A while ago, I responded to the legislation on gay marriage with the question of what in liberal theory prevents consensual adult incest and bestiality. The question seemed to me to be rhetorical, but it apparently was not, as readers’ letters indicate. A Google search for “consensual adult incest” produces 13,000 exact matches, mostly with approving opinions.

Once we accept the right of individuals to any behavior in the privacy of their homes as long as it is not harmful to others, there is no conceivable reason to ban consensual adult incest. Two arguments are often made to the contrary. One is the possibility of genetic damage. Such damage, however, only appears in cases of long-term inbreeding among small groups. That is, if a small, completely isolated village allows marriage of close relatives, in hundreds of years genetic diseases would spread there. The single-generation effects of incestuous propagation are negligible; studies of married cousins show genetic risks increasing by less than 1 percent. If societies have a legitimate interest in reducing genetic risks, then it is only logical to step into eugenics, or at the very least sterilize people with a genetic predisposition to dangerous illnesses. Genetic predisposition to breast cancer, for example, accounts for up to 60 percent of occurrences, which makes the genetic risk factor of  single-generation incest (below 1 percent) negligible.

It is also dubious whether societies have a legitimate interest in purifying their genetic pool. There is a small step between resisting negative genetic developments and seeking out positive ones, mating blond women with six-foot men. Societies allow parents to choose any medical insurance for their children, and don’t even punish the lack of insurance as criminal negligence; presumably, such societies can leave it to parents to care about their future childrens’ genetics. Prospective spouses can always undergo pre-marital genetic tests, and can refuse partners with bad genetics; in such a way, private actions filter out the high-risks of incestuous relations and their offspring.

There is a large sphere of non-procreative incest, whether as homosexuality or protected sex. There is procreative non-genetic incest, such as between in-laws. Genetic concerns are irrelevant in such cases. So the courts advanced the idea of protecting the nuclear family. The wording is very vague: there is not even any  commonly accepted definition of a nuclear family. Homosexuals argue that their couples are nuclear families; divorceés with others’ children consider themselves a family; separated spouses are a family; and so on.

What interest in nuclear family do societies have that allow homosexual marriage? The rampant divorce rate shows that childbirth does not strictly correlate to the strength of families. Besides, economically attractive societies can always achieve any desired population growth through immigration. Sparta was reportedly strong without a nuclear family. Whatever the case, internal migration and hedonism made the nuclear family almost extinct in the West: children live far from their parents, speak to grandparents a few times a year, marry late, and divorce often.

If the nuclear family is a concern, why ban polygamy? Mohammed, the first Muslim, remarked correctly that it is legitimate to marry several women as long as you can be fair to all of them. Judaism has that concept regarding concubines (Exodus 21:10). Polygamy was formally banned for Jews only a thousand years ago by an obscure rabbinical decree—which has expired. Developed consumerist societies allow common men enough resources to treat several wives fairly in economical terms.

All sages concur that familial connections cease in the afterlife, so there is no transcendent value in them. Polygamy is also just: the Bible commands a man to stick with the wife of his youth. The idea is not to send her away when she becomes old and ugly. This obligation is most straightforwardly kept by acquiring another wife. Polygamy is the only way to realize an important commandment of Levirate marriage, the one for artful violation of which Onan was punished with death (and not for masturbating). Only in a polygamous society could the Torah demand that a menstruating woman should not touch anything or anyone; other wives cared for her children.

Polygamy is a standard in many societies, and has persisted for ages; it cannot be identified as an antisocial factor. In fact, the West practices polygamy in the forms of divorce/re-marriage and extramarital relations. Hugh Hefner has three de facto wives; why should be two de jure wives banned to others? What, indeed, is the moral or even legal difference in the common-law countries between having two wives and having a wife and a mistress? Child support obligations apply to both relationships, and all children, legitimate or not, are entitled to inheritance. Moreover, societies don’t recognize childrens’ right to a parental environment: divorces are easily gotten, and in extreme cases, some Israeli kibbutzim even raise the children collectively, in dormitories.

