IS MARRIAGE WORTH a constitutional amendment? A fair number of conservatives think not. "Leave it up to the states!" urges John McLaughlin. George Will, with customary eloquence, calls "constitutionalizing social policy" both a "misuse of fundamental law" and "imprudent . . . at a moment when we require evidence of the sort that can be generated by allowing the states to be laboratories of social policy." William Safire sees civil union as one of the "basic rights" that should be recognized in every state, "popular statutes to the contrary notwithstanding," though he cannot quite come to grips with what to do about same-sex marriage except to say that activist judges should probably leave the issue alone.

But activist judges won't leave it alone. With the recent Goodridge decision in Massachusetts, they are already opening the door to gay marriage. Why, then, do so many conservative voices reject the only possible effective political response?

One reason may be that many on the right view marriage as fundamentally a "values" issue. Marriage gets classified as "culture," which means private, not public; at best as "social policy," in George Will's term. If marriage is conceptualized in this way, many conservative intellectuals are led by their commitment to federalism to reject the idea of defining marriage in the U.S. Constitution. Let states experiment with different social policies and find out what works best. This view of marriage as a values question is shared by many on the left. And it seems to be the view of the Goodridge court, which pays tribute to marriage as a social institution with this rather limited list of reasons why marriage matters to anyone beyond the individuals it joins:

Civil marriage anchors an ordered society by encouraging stable relationships over transient ones. It is central to the way the Commonwealth identifies individuals, provides for the orderly distribution of property, ensures that children and adults are cared for and supported whenever possible from private, rather than public funds, and tracks important epidemiological and demographic data.

By contrast, when the court touches on the individuals' interest in marriage, it waxes positively poetic: Marriage "fulfills yearnings for security, safe haven and connection that express our common humanity" and is "among life's momentous acts of self-definition."

So from right to left, many express disapproval of changing our sacred Constitution on behalf of marriage. They're happy to concede that economic matters belong in the Constitution. The right to bear arms? Sacred (at least on the right). Excise taxes and the inviolability of contract? Naturally. Yet many seem to believe that a Constitution filled with such things will be somehow tainted by the mention of a girlish issue like making sure that "marriage in the United States shall consist of the union of a man and a woman."

Until quite recently, most educated Americans had a different view. When the United States refused to admit Utah to the Union unless it rejected polygamy in the late 19th century, lawmakers and judges agreed: Marriage was not just a private taste or a values issue or even a religious issue, it was one of the handful of core social institutions that make limited government, and a constitutional republic, possible. Shared family norms enshrined in law were at least as vital to the republic as norms about property rights and democratic government.