Recent closing statements in the landmark Proposition 8 trial offered a good recap of the best arguments on each side of the same-sex marriage debate. For the opposition, possibly the strongest is the claim that children need a mother and a father, and that marriage is the institution that ties heterosexual sex to childbirth and parenting.

Clearly, that's one thing that marriage does, but it can't be the only purpose of the institution. If it were, we wouldn't let 80-year-olds get married, and if you've had a hysterectomy, then forget it. To complicate matters, gays and lesbians also raise children, and an institution that ties them to their kids, and that empowers them to raise their children responsibly, seems like a reasonable addition to the law.

Despite our intuitions, the social science comparing gay and lesbian families to similarly situated traditional families has had a hard time finding significant differences. That is, a child will likely have similar life prospects in the one or the other, once we control for incomes, parents' education, divorces, and the other usual suspects.

This research is still in its infancy, and both sides of the debate have been tempted to take shortcuts and jump to unwarranted conclusions. No one should be misled, for example, by a recent study of lesbian parents in which they self-report that they're doing just fine, thankyouverymuch. And no one should be fooled by a counter-study now being organized by the Ruth Institute, a conservative antifeminist group, in which self-selected straight women are asked to tell the world how great it is to have a dad in the house. (Next up: puppies are cute, and ice cream is yummy.)

However, one fairly safe preliminary finding is that if gay and lesbian couples were significantly worse as parents, we'd know it by now: An estimated 65,000 adopted children and 14,100 foster children now live with gay or lesbian parents. Gays and lesbians have also raised millions of their own biological children. If something were going seriously wrong here, we'd know. There could still be some differences. There probably are. But these differences probably aren't very large, and they pale before the prospect of a child never having a stable home at all.

I don't mean to put down moms or dads. It's great that people of both sexes usually take childrearing seriously. They should. The traditional family is great. It's a slur to say that gays and lesbians hate the traditional family. Most of us grew up in traditional families, after all, and we still love our parents and siblings, and they usually love us. What we don't love, though, is the way that the traditional family is used as a weapon to attack our own, less-traditional families.

All of this brings up a strange inconsistency to the opponents of same-sex marriage. Their ends -- every child gets a mom and a dad -- are strangely mismatched to their means -- prohibit same-sex marriage. It's sort of like banning bad moustaches to stop pornography. Perhaps there's some vague association, but that's about it.

Same-sex marriage isn't nearly the root of the problem, and we all know it. If it's really so important that every child gets a mom and a dad, then there is an obvious policy solution: prohibit divorce after childbirth. Of course, divorced parents are numerous and politically powerful, and it's always easier to scapegoat a minority.