That question applies in the US — and possibly in some surprising places elsewhere. Let’s start in the US, where the march of court opinion has moved steadily over the last decade from the inherent right to sexual privacy and choice in Lawrence v Texas to the mandate for government recognition of partnership choices in the emergence of same-sex marriage as an equal-treatment issue. During the latter period of that arc, opponents of SSM warned that the same arguments deployed in that effort could be made to force recognition of polygamist relationships as marriages too, which SSM advocates hotly denied. Now that the courts have made a near-sweep on same-sex marriage, Sally Kohn wonders why polygamy should be any different:

Back in the early days of the lesbian, gay, bisexual and transgender movement’s push for marriage equality, this slippery slope to polygamy was pragmatically taboo. After all, arguments about gay marriage leading to polygamy were lobbed almost entirely with the purpose of derailing the gay rights agenda. And there was also something inherently offensive about making the connection, along the same lines of suggesting that gay marriage would lead to people marrying goats. …

[P]olygamy, as it generally is practiced in the United States, is a predominantly heterosexual enterprise—like heterosexuality (or the male ideal of heterosexuality) on steroids. After all, while the percentage of married women who have affairs has risen in recent decades, married men still do most of the cheating. Conservatives concerned about the high rate of divorce in America should stop blaming gay marriage but instead heterosexual infidelity—a prime culprit in 55 percent of divorces.

If couples want to bring cheating out of the deceitful shadows and instead incorporate it openly into their relationship—plus have more hands on deck for kids and more earners in the household in a tough economy—who are we to judge?  

Kohn argues that the push toward polygamy doesn’t come directly from same-sex marriage, but “a general opening up of options,” which is true on one level, but somewhat dishonest. The “opening up of options” springs from disconnecting marriage from its traditional definition of one man, one woman relationships. That was what “open[ed] up the options,” from which springs any number of definitions — which has the effect of making marriage essentially meaningless, except as a revenue source for local governments. That is, in fact, what opponents of SSM argued all along, as Kohn concedes.

Furthermore, it’s not really a question of judgment but of government approval. Kohn mixes this up with getting “support” from government:

There are interesting arguments to be made for legalizing polygamy, from protecting children from secretive non-consensual multiple-marriage situations to how being “feminist” actually means not protecting women from these marriages but letting them choose for themselves. …

But I do have a soft spot for allowing consenting adults to make their own decisions, and to be supported by their government in doing so, not constrained.

Over the last few decades, and certainly since Lawrence, there were no laws preventing consenting adults to cohabitate in any particular fashion they chose, except for consanguinity issues (incest). Those adults had options for formalizing their relationships in private contracts, which the government could then enforce when necessary. That was actual choice, rather than a demand for government recognition and societal approval. Kohn wants the latter, based on the fact that we’ve already disconnected the definition of marriage from its basis in protecting the core model of family life and ensuring parental responsibility for offspring, especially for fathers of children. Again, this is the slippery slope that those opposed to redefining marriage have warned was approaching all along. (It’s also the reason that some of us argued that the proper response was to get government out of the marriage business altogether.)

It’s not the only slippery slope related to polygamy, either. The Vatican will hold its much-anticipated Synod on the Family next month, after having bishops around the world survey their flocks on the challenges of modern family life. One of those challenges is polygamy — not in the US but in Africa, where the Catholic Church has become more and more isolated in its opposition to the practice. Any retreat on divorce and remarriage might undermine their attempts in Africa to push back against polygamy, John Allen writes for Crux (via Fr. Kenneth Allen):

In 1987, the Fifth General Assembly of the All-Africa Conference of Churches, a Protestant ecumenical body, concluded that “the rather harsh attitude of the Church has been a painful but real cause of disintegration of some otherwise stable marriages and families.” In 1988, the Lambeth Conference of the Anglican Communion decided to admit polygamists under certain circumstances, in response to pressure from bishops in Kenya and Uganda.

Catholicism, however, has held the line. Speaking to a Black Catholic Congress in the United States in July 2007, Cardinal John Onaiyekan of Abuja, Nigeria, said that on polygamy, “the Catholic Church is particularly firm and consistent, giving no room whatsoever for doubts and exceptions.”

The church’s tough stance has been shaped not only by defense of tradition, but also impressions that polygamy discriminates against women. In the late 1990s, a survey of African Catholic theology cited 23 female African Catholic theologians who argued that since mutuality and equality are Biblical ideals, Scripture should not be used to justify polygamous marriage. …

When cardinals from around the world met in Rome last February to set the table for the October synod on the family, some prelates from non-Western cultures hinted that polygamy may drive them to oppose any change in the ban on divorced and remarried Catholics receiving the sacraments.

Their argument went like this: The Catholic Church has been telling people in polygamous marriages that they have to change because marriage means one man and one woman, for life. If the Church softens that teaching for the divorced and remarried, it might face pressure to cut a deal for polygamists, too. …

“They’ve been telling people that if you come into the church, you’ve got to choose one wife,” DiNardo said. “If you suddenly change that, couldn’t [people in polygamous marriages] say, ‘Why can’t you give me a break, too?’ ”

That won’t be the only way in which the Synod will drive the debate over family issues in the West, but it may be one of the more surprising twists. With the fastest growth in the Church coming in Africa, this will present a particular challenge on consistency about the definition of marriage and its model of equality and commitment, and that could have a profound impact on how the debate turns in the US as well.