Without the factor of mutual love the proper conditions for procreation cannot exist; without the factor of procreation the sexual union, however beautiful and sacred a relationship it may in itself be, remains, in essence, a private relationship, incomplete as a marriage and without public significance. (en)
The art of love certainly includes such primary facts of sexual hygiene, but it involves also the whole erotic discipline of marriage, and that is why its significance is so great, for the welfare and happiness of the individual, for the stability of sexual unions, and indirectly for the race, since the art of love is ultimately the art of attaining the right conditions for procreation. (en)