A few weeks ago, I found myself speaking about interfaith marriage at a Reform synagogue in a wealthy suburb of New York. I’ve given many of these talks since the publication of my book on the topic, ’Til Faith Do Us Part: How Interfaith Marriage Is Transforming America. During the Q & A session, a woman whose daughter had recently married a non-Jew started a familiar speech. She kept saying to me and the other audience members, “There’s nothing you can do. Your kids will go out and meet all sorts of people. They love the diversity.”

“Love the diversity.” It’s an odd turn of phrase, and not entirely accurate. It’s true that many champion “diversity” as a moral ideal and social good. But it’s never entirely clear what counts as diversity. Official statements notwithstanding, for all practical purposes Asians in higher education today no longer count as “adding to diversity.” Moreover, “love” isn’t quite right either. By my reckoning, Americans are motivated more by the fear of seeming narrow or intolerant than by a desire for something as vague as “diversity.”

That said, the woman at the synagogue was drawing attention to a real change in our society. In just two or three generations, there has been a radical reversal of racial attitudes, something we see with especial clarity in one of the most intimate modes of social commerce—marriage. According to a recent Pew survey, about nine in ten adults between the ages of eighteen and twenty-nine say they would be fine with a family member marrying someone of another race. About one in seven new marriages in America is now interracial, and the numbers are higher for younger Americans.

And it’s not just race. An affirmative ethic that transcends traditional ways of categorizing people extends to sexual orientation, culture, and socioeconomic background. These days, it’s bad style to be seen as non-inclusive. (The one exception is political affiliation. Inter–­political party marriage rates have barely budged in the past half century. Ideology still divides, not least the ideology of diversity.)

This holds true for religion as well. The American interfaith marriage rate is at 36 percent (if you throw all Protestants into one group). This has a lot to do with the diversity ethic. As a Catholic woman told me about her thinking when she went off to college, “To limit yourself to only people of your own religion seemed bigoted. . . . There is a whole world of people that I don’t know.” To write them off as potential partners before she’d even met them “seemed rude.”

The language is revealing. It’s as if our society’s institutional rules about hiring an employee or admitting someone to college have morphed into rules for dating. To say that you were “discriminating” in choosing a spouse used to be a good thing, but that word’s positive connotation has probably been lost to the dustbin of history.

A fear of discrimination, with its racial overtones, has now come to influence many of our decisions, even ones that require, well, discrimination in the older sense of considered judgment. It seems to go against our national grain now even to ask people their religious beliefs on a date. A nationally representative survey I commissioned in 2010 revealed that more than half of interfaith couples didn’t discuss what religion they wanted to raise their children in before they got married.

I think a social ethic of tolerance and inclusion is entirely appropriate. But I find it very odd—indeed, unwise—to extend it to interfaith marriage. It’s a view that I’ve found consistently controversial, even when speaking to religious audiences. When I lecture about interfaith marriage, I am regularly asked why interfaith marriage should be thought of any differently from interracial marriage. Isn’t selecting a spouse on the basis of religion as invidious as doing so on the basis of race?

It is true that in the past interracial and interreligious marriages were often treated in similar ways by society. In a 1964 book, Intermarriage: Interfaith, Interracial, Interethnic, sociologist Albert I. Gordon described the difficult circumstances that faced couples in all three groups in the first half of the twentieth century. They were often shunned by their families and communities. Many could not even find a place to live where their children would not be subject to harassment.

Today, we indiscriminately censure the social attitudes that made life so difficult for those who marry across racial, ethnic, and religious boundaries. It is not uncommon for middle- and upper-class Americans to seek out diverse neighborhoods and to worry aloud that their children are not encountering enough people from other races. Religious mixing has also been welcomed, albeit to a lesser extent. When people find out that my children are products of a Conservative Jew married to a former Jehovah’s Witness (now nonbeliever), they give me a kind of “only in America” smile. (Diversity is probably one of the few remaining reasons that liberals may tout American exceptionalism.)

There are some enduring similarities. Both interracial and interfaith couples are at a higher risk for divorce, according to some studies. Marriage counselors and researchers have long known that the more a couple has in common, the more harmonious their marriage is likely to be. Which is certainly a good argument for discussing differences (of any sort) ahead of time, no matter how strongly you believe in the importance of an inclusive society.

But more important, as someone married to a man of both a different race and a different religion, I’ve come to believe we should think very differently about interfaith and interracial marriage. Living in a particular faith means adhering to a certain set of principles that shape married life and the way we raise our children. Having a certain skin color does not.

We are born with our racial differences and, although in many ­societies those differences become lines separating very different cultures, in themselves differences of skin color are largely superficial. Religious identity, on the other hand, isn’t a biological given. Even if religion can be seen as an accident of birth—an idea that can frequently be heard even in certain fairly religious quarters these days—it is not simply a superficial characteristic the way race or ­ethnicity is. True, my parents are Jewish, but my Judaism isn’t automatic. It’s something I’ve internalized in a deliberate way. Religion engages our freedom, and for this reason we rightly feel the differences in religious identity as truly substantive. They ­influence us in deep ways.

In my work, I’ve found that many interracial and interfaith couples disagree with me. Indeed, it now seems more important for many (­non-white) people to pass down a sense of racial identity to their children. Religion, though, is something that right-thinking people assume they can fudge.

Indeed, most Americans believe that religious differences can be bridged if a couple holds other guiding principles in common. In my survey, I asked respondents to choose between the following claims:

It is better for everyone involved if a husband and wife have the same religion.

What really matters is that a husband and wife have the same values, regardless of their religion.

An overwhelming majority (79 percent) of married Americans chose the second. Americans see the advantage of having two spouses of the same faith. But they are not willing to put religion ahead of “common values,” a more inclusive-sounding phrase.

“Common values,” I found in my interviews, is a phrase that stands in for one of two things: treating other people with respect or giving back to the community. There is nothing wrong with such values, obviously. In fact, one would be hard-pressed to find anyone walking down the street who does not subscribe to them.

Our educational and political leaders keep suggesting that bringing people together from diverse backgrounds—whether it is racial, ethnic, gender, sexual orientation, or some combination of the above—makes for better schools, more effective workplaces, and even morally superior environments. Religion has gotten lumped in with all these other immutable personal traits—what I think of as the racialization of religion. And we’re doing this despite the fact that Americans’ faith views seem to be so much in flux and religion-switching is at an all-time high. This celebration of diversity now erodes our ability to think clearly about religion and marriage. But religion is not race, and a marriage is not a public school.

Religion embeds values within us—sets of principles that are not to be taken lightly or easily discarded. If people are to be soul mates—if, as many say, the important thing is to find a partner who shares one’s values—then religion is something that must be taken into account. Religion makes values specific. It offers a set of texts, a code of behavior, and even a group of leaders that can make those values into something more substantive and more of a basis for action than the call to “be a nice person.”

Confused and misused, “diversity” may nevertheless be a good cultural message for many aspects of life. But the goals of a marriage are not the same as those of schools, civic organizations, or elections. Obviously husbands and wives will differ on what they hope to get out of marriage, but surely it’s some combination of achieving personal happiness and building a family, and religion is a factor in both of those. There is nothing about having diverse perspectives in a marriage that will make it inherently better—in fact, it may be less likely to succeed in the long run.

Naomi Schaefer Riley is a weekly columnist for the New York Post.