_This book is endorsed by the Society for the Prevention of Venereal Disease and contains the evidence and arguments on which the Society bases its policy, and is addressed to all who would prevent venereal diseases in themselves or in the community._ Children may be taught any system of morals--sexual or other; Christian, Mahomedan, Hindoo, Papuan, or other. They are intensely imitative and acquire a bias towards local ideas of right and wrong through association with intimate companions. A bias once acquired tends to persist. For that reason parents choose good companions and schools. On the other hand, it is difficult or impossible to convert "hardened sinners," for example, adult non-Christians. Children, therefore, may be really taught; adults, as a rule, can only be preached at. Any man may test the truth of all this by examining his own consciousness. Would any amount of preaching cause him to change his present ideas of right and wrong? As little can he alter the bias of other men. As the twig is bent so the tree grows. In various times and places, almost everything from promiscuous sexual intercourse to absolute abstinence from all intercourse has been held holy, or permissible, or damnable. Even among Christians the widest differences have prevailed as regards the local and contemporary tone. Among them, especially among the English speaking peoples, a convention forbids the familiar discussion of sexual matters between children and adults. This convention may be right or wrong. In any case it exists, and is likely to persist for ages. But a knowledge of sex is traditional among boys, and to some extent among girls of the school age. For good or evil, therefore, children are the real teachers of sexual morals in England. Children deal with the impressionable age and give the early bias. Adults stand aside, and teach only extreme reticence. The discussions of boys are often obscene. As a consequence vast numbers grow up with the idea that unchastity is a gallant adventure, or, at worst, only a peccadillo. Even in old age such men look back to past intrigues with satisfaction. After marriage another tradition, or bias, also taught by English boys, comes into action--the tradition to keep the plighted word, to "play the game." The great majority of married Englishmen, therefore, are chaste.