The statistical trend is clear enough, but the question is more complex than may first appear. The Washington Post reported on June 6, 2010 that 25 percent of American households were mixed-faith in 2006, according to the General Social Survey. That represents a significant increase from the 15 percent of such households in 1988.
But, what does mixed-faith mean? It could mean the mixing of relatively similar Christian denominations, or it might mean the mixing of two very different systems of belief.
As Naomi Schaefer Riley reported, "In a paper published in 1993, Evelyn Lehrer, a professor of economics at the University of Illinois at Chicago, found that if members of two mainline Christian denominations marry, they have a one in five chance of being divorced in five years. A Catholic and a member of an evangelical denomination have a one in three chance. And a Jew and a Christian who marry have a greater than 40 percent chance of being divorced in five years."
That paper by Professor Lehrer is truly interesting. In "Religious Intermarriage In the United States: Determinants and Trends," published in the journal Social Science Research, Lehrer acknowledged that the span of differences "corresponds to a continuous variable." In other words, there is a huge difference between a marriage where a Presbyterian marries an Anglican and one in which a Baptist marries a Mormon.
Lehrer defined a couple as religiously intermarried if, for example, an Evangelical marries a Roman Catholic, or a spouse allied with a liberal Protestant denomination marries someone from "an exclusivist group." She then allowed, "Unions involving members of two ecumenical Protestant denominations are treated as homogamous."
All this points to a very interesting pattern. Part of the rise in the statistics about mixed-faith marriages is due to the increasing secularization of the liberal Protestant churches and denominations. To that must be added the huge increase in interfaith marriages among liberal Jews, and the more ecumenically-minded among other religious bodies.
Lehrer documented the fact that the more conservative faiths were not intermarrying at rates anywhere near the more liberal groups — and for understandable reasons. When the level of doctrinal commitment is low, the barriers to interfaith marriage are correspondingly far less significant.
Nevertheless, even with all this taken into account, it turns out that marrying outside the faith is one of the most significant risk factors for divorce. Citing the American Religious Identification Survey of 2001, Riley reported that "people who had been in mixed-religion marriages were three times more likely to be divorced or separated than those who were in same-religion marriages." Riley referred to this fact as "an open secret among academics."
Professor Lehrer described what she called the "large destabilizing effects" associated with mixed-faith marriages. Why is an interfaith marriage at such risk? The answer, in terms of the academic perspective of Professor Lehrer, is that "religion influences many activities that husband and wife perform jointly."
Or, as Naomi Schaefer Riley observed, "The differences between husband and wife start to add up." Seen in the context of the decisions that couples have to make in the course of life together, this is surely an understatement.
Putting all this together, it is clear that theological differences really do matter. These belief systems develop into worldviews that do have real consequences. It is not primarily a matter of which holidays the family observes, but how the children are raised, how the major decisions of life are framed, how the priorities of the couple are aligned.
The sociological data point in one clear direction — toward the inherent instability of true mixed-faith marriages. Even among the more liberally-minded, the tensions remain.
