation; the need of the two for each other led to mutual kindness. The authority of the husband was ennobled by the sense of responsibility and the joy of protection; the dependence of the wife by devotion and fidelity. This last was strengthened by fear of the husband’s proprietary jealousy, by his craving for the certainty that his property would be inherited by his own children; by religions, according to which the admixture of foreign blood in the race was a sin; by the hope of Christianity for a life together beyond the grave; and by their common children, the feeling of tenderness for whom grew deeper as development proceeded. And monogamy still continues to exercise this cultivating influence on the morals and on the soul. It might, therefore, seem that this admission of the value of even an imperfect monogamy rendered all further proof unnecessary for those who assert that the true development of sexual morality can only be secured through a gradually perfected monogamy. But they forget that monogamy, which was a custom long before the introduction of Christianity, _became injurious as well as beneficial to true sexual morality, from the moment the Church prescribed it as the only form of this morality_.