If the court officially severs the ancient connection between marriage and procreation, then it really has no grounds for denying marriage to these other ensembles. If there is a limit to the principle, then Kennedy et al. are obligated to declare what it is in advance. So far, Kennedy hasn’t done that. And it is not too much to ask him to do so before declaring out of whole cloth a constitutional right to same-sex marriage.

Nearly every experienced observer expects the Supreme Court to make gay marriage a constitutional right this June. Justice Kennedy will be the key figure in this decision, as he has been in all the precedents leading up to this point. And Kennedy has made it clear that the only possible reason for opposing legal gay marriage is irrational animus against gay people. Neither he nor the other justices have adequately considered that there might be a rational basis for defining marriage in connection with procreation.

In a very helpful article at First Things today, Hadley Arkes observes that Kennedy has not considered other arguments because the Court’s conservative justices have not made them. Instead, the conservative justices have been making a narrow case based on federalism that the matter should be left to the states. But that has proven to be a dead-end and will not stop the seemingly inevitable decision to come this summer. Because of this, Arkes says that the conservative justices need to try a new tack. They need to make Kennedy explain whether there will be any limit to the principle that the Court is about to establish. If the Court rules that the law cannot privilege procreative unions over non-procreative ones, where does that end?

Arkes has basically thrown down the gauntlet to the conservative justices. Arkes says that conservative justices cannot retreat into federalism and allow Kennedy to evade the implications of his decision. Arkes writes:

The question may be put to the judges with a sharpness that hasn’t been directed to the judges themselves quite in this way in the past. And so, if Justice Kennedy, writing for the Court, sweeps away the last barriers to same–sex marriage, what will be contained in the “principle” he articulates as the ground of the decision that would indeed bar marriage to:

—the widows or widowers who would simply wish to pool their social security and savings;

—the “throuples” who wish to marry the ones they love in this three-some;

—the polygamous couples living with the consent of the participating adults in these intimate relations, still barred in the laws;

—the adult fathers and daughters, mothers and sons, invoking the words of the Supreme Court of Massachusetts and avowing their earnest interest in living with the ones they love in caring relations of “adult intimacy”;

—and finally, the adult fathers and sons, mothers and daughters.

If the court officially severs the ancient connection between marriage and procreation, then it really has no grounds for denying marriage to these other ensembles. If there is a limit to the principle, then Kennedy et al. are obligated to declare what it is in advance. So far, Kennedy hasn’t done that. And it is not too much to ask him to do so before declaring out of whole cloth a constitutional right to same-sex marriage.

Arkes’s article is thoughtful and long and well-worth the read. You can find it here.

Denny Burk is Associate Professor of New Testament and Dean of Boyce College, the undergraduate arm of the Southern Baptist Theological Seminary. This article first appeared on his blog and is used with permission.