The sexual enlightenment of children is absolutely necessary for the following reasons. (_a_) The sexual life conceals many dangers for the child, and the latter will better be able to guard against those dangers if he is aware of their existence. No one has the right to put a sharp knife in a child’s hand without pointing out the dangers of the weapon. But the forces of the sexual life, when ill-understood and ill-controlled, are far more powerful and far more dangerous than the sharpest knife. He who will learn to walk and to run must risk stumbling and falling, and no one can learn to swim without swallowing a little water. (_b_) That which is half-concealed is far more stimulating than that which is revealed. If children are not properly enlightened concerning the sexual life, they become accustomed to regard matters of sex solely from the standpoint of personal desire and personal enjoyment, and to regard the sexual life and the other sex as something hateful and despicable. (_c_) If the child receives no enlightenment concerning the sexual life, its confidence in its teacher and its relatives is necessarily undermined. How shall a child retain confidence in those who give it no advice in a matter in which the need of advice is so urgently felt? Can the child be expected to follow their advice in other departments of life, when in this department it receives bad advice or none at all? Can a child give confidence to its elders in other matters, when in this matter it is fobbed off with lies and fables? The following arguments are adduced against the sexual enlightenment of children. (_a_) It is better, supposing that the sexual impulse has not yet awakened in a child, that nothing should be done to direct its attention to the sexual life. (_b_) The enlightenment of children is a very difficult matter, and is, in fact, hardly practicable. The former of these arguments is not altogether groundless. But in present conditions silence is impossible, and it is better that the child should obtain its information from a pure and trustworthy source. With regard to the alleged difficulty of effecting the sexual enlightenment, recent experience shows that the requisite instruction can be suitably and inconspicuously introduced into the natural history lessons, and adapted to the age and intelligence of the child, without any excessive detail being attempted. The stress has to be laid, not upon enlightenment as to the processes of sexual conjugation, nor upon detailed instruction as to the development of the human embryo, but rather upon a mainly hygienic enlightenment concerning the dangers attendant upon sexual intercourse.