According to the definition given above, we may classify every sexual desire as ethically positive if it is of benefit to individuals, to society, and especially to the race (that is, to posterity); as ethically negative if it does injury to any or all of these; and as ethically indifferent if it neither does injury nor is of any service. At the same time we must observe the ethical gradation: (1) the race, (2) society, (3) the more intimate surroundings or family, and (4) the individual self.
When we come to examine the concrete cases more closely we find that the circumstances attendant upon the gratification of the sexual desire, and the consequences of this gratification, lead to conflicts with morality far more frequently than does the sexual act itself.
In the first place even the normal reproduction of human beings may become immoral, in that it may do injury to the race or to individuals. Malthus pointed out this fact. Habitable space upon the earth is limited, while, on the other hand, the procreative capacity of mankind is unlimited. If unlimited reproduction is permitted, it is possible that the existing space may be insufficient to meet the needs of the enormous multitudes of men which must result. The latter may then fall victims to famine and distress, as in the case of the Chinese, or the rabbits of Australia; and only disease, starvation, or slaughter can bring about a return to the normal condition. It must be obvious to every unbiassed person that this is not moral. And as there are harmless methods of regulating the number of births and to some extent the quality of the offspring, the just and proper use of these methods must be described as ethically positive. Everything is moral which makes for the happiness and well-being of society; everything immoral which prejudices or endangers it.
There can, however, be too few people in the world; and there is everywhere a great dearth of men and women wholly sound in mind and body, light-hearted, unselfish, industrious, persevering, intelligent, able and yet well-intentioned, peaceable, and honest.
On the other hand, we have a monstrous superabundance of feeble, sickly, mentally perverted, criminally disposed, idle, treacherous, vain, crafty, covetous, passionate, capricious, and untrustworthy individuals, whose claims upon others are inexhaustible, while their own services to society are either valueless or actually harmful.
While the first-mentioned class produce far more than they consume, it is appalling to think of the vast store of human energy and human life which goes to waste in sick-rooms, lunatic asylums, hospitals, and prisons. And if we look more closely we find outside these institutions, and under no restraint, a still vaster army of human sharks, who prey physically and mentally upon society, and are a burden upon the industrious community. The greater number of these useless pests owe their faults to an hereditarily defective constitution of the protoplasmic germs which brought them into being; and therefore a sound system of racial ethics demands rational selection in breeding.
Equally destructive, however, are external conditions and habits of life, such as the use of alcohol, resulting as they do in paralysis of energy, confusion of the mind, and degeneration of the cells (blastophthory).
The libido sexualis, or sexual desire in mankind is infinitely stronger than is necessary for the reproduction of the race. Man has no breeding season; he is always ready for sexual intercourse. Although the number of women in the aggregate only slightly exceeds that of men, the male has usually an instinctive inclination to polygamy. Luther accurately estimated the normal requirements of a healthy man in the prime of life at on the average two to three sexual connections in each week; and yet this is far in excess of what is necessary for the procreation of children in a monogamous marriage. It is, moreover, well known that a man can even considerably exceed the above number without injury to his health, and there are women whose needs in this respect are actually greater than those of men.
It therefore follows that the widespread artificial excitement of the sexual desire from motives of sensuality is harmful from the standpoint both of ethics and of social hygiene.