WASHINGTON — At the Normandy American Cemetery on the cliff above Omaha Beach, there are rows and rows of crosses and Stars of David. Certainly, many buried there were not religious. But the overwhelming majority of Americans in the mid-20th century identified themselves culturally as Protestants, Catholics or Jews, no matter their personal beliefs.

This cultural expectation has begun fading in American life. The fastest-growing religious affiliation today is the lack of religious affiliation — the rise of the "nones," as in "none of the above," who now constitute nearly 20 percent of the population.

For some, this is an indication that America is finally on the path of secularization taken by much of Europe, where non-religious funerals have become common and half of Europeans have never attended a religious service. Much of modern sociology has been premised on the notion that modernization and secularization go together.

In America's case, the hypothesis remains unproved. While Americans have become less attached to religious institutions, there is little evidence they have become less religious. In 1992, according to the indispensable Pew Research Center, 58 percent of Americans described religion as "very important." In 2012, it was ... 58 percent. There is a similar stability in the proportion of Americans who regard prayer as an important part of their lives.

It is Europe that remains the global religious outlier. America has about the same level of religious commitment as does Latin America. As Robert Putnam of Harvard University points out, "The average American is slightly more religious than the average Iranian."

America is not a secularized country. But the relative decline of institutional religion has public consequences. While the number of the devout has remained steady, fewer of those in the religious middle identify with the organizations and values of the devout. What we are seeing, according to Luis Lugo of Pew, is not "secularization but polarization." Institutional religion has gained a larger body of critics.

On the level of politics, this trend aids cultural liberalism and the Democratic Party. About 70 percent of the nones voted for President Obama. They are more liberal than the religiously affiliated on issues such as abortion and same-sex marriage. In fact, nones are now the largest religious category in the Democratic coalition, comprising 24 percent of Democratic and Democratic-leaning voters.

This sets up some possible conflicts within the Democratic Party. Its second-largest religious group is black Protestants, among the most religious of Americans. How included will they — or liberal Catholics or progressive evangelicals — feel as Democratic ideology becomes more secular and secularizing?

But the main tension is emerging between the parties. Religious conservatives remain the largest constituency within the Republican Party. So America is moving in the direction of having one secular party and one religious party, bringing polarization to a new level of intensity. This is movement in the direction of Europe, which has been cursed by the conflict between anti-clerical parties and religious parties. For America, this could be a dangerous source of social division, with each side viewing the other as theocrats or pagans. There is no contempt like the contempt of the true believer or the militant skeptic.

Those cheering the trend of religious disaffiliation should consider some broader social consequences. The rise of the nones is symptomatic of the decline of many forms of belonging. According to Pew, all of the recent growth in the nones has come among those who are not married. This indicates a group of people distrustful of institutions, with marriage being the most basic of institutions. The unaffiliated donate less to charity than the affiliated. They participate in fewer volunteer organizations. Individualism can easily become atomization. Whatever else you may think of the communitarian creeds, they help create community.

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Can these creeds adapt to changed cultural circumstances and renew their appeal? Sociologists such as Roger Finke and Rodney Stark provide evidence that it has happened before. At the time of the American Revolution, institutional religion was ossified and only about one-fifth of Americans were church members. Around the Civil War, it was perhaps a third. Today is it is more than half. Over a period of rapid social and economic change, Methodists, Baptists, then Pentecostals found ways to attract new members. "The churching of America," Finke and Starke conclude, "was accomplished by aggressive churches committed to vivid otherworldliness."

In religion, it is easy to measure what is dying; it is harder to locate the manger where something new is being born.

Michael Gerson's email address is michaelgerson@washpost.com.