Interfaith marriages have helped spread religious tolerance in society but can present intractable problems for some couples.
Interfaith marriage has never been so visible or so popular in America as it is today. Steve and Cokie Roberts, Larry and Shawn King, Chelsea Clinton and Marc Mezvinsky: Interfaith couples occupy a prominent place on the public stage, not to mention a prominent role in the private lives of Americans. Almost one in two marriages in the U.S. are between people from different faiths, a historic high.
The rise of interfaith marriage can be read as but the latest success story in the continuing American Experiment, wherein differences of all sorts are fused into a single, vibrant polity. As Naomi Schaefer Riley notes in " 'Til Faith Do Us," most Americans see interfaith marriage "as a confirmation of American tolerance, of our progress as a society." To judge by Ms. Riley's engaging and incisive account—combining clear-eyed analysis with polling data and the details of more than a hundred interviews—interfaith marriage has indeed brought about a wider acceptance of America's many religions and religious backgrounds even if, as she shows, it has created a few problems of its own.
Millions of Americans, it is clear, have learned from their own spouses—or from the marriages of friends and family members—about faiths other than the ones they were born into. In doing so, they have come to value or at least understand otherwise alien rituals and doctrines. If differences between religious traditions are no longer a source of serious social division in the United States these days, Ms. Riley argues, one reason appears to be that couples bridge the divide themselves.
As one might expect, there are many reasons for the rise of interfaith marriage. They range from the ever-greater frequency of children going off to college—an experience that brings Americans from diverse backgrounds together—to the growing power of American individualism, which puts a premium on choice over collective identity. In recent years, Ms. Riley notes, what might be called the "soul mate" model of marriage has grown more popular as well, increasing the possibility of people from different faiths choosing to make a life together. According to this model, marriage is primarily an expressive connection rather than an institution that bundles romantic love, children, religious faith and mutual aid (material and social).
Thus many Americans begin their marriages believing that love will conquer all, including religious differences. But when the honeymoon is over, love proves less than omnipotent, and religious differences may reassert themselves, especially after children arrive. "Deciding how to raise children," Ms. Riley writes, "is probably the highest hurdle interfaith parents face."
Are the kids to be raised Muslim or Mormon? Is a Christmas tree appropriate in a half-Jewish home? Should Johnny be sent to both the (evangelical) Young Life group and (Catholic) religious education? One Jewish-Catholic couple interviewed by Ms. Riley (a former member of The Wall Street Journal's editorial-page staff) found themselves arguing over whether to baptize their daughter. Questions like these can "tear at the fabric of a marriage," Ms. Riley says; this particular couple ended up in divorce court because of their religious disagreement about child-rearing. Ms. Riley notes that couples from different faiths would do well, in the courtship phase of their relations, to discuss child-rearing's religious dimensions.
And perhaps life's other religious dimensions. On average, Ms. Riley says, interfaith couples are less likely to be happy in their marriages and—in some combinations—more likely to divorce than couples who share the same faith. There may be a religious cost as well—for the married couple, a loss of steadiness in observance and belief. Meanwhile, the children raised in interfaith homes are more likely than the children of same-faith homes to reject their parents' faiths. " 'Til Faith Do Us Part" finds that the children of interfaith couples, in their early years, are less likely to attend religious services and less likely, as adults, to affiliate themselves with a religious tradition. A record-setting 32% of young adults say that they have no religious affiliation, according to the Pew Forum on Religion and Public Life. The rise of interfaith marriage may well be a cause.
It turns out, then, that interfaith marriage shores up the American Experiment in certain ways, fostering tolerance and reciprocal regard, and yet undermines it in others, weakening the family and the religious ties that have long bound Americans to one another. Religious groups in particular have reason to be concerned, as the chain of belief and affiliation, from one generation to the next, is broken. But what can they do in a society as pluralistic and tolerant as America has become?
Ms. Riley concludes her reporting and analysis by suggesting that religious communities strike a delicate balance in their approach to interfaith marriages and families. On the one hand, they must welcome them if they wish to keep up a connection with the believing spouse and his or her children. But they must also provide a strong sense of community and a gracious but confident expression of their own religious worldview. "Regularly engaging nonmember spouses in conversations about the faith is important," she writes, noting that such engagement, if done with a soft touch, may bring the spouse into the fold. Finally, religious communities must focus more on reaching young adults, giving them a venue where they can engage their religious faith in a new way and meet a "soul mate" who draws them closer to the fold rather than leading them away from it.
—Mr. Wilcox is the director of the National Marriage Project at the University of Virginia.
A version of this article appeared March 23, 2013, on page C6 in the U.S. edition of The Wall Street Journal, with the headline: When Two Traditions Wed.