IN 1997, two prominent conservative writers, David Frum and Andrew Sullivan, debated same-sex marriage for the online magazine Slate.

Frum defended what was then the consensus conservative (and consensus national) position. Redefining marriage to include same-sex couples, he argued, would explicitly sever the institution’s connection to the two interrelated realities, gender difference and procreation, that it had evolved to address. In so doing, it would replace a traditional view of matrimony with a broader, thinner, more adult-centric view, which would ultimately be less likely to bind parents to children, husbands to wives.

“Proponents of gay marriage can only get what they want,” Frum wrote, “by weakening Americans’ attachment to the traditional family even more than it has already been weakened,” and speeding the “process of social dissolution” that the 1960s and 1970s began.

Sullivan countered that the “process” Frum feared was simply an established fact. Heterosexuals had already severed marriage from procreation and permanence, and so there was no more reason to deny same-sex couples marriage licenses than to deny them to the infertile and elderly. Indeed, far from being radical, gay marriage was more likely to be stabilizing, “sending a message about matrimonial responsibility and mutual caring” to gays and straights alike.