Elise has posted her promised piece on polygamy, which is part of a series she has kindly named after me. At least, I hope she is intending to be kind.
She ends this way:
"I do not object to gay marriage. However, I do not consider those who do object to it to be stupid, ignorant, bigoted, shortsighted, ridiculous, not worthy of response, or crazy. Instead I respect their position, acknowledge the validity of their concerns, and couch my position in terms of my own preferences and my opinion that legalizing gay marriage will not undermine the role marriage plays - or should play - in holding society together. This leaves me free to oppose legalizing polygamy when the time comes. I realize full well that when I do argue against legalizing polygamy, I will be denounced as stupid, ignorant, bigoted, shortsighted, ridiculous, not worthy of response, or crazy. I’ll have to put up with that but I don’t plan to give anyone grounds to also denounce me as inconsistent."
I guess it's good to avoid inconsistency, exceptis excipiendis. I do not support "gay marriage," for reasons explored in great detail in the comments here, but which largely boil down to my sense that marriage is wrongly thought of as a contract, and rightly thought of as a kinship bond. The idea that any two people should be free to marry is part and parcel of the idea that marriage is just a contract between two individuals, which exists for their pleasure and convenience and can be dissolved for the same reasons. Only when we see marriage as the institution that it really is -- the formation of a kinship bond that unites bloodlines across generations -- can we correctly account for the duties arising from it that are owed to both previous and subsequent generations. These begin with not divorcing, but certainly include structuring marriage so that it has at least the theoretical potential of producing a subsequent generation.
So, I have never been a supporter of this concept called "gay marriage." However, one argument against it that I never found convincing was the slippery slope argument that gay marriage might lead to polygamy.
The problem wasn't that the argument might not be in some sense accurate, but that the argument was unprincipled. By this I mean that it did not have a grounding principle for marriage that could explain what the institution was, or what it was for. All it was doing was trying to use a less-popular change to undermine support for a more-popular change.
If marriage really is -- as Elise says -- just whatever we decide to call by that name, then there is no foundation for the institution at all. If it is, as I say it is, a kinship bond that unites bloodlines across generations, then polygamy at least preserves the core of the institution in a way that "gay marriage" does not and cannot. The slippery slope argument doesn't work, because "gay marriage" is already the bottom of the slope.
Which, I suppose, is reason for hope in a sense; once one has reached the bottom, at least things won't get worse.
I've been reading St. Thomas Aquinas on the subject, whose arguments are sometimes very good and sometimes quite dodgy; we'll take a look at his lengthy piece on the subject in a bit. Let's talk about Elise's ideas first.