But when religious pluralism hits home — 22 percent of U.S. households now have more than one faith under one roof — the party's over for a growing number of families. Divorce is three times more prevalent in interfaith families with children than in same-faith households, according to the first national statistical look at the issue.

The American Religious Identification Survey 2001 finds that of all U.S. adults who have had children with someone of another faith, 10 percent are divorced, compared with 3 percent for parents of the same faith.

The finding emerged as demo-graphers looked in-depth at the survey's findings on the religious and spiritual choices of 50,000 people. Researchers from the Graduate Center at City University of New York were the first to ask people not only their own religious identity but also the faith of their current or former partner — and to ask how parents of differing religions were raising their children.

Few were surprised to add up 28.4 million Americans living in mixed-faith households, says Ariela Keysar, one of three co-authors of the survey. Couples come in more flavors than Life Savers: Baptist/ Methodist, Catholic/anyone, Jewish/Episcopalian, faith/no faith.

But the decisions they make for their children are not simply a private matter between each household and their higher power. The aggregate effects of parents' religious choices — from prenuptial negotiations through marriages and divorces — radiate across society as faith-based values guide belief and action in politics, education, health and ethics.

A 1990 study by Keysar, Barry Kosmin and Egon Mayer, the baseline for their 2001 survey, didn't ask these marriage, divorce and upbringing questions. "So it may be another 10 or 20 years before we can see which groups will gain or lose," Keysar says.

Those falling numbers alarm groups such as Southern Baptists who believe children must learn one absolute truth about God, and minorities such as Jews and Muslims who fear assimilation or seek the clout that comes with growing numbers to increase their influence in the public square.

Ibrahim Hooper, spokesman for the Council on American-Islamic Relations, says Muslim men, who are permitted in their religion to marry outside the faith, have trouble in custody disputes in U.S. courts. They are responsible for raising Muslim children, he says, but "we find the father's faith and ethnicity are used against him."

Often two distinct faiths can only work together if parents ignore theological gaps between divergent beliefs about the nature of God, the value and role of scripture and the path to salvation.

If Methodist Mom says all good people go to heaven, but Baptist Dad says salvation is only through Christ, it can be a ticket to confusion or indifference for kids, says religion researcher George Barna.

He says children need one faith because, "without it, you wind up without an anchor, a community and a worldview for making decisions internally and eternally."

But millions of Americans say mixing it all up works just fine.

No lasting psychic fallout

So far, mental-health experts have seen no lasting psychic misery inflicted by growing up with parents who take opposite stands, says Los Angeles attorney Marshall Zolla, a family law specialist.

Ed Johnsrud, whose grandparents came from a tiny Scandinavian fundamentalist Christian sect, married Patti Oblath, a Jew, and promised to his raise children as Jews.

When the Los Angeles couple divorced, he kept the agreement for their daughter but insisted on custody at Christmas, even though for him it's a cultural event, not a religious one.

"I'm not celebrating the miracle of Christ's birth. I'm celebrating the American tradition of celebrating Christmas," Johnsrud says.

Broadcast news commentators Steve and Cokie Roberts often talk about their success honoring his Jewish and her Catholic traditions. They are favorite speakers for the Dovetail Institute, which publishes newsletters and handbooks for parents on multifaith ceremonies and holidays.

But Martin Marty, Lutheran pastor and church historian, says the trend to "celebrating celebration" trivializes religious teachings, undercutting their power to inspire, guide and comfort lives.

A rival group to Dovetail, InterfaithFamily.com, calls on parents to pick one religious identity for kids.

Andrea King of Santa Monica, Calif., who contributed several essays to the group's handbook, The Guide to Jewish Interfaith Family Life, quotes a 17-year-old girl: "Having a religion should be like having a hometown" where "you know everyone and all the rules. You don't have to stay there, but you always know where it is, and you can come back whenever you want."

King observes: "When people mush it all together so the kids get all parties and no content, these (teens) will defend their parents at first. They will say their parents did the best they could. But, eventually, as you listen closely, a significant number will say, 'I wish my parents had made a choice. I don't feel comfortable anywhere.' "

Battles over "soul" custody are turning up in divorce court with increasing frequency as former couples struggle over the spiritual upbringing of their offspring. When couples part, their sometimes-tenuous agreements on what they value for their children often come unglued, says Harvard Law professor Martha Minow.

And attorneys and mediators increasingly see Christian vs. Christian and Jew vs. Jew when one parent turns devout in belief and practice while the other doesn't. Santa Monica Rabbi Jeffrey Marx, a professional divorce mediator, recently divvied up Muslim feast days between two Muslim parents.

Marx says religion is an issue in 95 percent of interfaith marriages and divorces, but only 20 percent of the time is it a thorny theological point.

More often, he says, former partners club each other with the visitation schedule or try to appease in-laws. He negotiated one prenuptial agreement setting the exact height for the Christmas tree.