The polygamy in question is a consensual adult behavior: if a woman wants to be a second wife, what in moral theory allows the state to ban that? Polygamy of some women improves the marital prospects of others, as women become scarcer and therefore more valuable. And the other way around, many males would be happy to have the opportunity to marry a female porn star simultaneously; nothing in the secular worldview substantiates banning such practice. For historical reasons, Western societies are unlikely to become overwhelmingly polygamous, and even 10-20 percent of adults entering polygamous unions won’t change a society’s demographics too much. The divorce rate and reduction of birth rate induced by social security and consumerism affect demographics to a much greater extent.

Polygamy is a powerful evolutionary device which rids society of inefficient males. In polygamous society, some males are deprived of wives, and the males who are neither smart, nor strong, nor good-looking die out. In another scenario, they get foreign wives from undeveloped countries. As they fish for some of the best women there, their own genetic deficiencies are mitigated.
For Israel, legalizing polygamy would have important political consequences: a return to normative Judaism and an end to subsidies to Arab families. Now an Israeli Arab who has four wives (or more, if he is a Bedouin) can only register one of them. The rest are considered single mothers and receive subsidies from the Jewish state. Legalizing polygamy would end those subsidies.

The only argument against bestiality is animal rights. So a man can kill a sheep, flay it, and eat it—but not have sex with it? Perhaps it even enjoys sex. This silly argument is still weaker for female bestiality; the very fact of the animal’s orgasm proves that the donkey or whatever enjoys the intercourse.

Leftists insist on keeping the law rational, and that is possible most of the time. Sometimes, however, the law deals with non-rational issues, and therefore cannot be rational. Analysis can help us determine the maximum speed on highways or the necessary level of taxation, but even in such straightforward cases the conclusions are debatable. Communist societies failed at planning economies, but on the issue of marriage, states attempt to regulate morals. The governments can take several approaches. One, go liberal, remove the ban on incest, and don’t forget to introduce a ban on hate speech toward homosexuals.

Two, go libertarian: end the state’s regulation of moral matters, but allow the hate speech. Thus, anyone could marry a sheep, but everyone can call him a pervert and suggest ostracizing him. The liberal policy can never be consistent, as societies would always have to enforce some moral norms on behalf of the vast majority (but not all) of their citizens. Governments can, for example, allow public nudity, but it is unlikely that they would allow public urination.

Three, go republican. Some values are non-negotiable and cannot be repealed by a democratic majority. The law, for example, bans voluntary slavery: a person cannot sell himself into slavery, though undoubtedly millions of Africans would be happy to sell themselves to Iowa farmers. The law, however, rejects voluntary slavery even if 99 percent of the population would support it. The prohibition of voluntary slavery is exceedingly dubious, but it is nevertheless enshrined in the law. Even so, basic moral norms deserve republican protection instead of being submitted to democratic decision-making.

Four, go religious. The Bible recognizes the immense attraction of incestuous and homosexual relationships. People are naturally attracted to their likeness, whether genetic kin or the same sex. If such relations were not attractive, the numerous biblical prohibitions against them would be unnecessary. Astonishingly, the commandment against incest says, “And if a man would take his sister… it is hesed” (Leviticus 20:17). The common translation of hesed as shame is nonsensical. The word universally means loving-kindness with an etymological connotation of a zealous, protective relationship.
The prohibition alludes to Song of Songs, in which an extremely agitated King Solomon calls the girl, “my sister, my bride.” Before the kabbalah reinterpreted Song of Songs as an ode to God, rabbis were skeptical about the text to the point of refusing to include it in the canon. Naturally, “Solomon’s love” was enshrined in the prohibitive commandment.

The message is the following. The Torah guards us against excesses, leading us to, in Rambam’s words, the middle way. When people take the path of excess—any excess—they tend to follow it to the end. Indeed, once a deviation from the middle way is accepted as a norm, nothing logically precludes people from running after any goal, neglecting other goals in the process. One such neglected goal—the major goal—is the divine service. Once a person runs into sexual excesses, he is extremely unlikely to remain religious.

And so the Torah warns us that the bond between brother and sister is an extreme one; it is zealous loving-kindness. The intensity of feeling is such that it would surely distract them both from the proper, moral life.

Extreme movements break any mechanical system fast. Extreme behavior is similarly dangerous to societies.