It always comes back to one essential truth: People want to have sex with monkeys.
The slippery slope argument has trailed gay marriage like a desperate bridesmaid. Gay marriage opponents sooner or later (usually sooner) make the claim that governmental approval of same-sex nuptials will open the door to marriages among multiple partners, between close family members, between adults and children, between humans and animals, etc. Proponents alternately refuse to engage these arguments or, worse, sniff at the alternatives.
"[The ruling by the Massachusetts Supreme Court that banning same-sex marriage creates a second-class status of relationship] is not accurate," says Matthew D. Staver, an attorney with Florida-based Liberty Counsel, which is suing San Francisco mayor Gavin Newsom over his decision to issue same-sex marriage licenses. "It creates no different status than what we've said about incestuous or polygamous marriage. There is a whole range of age differences that we don't recognize in marriage. We obviously make distinctions; the question is whether you think there's a rational basis for such a distinction. I think there is clearly a rational basis for not privileging same-sex marriage in the same way you would marriage between a man and a woman."
Supporters of gay marriage ignore such arguments at their own risk. The various legal and legislative contests at work these days can't be treated in detail in this article: President Bush's proposal of a marriage amendment to the U.S. Constitution seems unlikely to attract the necessary supermajorities, and history has not been kind to attempts to take the Constitution beyond its functions as a governmental framework and into social and cultural prescription. Whether Newsom is violating California's Proposition 22 or (as he argues) upholding the state's equal protection requirements will be decided in court later this month. Meanwhile, our ongoing national crash course in marriage law provides little guidance to this new domestic category.
But the slippery slope argument is at least worth considering. It seems unavoidable that widespread acceptance of gay marriage will in fact create a push for recognition of alternate domestic arrangements—those named above as well as others we haven't thought of yet.
What gay marriage opponents (or, if you prefer, defenders of traditional marriage) don't acknowledge is that many of these challenges would go nowhere. Marriages to children or animals will remain out of bounds on the basis of statutory rape, consent, and animal cruelty laws that have nothing to do with marriage. In other cases, lack of demand would make state intervention unnecessary. There may still be a powerful incest urge in the world's remaining royal families, but here in America, where we bend the knee to no man, E.O. Wilson has persuasively argued that rejection of incest is an essential trait; it would hardly require government intervention to prevent brothers and sisters from marrying each other in large numbers.
Randy Thomasson, executive director of Campaign for California Families (a plaintiff in the suit against Newsom), disagrees. "Historically, issues of age and number of partners have been secondary to the requirement that a marriage consist of a man and a woman," he says. "This is where the libertarian argument for non-intervention breaks down. If consenting adults is the rule of the day, then three or four people who want to marry each other would become normal in America."
And what if it did? Thomasson claims that such changes would "do away with the foundations of society," but this is debatable: Whatever complaints we may have with Islamic civilization, it certainly was not undermined by widespread polygamy. There is no credible basis for proscriptions on such behavior between consenting adults; it was improper for the U.S. government to pressure Mormons into changing their domestic behavior, and unfortunate that the LDS Church capitulated to this unconstitutional infringement.
But conservatives are right: Opening up the debate to alternative domestic arrangements like these would have an impact, in ways that can't be easily dismissed as private concerns. Marriage entails serious rights and benefits—more than a few of which involve coercion of some third party. City and state governments around the country already require employers to extend health care and other benefits to employees' spouses. It is arguably unreasonable to expect an employer who abhors homosexual behavior to subsidize a same-sex marriage. It would be financially ruinous to make a boss insure the seven husbands of one of his employees. The Internet is already brimming with offers of Asian brides in search of green-card husbands; how many sham marriages would the U.S. Citizenship and Immigration Service have to sift through once an American man could marry thirty Filipinas? What tax benefits will apply to a plural marriage? How can the authorities turn informants among a criminal gang whose members are all married to each other and thus have immunity from testifying in court?
Many of these examples are too unlikely or absurd to merit consideration. But an expansion of marriage opportunities would raise valuable dilemmas, the solutions to which may well involve devolution of government interference in the private sector. If it's unreasonable to expect a boss to insure multiple spouses, why is it reasonable when we force her to insure just one? Single people already subsidize their married co-workers and fellow taxpayers in numerous ways; perhaps it's worth reconsidering the social engineering arguments that created this situation. Maybe it's even worth taking another look at the "family reunification" goals of the 1965 Immigration Act. Up until now, we've been content with a vast range of marriage-related governmental intrusions. Gay marriage calls many of them into question. I have no love for Gavin Newsom—who as a supervisor ignored my repeated requests to fix a dangerously defective traffic light on my corner—but he may inadvertently be steering us toward a truly private definition of marriage.
So far, proponents of same-sex marriage have been content to make mutually exclusive arguments—that gay marriage is no big deal and that it is vitally important. They should be more courageous in their assertions: Gay marriage could well destroy the civic institution of marriage that has been defined by more than a century of governmental tinkering. That's the best argument for it I've heard yet.