SOME YEARS AGO OUR EXTENDED FAMILY GATHERED FOR THE HOLIDAYS. My young nephew Sam demanded that we do everything exactly as we had done it the year before, "because it's tradition." As a 5-year-old, Sam had no way to know that most of the details he remembered from the year before were things we did for the very first time that year -- hardly long-standing. But to Sam, they were the details he knew. They were natural and eternal -- "tradition." ¶ A similar lack of history surrounds current discussions of "traditional" marriage. Voters in California have amended their state constitution to define marriage as being a relation between one man and one woman. This bars same-sex couples from enjoying comparable social or legal support for their commitments. Why did supporters of Proposition 8 want to withhold from gay people the same social recognition that helps straight people make and keep vows of faithfulness? Why don't defenders of traditional marriage support fidelity and stability in same-sex relationships? It is not adequate to claim that marriage is an enduring fixture (the bedrock) of civilization. Marriage, in some form or other, may be a cultural constant. But forms of marriage vary dramatically through history, and those shifting forms always reflect the particular social values that regulate a society in a given time and place. Modern people would probably reject many earlier forms of marriage. The patriarchs of ancient Israel had complex households with multiple wives, and they begot children by their wives' servants as well as by their wives. Many early Christians shunned marriage altogether, some because they rejected the Roman form of marriage, some because they believed celibacy was better than any sexual marriage. Among social elites throughout history, most marriages were arrangements between families, designed to manage inheritance, control of land and political power. In the high middle ages, marriage was often loveless, while adulterous "romantic love" was celebrated in song and poetry. Many Victorian marriages were nearly sex-free because of the influence of an ideology of feminine purity. For centuries a husband had unrestricted legal access to his wife's body; there was no legal category of marital rape, and laws did not concern themselves with a husband's resort to physical violence in his own home. Each of these late -- not lamented -- forms of marriage made sense in its time because it matched the overall structure of society and reflected prevalent views of men, women and power.

Besides these, consider more closely two particularly dramatic transformations in the history of marriage: transformations involving coverture and interracial marriage. Coverture is the name for the old legal doctrine that meant a woman lost her independent identity and standing before the law at the moment of her marriage. Through long centuries in western societies, the wife became a legal nonentity -- part of the greater identity of the husband. She could not enter into contracts in her own behalf. She could not offer testimony in her own name. She could not defend herself.

One reason coverture seemed natural was that it mirrored the basic political structure of the time: a king ruling his subjects. As long as monarchy was the predominant political form, the husband's absolute rule in the household made sense, because the household was a kingdom in miniature.

The United States, of course, was founded in revolt against the absolute rule of monarchs. And the same upheaval in political theory that discredited the idea of monarchy led to changes in the template for marriage, which came to be seen as a covenant of equal subjects engaged in a mutual bond of love and commitment. The old form faded because it was not consistent with democratic values.

The end of coverture was opposed by traditionalists in apocalyptic terms. But no matter how tumultuous, the adjustment made marriage more consistent with the political philosophy of a democratic nation.

The challenge to recognize interracial marriages was another traumatic change in the form of marriage. For most of our nation's history, states could and did pass laws barring people of different races from marrying. In the context of widespread belief in white superiority, these laws felt right to the dominant majority that adopted them, while "race mixing" seemed like a violation of nature and divine command.

After the presidential election of 2008, those views seem to be almost incomprehensible antiquities. Nevertheless, as recently as the 1960s an interracial couple who married in Washington, D.C., were sentenced to jail by a judge who wrote that "Almighty God ... did not intend for the races to mix." Only in 1967 did the Supreme Court declare that laws barring interracial marriages were unconstitutional.

Like the movement to ensure women's equality in marriage, the movement to gain recognition of interracial marriages prompted dire warnings of the imminent collapse of civilization as we know it. Yet as our society rejects racist ideologies, we see race as irrelevant when two people are moved by love to commit themselves in marriage. We value love, commitment and stability more than we value racist ideology. So we reject impediments to interracial marriage in order to advance commitment and stability.

Defenders of "traditional" marriage have had electoral success. But the institution they defend is neither so natural nor so permanent as they imagine. The evolving form of marriage is always telling the story about what people in a given time and place value and what they don't. What basic social values are we defending by excluding gay people from the sustenance of marriage? As this discussion continues we will all need to decide whether our society values love, faithfulness and stability for everyone -- or just for straight people.

David Booth, Minneapolis, is an associate professor of religion at St. Olaf College in Northfield.