We’ve all heard it before: “If we allow gay marriage, next thing people will be trying to legalize polygamy!” Which statement will get one of two responses from pro-marriage-equality folks: “That’s ridiculous!” or “Uh… yeah?”
You may guess that I’m in the latter category, and you’d be right. But then the stereotypical protester will say, “And next thing they’ll allow a man to marry a dog, or an eight-year-old!” And then (if they didn’t already) the typical responder will cry “slippery slope fallacy!” But the protestor will point out that people like me are already going from “a man can marry a man” to “a man can marry a man and two women” and ask how fallacious that fallacy really is.
Well, I’ll tell you: totally fallacious. And that’s because there’s a big brick wall about halfway down the slippery slope. And on that wall, in bold capital letters, are the words “CONSENTING ADULTS.”
Consent is the watchword of modern sexual ethics. It’s the difference between BDSM and abuse. It’s the difference between polyamory and cheating. It’s the difference between rape and… sex. Anything two (or more) able, informed adults give consent to in private is generally considered okay. (“In private” is important because a couple going at it in the street are involving passersby in their sex life without their consent.)
There’s a little philosophical room around the question of who is able to give consent, but it’s generally understood that children, animals, and the severely mentally impaired (either permanently or temporarily, as by alcohol) are not. Likewise it’s understood that a large power differential, as between a boss and employee or a teacher and student, may obscure consent. But “consenting adults” remains the watchword, and all debates about the ethicality of any particular situation have to be conducted under those terms. Have both parties clearly consented? Are there any factors which might impair or nullify either’s ability to give consent? These are the questions that need to be asked.
It’s hard to imagine what other questions can sensibly be invoked. People who argue the gay marriage -> polygamy -> pedophilia -> bestiality slippery slope are usually correlating these four very different behaviors because all of them seem “unnatural.” But “natural” and “unnatural” are subjective and mostly meaningless categories. “That’s not natural” really just means “That makes me uncomfortable.” And I hope we can all agree that an individual’s sense of comfort or discomfort makes for a really lousy moral guide.
Someone might say, “But that goes against my religious code!” Fine, then don’t do that, and encourage your religious brethren not to do it either. But that has nothing to do with whether a thing should be legal or acceptable in the culture outside your religion. And if everybody in the world followed religious guidelines, that would still not be sufficient protection against sexual abuses. Some prophets are told by God to marry nine-year-olds, ya know. Laws exist to protect individuals from religion as much as they exist to protect individuals for religion.
The only other reasonable basis for argument, from a legal standpoint, is “Is this healthy for society as a whole?” And the follow-up, “If it’s not entirely healthy, is it unhealthy enough to warrant curtailing personal liberties?” Since the family is a social arrangement, it is fair to ask this when considering any particular kind of marriage. The question with gay marriage has been, “Is it healthy for a child to be raised by same-sex parents?” The preliminary results are in on that one, and the answer is yes. Whenever society takes up the question of polygamy, the same question will be asked, and I think that’s fair. With polygamy, there are additional questions raised, relating to things like citizenship and insurance benefits. But all these questions can and should be answered with hard evidence and studies, not on the basis of people’s gut sense of comfort or discomfort.
Also keep in mind the second part of the social-health question, “If unhealthy, is it unhealthy enough to warrant curtailing personal liberties?” Suppose study after study showed that children, in fact, do better when raised by same-sex parents, or polyamorous parents. (I can think of several reasons why either might be so.) How much better would it have to be before you’d support a ban on heterosexual monogamy? We’ve known for decades that children do better when raised by two parents rather than one, but no sane person suggests a law preventing single people from having children. We hold very highly the rights of heterosexual people to live, love, and create families as they see fit. In time, I hope that consenting adults of any number and gender are given the same level of respect.