But the traditional view of marriage pretty much requires one group of Americans to have legally recognized marriages (straights) and one not (gays and lesbians). One group of people have one set of rights, and another group of people doesn't have them. Our devotion to a traditional definition of marriage—that goes back to prehistory—runs afoul of our notion of equal justice under the law.

Unsurprisingly, some Christians and conservatives are not terribly interested in fighting a political battle on those terms and are shifting their focus elsewhere; others reconsider whether government should legally recognize marriages at all.

It is worth noting, of course, that the pro-gay-marriage argument has its own contradictions. One of the fundamental justifications often revolves around privacy, or the idea that "the government has no business regulating what goes on in our bedrooms." But obviously, these relationships are not exclusive to bedrooms. If they were, most straight Americans would never notice them. The question is whether a gay man or lesbian woman can live their lives in the public sphere with their same-sex married partners present, as widely and unremarkably as heterosexual married couples do.

Even the very language used in the debate is slippery, with homosexuality often described as a "sexual preference." But everyone has sexual preferences. A partner of the same sex is a sexual preference; so is black lingerie. Yet (to the best of my knowledge), homosexuals are uniquely expected to have their whole lives and worldview defined by that sexual preference. There are no black lingerie neighborhoods (alas) or High Heeled Boots Political Action Committees; Democrat Party leaders do not accuse GOP candidates of deep-seated red-lipstick-ophobia. (Well, not yet, anyway.)

The fight over gay marriage in our political realm is not actually about gay marriage, of course. Gays and lesbians will continue to hold ceremonies and cohabitate and call each other "husband" and "wife" no matter what the law says. The question is over a piece of paper, a government document that is usually a minor detail in the process of heterosexual marriages. For every gay or lesbian who angrily accuses the opposition of denying their right to get married, it is worth remembering that a marriage is not a document.

Perhaps the gay marriage issue needs to be discussed in new ways. Proponents could appeal to fiscal conservatives, "Let's subject gays and lesbians to the same IRS marriage penalty you've been enduring for years." Opponents could remind homosexuals of the full picture of modern marriage: "Do gays and lesbians really want to suffer the pain, grief and expense that comes from messy divorces? Doesn't the current law give you a handy excuse to dodge your mother's question of when you'll get married?"