Drive down 16th Street in Washington, and you will see evidence of the religious diversity that has struck visitors to America since Toqueville. Church after church will flash by: Grace Lutheran, the National Church of the Nazarene, Trinity A.M.E. Zion, All Souls Unitarian. And on and on. To a small group of sociologists, the reason there are so many kinds of houses of worship is no different from the reason there are so many brands of detergent or toothpaste at the supermarket: economics.
Competition, and supply and demand, shape the earthly aspects of religion - its popularity and how it is delivered - they say. And people in pews are fickle consumers, ready to bolt to a competing brand if the current one seems stale or uninspired.
This economic approach has led them to conclude that competition, rather than undermining belief, actually spurs it. Not only does it make clergymen work harder, they say, but it also means there is a greater likelihood that any one person will find a church that suits his spiritual tendencies, whether New Age or biblical literalist.
"It can be demonstrated that in any society there is a distribution of religious tastes and concerns," said Rodney Stark, a professor of sociology at the University of Washington and a leading proponent of what is known as the religious economies theory. "The basic point is that any society would be better served by many different religions focusing on - if you want to use market language - different market segments. I'm sure we drink more soda pop because there are 20 companies out there, rather than just Coke." Why wouldn't religion be the same, he asks?
Religious pluralism, Mr. Stark and others say, explains why the United States is so religiously vibrant, while much of Western Europe has seen a decline in interest in traditional churches.
But both the economic language and the pluralism argument have upset many in the field. Steve Bruce, a sociologist at the University of Aberdeen in Scotland, has written that the sociology of religion is suffering from "the malign influence of a small clique of U.S. sociologists" who are peddling daft ideas. And Mark Chaves, a sociologist at the University of Arizona, calls the pluralism theory a "house of cards," collapsing under close scrutiny.
The religious economies scholars, who focus on the variety of Christian denominations, are trying to tear down the view of pluralism that has reigned in the sociology of religion for a half-century. It was perhaps most famously articulated by Peter Berger in his 1969 book, "The Sacred Canopy." Mr. Berger, now director of the Institute on Religion and World Affairs at Boston University, wrote that faith was once like an awning that sheltered all of society, offering citizens a common certainty. But as tolerance opened the door to different varieties, the canopy tore: certainty could not help but decline, and faith followed. Mr. Berger made his case through broad historical and cultural analysis.
But Mr. Stark and Roger Finke, a sociologist at Penn State and co-author of "Acts of Faith: Explaining the Human Side of Religion" (University of California, 2000), argue that this big-picture sociological view is often woolly and unscientific. They say, too, that a new theory is needed to make sense of America. In the United States today, some 40 percent of adults claim to attend church weekly, compared with 10 percent in Britain and 4 percent in Scandinavia. With some 1,350 denominations and sects, according to the Encyclopedia of American Religions, the United States is at once one of the most pluralistic and one of the most religious modern societies. Those facts have forced sociologists to rethink the idea that religion would die out when neighbors stopped believing in the same God.
Adam Smith drew some links between competition and religious commitment in "The Wealth of Nations" 225 years ago, but most scholars ignored them. Mr. Stark and others started using economic language to describe religion in the mid-1980's.
The new brand of thinking started making waves, however, in 1988, when he and Mr. Finke published an article in the American Sociological Review. Using data from an unusually thorough survey of religious behavior in 1906, conducted by the United States Census Bureau, they explored the link between religious diversity and commitment. (Such information is no longer gathered by the government.)
The secularization thesis held that religion would decline most rapidly in cities, because it would be impossible for urbanites not to notice that their neighbors headed off to different churches. But Mr. Stark and Mr. Finke found that rural areas had attendance rates of 50 percent, while some urban areas had rates as high as 60 percent.
Their methods were as startling as their arguments. They used the same statistical formula that the Federal Trade Commission uses to measure the amount of competition in consumer markets (like software) to look at pluralism even more closely. They found that in towns of similar size, church attendance was highest when there was a choice of worship.
"Contrary to the pleas of the clergy and the pronouncements of social scientists," they concluded, "pluralism is friend, not foe, to religious mobilization."
In 1991 Larry Iannaccone, an economics professor at Santa Clara University, went international with the theory. In an article in Rationality and Society, he argued that 90 percent of the variation in religious commitment among European states, the United States, New Zealand and Australia was attributable to differences in pluralism. Since then, there has been a flood of articles, often by these same three scholars, applying the thesis to various countries and periods.
The real difference between religion in America and Europe, they propose, is on the supply side. Mr. Stark's European colleagues are baffled, he says, when he describes the raft of church solicitations he gets in the mail. They have never heard of such a thing. "I tell them: `That's the point. You don't understand.' American churches work very hard at reaching out to people to bring them in."
One of the most controversial of Mr. Stark and Mr. Finke's arguments is that Europe could wake up religiously if its churches started acting like their American counterparts. That strikes some scholars as absurd. Even those who think the theory works for America say it fails in Europe. For one thing, in Poland and Ireland (and also in Quebec) the Catholic church has few competitors, and yet faith and attendance at Mass are very high.
Additionally, several sociologists who specialize in Europe's Protestant countries have said open competition and the decline of traditional religion have gone hand in hand. Mr. Bruce of the University of Aberdeen has said that was the case for Britain. "Dull as it may be to say so," he wrote in 1999, "the old orthodoxy was by and large right."
Other scholars question whether the pluralism theory is even applicable to the United States. A widely discussed paper in the American Sociological Review two years ago, by Daniel V. A. Olson of Indiana University at South Bend, attacked the statistical methods used by Mr. Finke and Mr. Stark.
And an article in a forthcoming issue of the Annual Review of Sociology by Mr. Chaves and Philip S. Gorski of the University of Wisconsin at Madison, concludes that of 26 articles published in respected scholarly journals on religious pluralism in various countries, 16 found either no pattern in the relation between pluralism and religious commitment or found that pluralism hurt religious commitment.
The pluralism argument is crucial for the religious economies scholars, Mr. Chaves said, because "it is the one place where they have a claim to an empirical `discovery.' " But he added, "It is clear to me the weight of evidence is massively against this."
In some of the studies of America, Mr. Finke and Mr. Stark treated Catholics differently from followers of other faiths. Critics have called this statistical sleight of hand. But the pair said that as a tightly knit, often persecuted minority - at least in the 19th century - Catholics did not take part in the same economic market as Protestants. Mr. Finke and Mr. Stark often focus on 19th- century America because the important issue, they argue, is whether having one, two or three churches makes a difference.
As far as Ireland and Poland are concerned, Mr. Stark and Mr. Finke counter that even monopoly churches can thrive when religion and political conflict get entwined. The Poles, for instance, long saw attending Mass as a way of thumbing their noses at the Soviets. To critics, however, that line of argument sounds self-justifying.
Still, even the critics concede that America's staggering level of faith demands more study and more theorizing. Mr. Berger, author of "The Sacred Canopy," has modified his views on whether and how America is secularizing. In an interview he said he no longer thought pluralism dissolved faith entirely, although he maintained that it changed the character of belief, making it more tentative and malleable, even in America.
He declined, however, to give the religious economies thinkers credit for his own shift. Like many others, he thinks a market-based view of religion misses most of what's important - for example, he said, history, meaning, symbolism and ritual. "To look at religion from a framework derived exclusively from economics," Mr. Berger said, "is not very helpful."