TO WHAT extent does the debate over same-sex marriage resemble the debate over abortion? Both involve thorny, intersecting questions of religious freedom, personal liberty and sex. Both involve conflicting narratives and costs. The division between the two sides is wide, and like many debates fuelled by religious fervour; at times it risks becoming absolute. But not always: witness the conversion of Rob Portman, a conservative senator from Ohio, from gay-marriage opponent to supporter thanks to the coming-out of his son. Mr Portman came to realise that gay marriage represents not "a threat but a tribute to marriage, and a potential source of renewed strength for the institution." Indeed. But he also warns that change evolves slowly, and that it "should come about through democratic processes in the states. Judicial intervention from Washington would circumvent that process as it's moving in the direction of recognising marriage for same-sex couples. An expansive ruling would run the risk of deepening divisions rather than resolving them." That, of course, is a veiled reference to the Warren Court's decision in Roe v Wade in 1973. That ruling rather tendentiously found that women had a constitutional right to a first-trimester abortion. At the time, abortion-rights advocates celebrated, believing it would settle the long, divisive debate over abortion. As we know, it has not. Even Ruth Bader Ginsburg, a liberal Supreme Court justice and staunch advocate for women's rights, criticised the decision for "step[ping] boldly in front of the political process." Roe short-circuited a growing state-level trend toward liberalisation of abortion laws. It galvanised, perhaps even created, the pro-life movement. And as Ms Ginsburg says, "it seemed entirely to remove the ball from the legislators' court." Sometimes, she contends, this is necessary; in the 1950s southern states showed no movement toward ending segregation, which was plainly unconstitutional, and so the courts had to step in. But Mr Portman and Ms Ginsburg seem to agree that social change is best enacted through legislatures rather than courts.

Josh Barro takes a different view. He thinks that a strong Supreme Court decision in favour of same-sex marriage would save Republicans from a long, embarrassing and ultimately losing fight while also giving "Republican politicians a useful scapegoat to impotently shake their fists at." Today 30 states constitutionally ban same-sex marriage. A Supreme Court decision in favour of same-sex marriage would render those archaic and moot, like state bans on interracial marriage (which South Carolina and Alabama finally got around to removing in 1998 and 2000: 31 and 33 years after the Supreme Court invalidated them in Loving v Virginia). Mr Barro also points out that most civil-rights decisions (Brown, Lawrence) weaken rather than entrench social division.

So who is right: Mr Barro or Justice Ginsburg. Well, take a look at the arguments made by the same-sex marriage opponents profiled on Wednesday by Ashley Parker. They take Roe as an inspiration, an example of how one side can lose a decisive battle yet fight on in a long war. Caitlin Seery says, "When you de-link marriage from childbearing, you then have to increase the complexity of that relationship." I assume, then, that Ms Seery opposes not just same-sex marriage, but also marriages among heterosexuals past child-bearing age, and indeed heterosexual marriages that do not produce children. I eagerly await her proposed constitutional amendment requiring married couples to procreate. Ryan Anderson, a Heritage Fellow, makes a similar argument based on reproduction, which is fine, but why then does it not apply to non-procreative heterosexuals? He also frets that same-sex marriage "exclude[s] sexual complementarity"—the old argumentum ad genitalium, that gays' equipment doesn't fit right. Not to dwell too long on the bedroom, but I presume committed gay couples have found a way to be sexually complementary (and probably sexually complimentary too!). This argument requires opposing sodomy for heterosexuals too, which Mr Anderson does not do. Apparently non procreative sex is only wrong when gays do it.

Finally, Joseph Backholm complains of same-sex supporters "fram[ing] this as a vote for gay people to be happy." Well, yes. It is a vote for gay people to have the same defining, challenging, fulfilling, frustrating, enriching, beautiful and complete marital relationships that the rest of us have. And that is a fundamental difference between same-sex marriage and abortion. Everybody loves a wedding; nobody likes an abortion. Supporters of abortion rights simply believe that safe, legal and rare is better than unsafe, illegal and rare. The better analogy for same-sex marriage is, of course, interracial marriage. Some people still don't like it. Fine. They can marry within their own race and grumble impotently at the TV. But what they can't do is tell anyone else who to love and who to marry. Same-sex marriage supporters frame the case as a vote for gay people to be happy because that is precisely what it is.

(Photo credit: AFP)