Bad Reasoning in the Same-Sex Marriage Debate, Episode I:
The Polygamy Objection and Responses Thereto

I.
I saw the following on C-Span several weeks ago (not verbatim):

Guy defending same-sex marriage (SSM):
“SSM should be legal because same-sex couples deserve the same rights as heterosexual couples.”

C-Span guy:
“So doesn’t that mean that polygamous marriage should be legal as well?”

Guy defending SSM:
“No. Polygamous people already have the same rights as everyone else. Just like non-polygamous people, they have the right to marry—they can enter into a two-person marriage. So there is no asymmetry in rights.”

II.
Whatever the merits of the polygamy objection against legalizing SSM, this response to the objection won’t work--especially for the defender of legalizing SSM. If this response worked, then the following anti-SSM argument would work (I’ve actually heard people make this argument, in fact):

“Homosexuals already have the same rights as heterosexuals. Both heterosexuals and homosexuals are free to marry someone of the opposite sex. So there is no asymmetry in rights.”

But this symmetry isn’t the relevant one. A heterosexual can (insert obvious qualifications here) marry the person she or he loves and wants to marry. If homosexuals cannot do likewise, then they are not equal before the law in the relevant respect. So this objection to legalizing SSM fails.

But if this objection to legalizing SSM fails, then the analogous response to the polygamy objection against legalizing SSM fails, since it makes an analogous error.

III.
But it isn’t clear how strong the polygamy objection against legalizing SSM is, so it isn’t clear how important it is to deflect it. For one thing, it isn’t clear that polygamy should be illegal, so, from a theoretical perspective, it isn’t clear that we should count the polygamy objection as an objection to legalizing SSM instead of as perfectly good argument for legalizing polygamy. From a pragmatic, political perspective, however, if legalizing SSM entails legalizing polygamy, then that’s pretty much the end of SSM; the American public is not going to stand for legalizing polygamy. (Are they?)

And, of course, it isn’t clear that legalizing SSM does mean that we must legalize polygamy as well. But some justifications for legalizing SSM do entail that polygamy should be legal. For example, one rationale for legalizing SSM goes like this:

People should be able to marry whomever they love.

But if that is true, then polygamy should be legal, since it is possible to love more than one person at a time. (And, of course, it isn't clear that we can/should make loving someone a requirement for being married to them, anyway. Talk about a principle that's a threat to the institution of marriage!) One might advocate this principle instead:

Everyone should be able to marry someone whom he or she loves.

That is, everyone should be able to marry at least one person that she or he loves. Given that some people love (in the romantic sense, of course) only people of the same sex, this principle entails that SSM should be legal. And, while it does not entail that polygamy should be illegal, it would permit us to make it illegal. But (aside from the fact that it yields the politically expedient result) why think that the latter principle is superior to the former one? This is almost equivalent to the question 'should polygamy be legal?', so fiddling around with the principles in this way doesn't really gain us any ground.

IV.
Liberals have a tendency to treat the polygamy objection contemptuously, but that’s a mistake. Unless I’m missing something, it’s a serious objection and should be treated as such.