A big thanks to the commenter Thursday for posting this long essay about same-sex marriage by libertarian Megan McArdle, dating to a few years back, when she was writing as “Jane Galt.” Let me be clear: in the piece, McArdle explicitly takes no position for or against SSM (I don’t know where she stands on the issue today). She does a great job, though, of presenting a key conservative objection to SSM: that a social institution like marriage should not be dismantled so cavalierly. I will excerpt it here, but you really have to read the whole thing. We join the essay after McArdle has cited three examples of laws torn down for the sake of social reform, the result being disaster:

Three laws. Three well-meaning reformers who were genuinely, sincerely incapable of imagining that their changes would wreak such institutional havoc. Three sets of utterly logical and convincing, and wrong arguments about how people would behave after a major change.

So what does this mean? That we shouldn’t enact gay marriage because of some sort of social Precautionary Principle

No. I have no such grand advice.

My only request is that people try to be a leeetle more humble about their ability to imagine the subtle results of big policy changes. The argument that gay marriage will not change the institution of marriage because you can’t imagine it changing your personal reaction is pretty arrogant. It imagines, first of all, that your behavior is a guide for the behavior of everyone else in society, when in fact, as you may have noticed, all sorts of different people react to all sorts of different things in all sorts of different ways, which is why we have to have elections and stuff. And second, the unwavering belief that the only reason that marriage, always and everywhere, is a male-female institution (I exclude rare ritual behaviors), is just some sort of bizarre historical coincidence, and that you know better, needs examining. If you think you know why marriage is male-female, and why that’s either outdated because of all the ways in which reproduction has lately changed, or was a bad reason to start with, then you are in a good place to advocate reform. If you think that marriage is just that way because our ancestors were all a bunch of repressed bastards with dark Freudian complexes that made them homophobic bigots, I’m a little leery of letting you muck around with it.

Is this post going to convince anyone? I doubt it; everyone but me seems to already know all the answers, so why listen to such a hedging, doubting bore? I myself am trying to draw a very fine line between being humble about making big changes to big social institutions, and telling people (which I am not trying to do) that they can’t make those changes because other people have been wrong in the past. In the end, our judgment is all we have; everyone will have to rely on their judgment of whether gay marriage is, on net, a good or a bad idea. All I’m asking for is for people to think more deeply than a quick consultation of their imaginations to make that decision. I realize that this probably falls on the side of supporting the anti-gay-marriage forces, and I’m sorry, but I can’t help that. This humility is what I want from liberals when approaching market changes; now I’m asking it from my side too, in approaching social ones. I think the approach is consistent, if not exactly popular.

As I said, read the whole thing.  McArdle was not then and is not now a social conservative, for the record. She was just trying to be fair, and wise.