Kira Cochrane rekons two in a marriage is enough

A future in which a man might marry his sister, his mother and his Labrador? Yikes! But realisticall

Blame it on Tom Hanks. (No, not for Forrest Gump. Come on, guys, that was years ago.) No, this time Hanks is in the frame to become an executive producer of the drama series Big Love, which has been running in the United States for a month or so, and causing quite a rumpus. About a polygamist family in Utah (one husband, three wives), this broadly sympathetic show has put group marriage under the spotlight at a time when a wave of polygamist activism is sweeping the nation, including a federal lawsuit that is challenging anti-polygamy legislation.

These events have left conservative commentators asplutter about how the, so far unsuccessful, campaign for gay marriage in the US is opening the floodgates for all sorts of relationships to be considered under the law. This "slippery slope" argument was first made by Senator Rick Santorum in 2003. "If the Supreme Court says that you have the right to consensual [gay] sex within your home," he said, "then you have the right to bigamy, you have the right to polygamy, you have the right to incest . . ."

This conflation of gay marriage with polygamy and incest naturally pisses off America's gay-rights activists. Conservative commentators justify their position by stating that marriage has historically involved two fundamental components: first, two people; second, two people of opposite sexes. Remove either of these, they suggest, and the entire structure collapses. It's a view that many in Britain take as well. Writing in her blog, the British columnist Melanie Phillips has said: "As some of us predicted, the next sexual frontier to be conquered after gay marriage is . . . polygamy . . . So now anything goes - and our society is steadily going, as a result. Polyandry, polyamory, polygamy, polymorphism - can paedophilia, necrophilia and bestiality be far behind?"

All of which makes for a very convenient and portentous argument against gay marriage, perfectly tuned to scare the horses and all other mammals besides. (A future in which a man might marry his sister, his mother and his Labrador! Yikes!) Realistically, though, it seems like baloney.

For the fact is that gay marriage, a marriage between two consenting and unrelated adults, is analogous with straight marriage in a way that polygamy (and all the other suggested options) can never be. The UK has taken this on board with the recent implementation of civil partnerships for gay couples. If, socially and legally, marriage is primarily an engine for cohesion, designed to create stable and healthy family units from which both partners are discouraged to stray, then clearly, it seems in society's best interests to allow gay marriage. On a personal level, too, with most people recognising that a gay identity is innate, it would be highly discriminatory not to.

When it comes to questions of discrimination, some polyamorists (people who openly have more than one lover, but are not married) are arguing that their need for more than one partner is as innate and discrete as a "gay" disposition, and should be recognised as such. But let's face it - this is going to take some proving. Most people in a long-term relationship have felt a strong need for another partner - a sudden, blinding attraction for a girl in a bar or a guy at the office - whether they pursue it or not. The sheer prevalence of this "disposition", this yearning for more sexual partners, would seem more a justification for abandoning marriage altogether than a case for extending its constructs.

Don't get me wrong: if people want to live communally, forming a long string of relationships, picking up new partners and discarding old ones, or remaining for many years in a stable collective of three or four or 27 people, that's entirely their call.

It would make no sense, however, to write this into law. Liberal polygamy is just too variable. What happens if one partner in a group of three decides to leave, for instance? Are the remaining two still married? And what if two of the three partners are happy with the set-up, but the other wants to invite more people into the marriage? Marriage is potentially rocky enough when there are two people involved, but the endless permutations of polygamy are impossible.

This probably explains why polygamy has usually taken a much more conservative form: what might be called the "harem" model (as seen in Big Love). The website for the US Christian polygamy organisation TruthBearer makes it very clear that "This is NOT about polyandry": God forbid that a woman should take more than one husband. Instead, the conservative/religious model of polygamy is a feudal system in which the husband is overlord. Rather than being in any way progressive, this set-up takes us back to a time when all notions of equality were moot.

Given the inherent differences, it is to be hoped that this conflation of gay marriage with polygamy will end in the US. To claim that there is an overlap or a "slippery slope" is entirely specious. The polyamorists will likely continue, separately, to try to convince us of their cause, and they are welcome to give it a go.

If they should ever succeed, after all, it could be one helluva wedding party.