As the Ricochet editors mentioned, tomorrow Encounter Books releases my new book, co-authored with Sherif Girgis and Robert P. George, What Is Marriage? Man and Woman: A Defense. So while blogging at Ricochet this week, I thought I’d explore some of the issues raised by the book—and recent events, thanks to the Supreme Court. Today I’d like to situate the debate over the definition of marriage within its proper context.

Some people wonder why conservatives choose to focus exclusively on same-sex marriage. The answer is simple: We don’t. First, conservatives always did—and still do—make other social and political efforts to strengthen the marriage culture. The push for same-sex marriage was brought to us. Second, now that this is the live debate, we can’t ignore it, for its outcome will have wider effects on the marriage culture that really is our main concern.

Long before there was a debate about same-sex marriage, there was a debate about marriage. It launched a “marriage movement,” to explain why marriage was good for the men and women who were faithful to its demands, and for the children they reared.

Articles in mainstream magazines such as Barbara Dafoe Whitehead’s 1993 cover story for The Atlantic, “Dan Quayle was Right,” documented how family fragmentation was wreaking havoc on society. In 1996 Mike and Harriet McManus launched Marriage Savers to combat marital breakdown, and in 2001 Wade Horn championed the Healthy Marriage Initiative for the Bush Administration. Their targets were high divorce rates and the rising birthrate for unmarried women. From pre-Cana programs to various fatherhood initiatives, examples could be multiplied ad nauseam.

Same-sex relationships weren’t on anyone’s radar. (It may be hard to remember, but until just recently same-sex marriage was inconceivable to almost everyone.) The marriage movement leaders’ concern, like that of today’s leading conservative scholars and activists, was much broader.

So it’s not surprising that the leading opponent of redefining marriage today, Maggie Gallagher, was active throughout the ’80s and ’90s in this marriage movement. She wrote a book in the late ‘80s on how the sexual revolution was “killing family, marriage and sex” and “what we [could] do about it;” in a 2000 book she made “the case for marriage,” showing the many ways that marriage is better for couples than cohabitation.

The question of whether to redefine marriage to include same-sex relationships didn’t take center stage until 2003, when the Massachusetts Supreme Court claimed to find a constitutional right to it. Those who had been leading the marriage movement for decades had to ask themselves: Would recognizing same-sex relationships as marriages strengthen the marriage culture, or weaken it?

They saw that redefining marriage to include same-sex relationships was not ultimately about expanding the pool of people eligible to marry. Redefining marriage was about cementing a new idea of marriage in the law—an idea whose baleful effects they had spent years fighting. That idea—that romantic-emotional union is all that makes a marriage—couldn’t explain or support the stabilizing norms that make marriage fitting for family life. It could only undermine those norms.

Indeed, that undermining already had begun.  Disastrous policies like “no-fault” divorce, too, were motivated by the idea that a marriage is made by romantic attachment and satisfaction—and comes undone when these fade.

Same-sex marriage would require a more formal and final redefinition of marriage as simple romantic companionship, obliterating the meaning the marriage movement had sought to restore to the institution.