A question of importance is at what _age_ the sexual enlightenment can most wisely be effected. Some advise that enlightenment should begin with our answers to the first questions the child propounds upon the subject; others contend that it is better to wait till it is somewhat older than this. There is truth in both these views; but the matter and manner of our communications must be appropriate to the age of the child with which we are dealing. When a young man is being sent to the university, it is wise to instruct him concerning the dangers of venereal infection; but to inform him that human beings come into the world as the result of an act of sexual intercourse would be altogether superfluous. Conversely, if a child asks its parents where its little brother has come from, we do not need to say anything about syphilis and gonorrhoea; but none the less we can give such a child an account suitable for one of its age of the way in which human beings come into the world. Speaking generally, it may be said that the biology and physiology of reproduction--that is to say, the objective processes--may be described at a comparatively early age; but that cautions regarding masturbation should not, _in average cases_, be given before the age of thirteen or fourteen; and that instruction about the risks of venereal infection should be deferred until even later than this. In the case of boys, in so far as enlightenment in the school is concerned, information about venereal infection may, for practical reasons, best be given about the time the boys are preparing to leave for a higher school. In the case of girls, for whom a caution against risks of impregnation and against prostitution are especially in question, we have also, as far as sexual enlightenment in the school is under consideration, to recommend the time when they are about to leave school. But if we prefer that sexual enlightenment, or at any rate a part of such enlightenment, should be effected at home rather than in the school (a course which I regard as essentially preferable), it will be impossible to lay down a fixed rule as to the age at which this should take place. To a lively girl of twelve or thirteen years, a great deal can be said far better by the mother, than can be said to a girl considerably older, say at fifteen, by the school physician, schoolmaster, or schoolmistress. Speaking generally, in the case of girls, the enlightenment may well begin at a somewhat earlier age than in the case of boys--at any rate as regards the subjective processes of the sexual life.