Nature could not suddenly stop a man’s secretion of semen, but here, as in every case of mortification and decay, a gradual deterioration had to precede it. But procreation during this deterioration would bring into the world human beings who would be weak, dull, sickly, wretched, and short-lived.
In so important a matter, nature could not risk either of these expedients. There was then nothing left for her but to choose the lesser of two evils. But for this purpose she had to make use here in her own interests of her favourite instrument, instinct.
Nature knows only the physical, not the moral; in fact, there is even a decided antagonism between her and morality.
Now it is true that pederasty is detrimental to those youths who have been seduced into practising it, yet not so much so that it would not be the lesser of two evils. Nature accordingly chooses this, in order to avoid by a wide margin the far greater evil, depravation of the species, and so to avert a lasting and growing misfortune.
Accordingly, in consequence of her own laws, nature was hard pressed, and resorted to a makeshift, a stratagem, by a perversion of the instinct. In fact, it might be said that she built herself an asses’ bridge, in order, as explained above, to escape from the greater of two evils. Thus she has in view the important object of preventing miserable and wretched offspring which might gradually deprave the whole species; and, as we have seen, she has no scruples in the choice of means. For in both cases she resorts to what is bad in order to avoid what is worse; thus she leads the sexual impulse astray, in order to frustrate its most pernicious consequences.
From the World as Will and Representation
