The fourth book takes Emile from the age of fifteen to twenty. At this period the sex interests appear and should be properly guided and trained, especially as they are the basis of social and moral relationships. Emile’s first passion calls him into relations with his species, and he must now learn to live with others. “We have formed his body, his senses, and his intelligence; it remains to give him a heart.” He is to become moral, affectionate, and religious. Here again Rousseau insists that the training is not to be accomplished by the formal method of precepts, but in a natural way by bringing the youth into contact with his fellowmen and appealing to his emotions. Emile is to visit infirmaries, hospitals, and prisons, and witness concrete examples of wretchedness in all stages, although not so frequently as to become hardened. That this training may not render him cynical or hypercritical, it should be corrected by the study of history, where one sees men simply as a spectator without feeling or passion. Further, in order to deliver Emile from vanity, so common during adolescence, he is to be exposed to flatterers, spendthrifts, and sharpers, and allowed to suffer the consequences. He may at this time also be guided in his conduct by the use of fables, for “by censuring the wrongdoer under an unknown mask, we instruct without offending him.” [Sidenote: The passive and parasitic education of woman.] Emile at length becomes a man, and a life companion must be found for him. A search should be made for a suitable lady, but “in order to find her, we must know her.” Accordingly, the last book of the Emile deals with the model Sophie and the education of woman. It is the weakest part of Rousseau’s work. He entirely misinterprets the nature of women, and does not allow them any individuality of their own, but considers them as simply supplementary to the nature of men. Like men, women should be given adequate bodily training, but rather for the sake of physical charms and of producing vigorous offspring than for their own development. Their instinctive love of pleasing through dress should be made of service by teaching them sewing, embroidery, lacework, and designing. They ought to be obedient and industrious, and they ought early to be brought under restraint. Girls should also be taught singing, dancing, and other accomplishments. They should be instructed dogmatically in religion, and in ethical matters they should be largely guided by public opinion. A woman may not learn philosophy, art, or science, but she should study men. “She must learn to penetrate their feelings through their conversation, their actions, their looks, and their gestures, and know how to give them the feelings which are pleasing to her, without even seeming to think of them.” [Sidenote: Defects outweighed by merits.]