Family life, so far as it is merely on the basis of instinct, takes its place with other agencies favored by natural selection which make for more rational and social existence. Various instincts are more or less at work. The sex instinct brings the man and the woman together. The instinct of jealousy, and the property or possessing instinct, may foster exclusive and permanent relations. The parental instinct and affection bind the parents together and thus contribute to the formation of the social group described in the preceding chapter. Considering now the more immediate relations of husband and wife, parents and children, rather than the more general group relations, we call attention to some of the most obvious aspects, leaving fuller treatment for Part III. The idealizing influences of the sex instinct, when this is subject to the general influences found in group life, is familiar. Lyric song is a higher form of its manifestation, but even a mute lover may be stimulated to fine thoughts or brave deeds. Courtship further implies an adaptation, an effort to please, which is a strong socializing force. If "all the world loves a lover," it must be because the lover is on the whole a likable rôle. But other forces come in. Sex love is intense, but so far as it is purely instinctive it may be transitory. Family life needed more permanence than sex attraction could provide, and before the powerful sanctions of religion, society, and morals were sufficient to secure permanence, it is probable that the property interest of the husband was largely effective in building up a family life, requiring fidelity to the married relation on the part of the wife.