Given the world as it is, the conditions of marriage as they are, the economic position of woman, the power of prudery, and the conventional supposition that babies occur by providential dispensation, we must act as if we really made the assumption that human parenthood, until the moment of birth, is as irresponsible as any sequence of events in the atmosphere or the world of electrons. But we who are thinking in front for humanity must make no such assumption. We must look forward to and hasten the time when we can act upon the _true_ assumption, which is that the more the knowledge the greater the responsibility, and more especially that our knowledge of heredity, so far from abolishing human responsibility--as the enemies of knowledge declare--immeasurably extends and deepens it. In the present volume we are proceeding upon the true assumption, and therefore in the study of womanhood we must now proceed, in defiance of conventional assumptions, to study the responsibility and duties of motherhood _as they exist for maidenhood_. To this end, it will be necessary that we remind ourselves of certain great biological facts which are of immense significance for mankind, and are doubtless indeed more important in their bearing upon ourselves than upon any other living species. The first of these is the fact of heredity; the second the fact that hereditary endowment, whether for good or for evil, or, as is the rule, both for good and for evil, goes vastly further than any one has until lately realized, in determining individual destiny. These are amongst the first principles of Eugenics or race culture, and as they have been discussed at length elsewhere, one may here take them for granted. Scarcely less important is the fact that the conditions of mating in the sub-human world--conditions which beyond dispute make for the continuance, the vigour, the efficiency, and therefore the happiness of the species--are largely modified amongst ourselves in consequence of certain human facts which have no sub-human parallel. The parallels and the divergences between the two cases are both alike of the utmost significance, and cannot be too carefully studied. It will here be possible, of course, merely to look at them as briefly as is compatible with the making of a right approach to the subject now before us, which is the girl's choice of a husband. But in right priority to the question of choice, we may for convenience discuss first the marriage age. The choice at one age may not be the choice at another, and in any case the question of the marriage age is so important for the individual woman, and so immensely effective in determining the composition of any society, that we cannot study it too carefully. XIV THE MARRIAGE AGE FOR GIRLS