Sexual morality is twice mentioned in the ten commandments of Moses:
Seventh commandment: Thou shall not commit adultery.
Tenth commandment: Thy shall not covet thy neighbor's wife, nor his man servant, nor his maid servant, nor his ox, nor his ass, nor anything that is thy neighbor's.
In the eleventh commandment of Jesus Christ the words: Thou shall love thy neighbor as thyself, represent approximately the point of view of modern ethics. Nevertheless contemporary social progress requires more and better. It is not so exalted as to say "Love those who persecute you," but it demands a more rational and better formulated ethics, somewhat as follows: Thou shall love humanity more than thyself, and thou shalt seek thy happiness in the welfare of its future. Such a formula expresses the commandment of sexual ethics as we have defined it.
In the commandments of Moses the wife is regarded as property, and the desire for the wife of one's neighbor is threatened with divine punishment inasmuch as it covets the property of one's neighbor. When woman is treated as a free subject and as the equal and companion of man, it is evident that a fundamental revision of such ideas is requisite. Certain forms of adultery with voluntary consent on both sides may even become positive from the moral point of view.
In spite of this, one of the principal tasks of man's sexual morality will always be to restrain his erotic polygamous desires, for the simple reason that they are especially apt to injure the rights and the welfare of others. We must make exception for certain special cases in which no one is injured. (Vide Couvreur's "La Graine," and de Maupassant's "Mouche.")
The novelist loves to treat of tragic situations, often giving them a fatal ending to excite the feelings of his readers. We must avoid basing sexual ethics on such ideas. The average man, or even one whose nature is a little above the average, is rarely as passionate as the heroes in novels. He does not commit suicide for rejected love, but finds compensation in time. He can even overcome jealousy.
It is thus an exaggeration, depending partly on the suggestion and auto-suggestion of amorous intoxication, to require in the ethics of love the absolute fusion of the personality of two human beings, a mutual fusion of sentiments and ideas destined to last till death. This kind of morality reverts to dual egoism, and in no way represents the ideal of human happiness. However beautiful conjugal fidelity, its exaggeration is deplorable, when it only results in the idolatrous worship of a single being, living or dead, and regards the rest of the world with indifference, if not with hostility.
We have already shown that the altruistic sentiments of man are the direct or indirect[10] derivatives of the sexual appetite, and especially of sexual love. The true secret of sexual ethics consists, therefore, in a cult of altruism in the sexual domain. This cult should not waste itself in moral phrases, but show its strength by social deeds.
A sad proof of human weakness is given daily by certain forms of modern ethics which waste themselves in public conferences or in declamations in the press. This kind of morality is in accordance with pure egoism. Without social work, it is not true morality, whether this work be public or modestly hidden.