In 1790, before there was a First Amendment, George Washington sent a celebrated message to the Jews of Newport, Rhode Island: “It is now no more that toleration is spoken of as if it were the indulgence of one class of people that another enjoyed the exercise of their inherent natural rights, for, happily, the government of the United States, which gives to bigotry no sanction, to persecution no assistance, requires only that they who live under its protection should demean themselves as good citizens in giving it on all occasions their effectual support.” As if to emphasize that these views were more than cold Enlightenment abstractions, he added near the end of his May the children of the stock of Abraham who dwell in this land continue to merit and enjoy the good will of the other ­inhabitants—­while every one shall sit in safety under his own vine and fig tree and there shall be none to make him afraid.”

Though frequently stretched and pummeled in the two centuries since they were enunciated, Washington’s principles have generally defined enlightened American opinion on the relation of religious bodies to the state, as well as to one another. Americans have fought over a great many issues, but religion has seldom been a source of violence since the colonial era. Even in times and places where ­anti-­Catholicism and ­anti-­Semitism were common, the volume of actual blood and tears shed over differences of faith has been piddling compared with the effusions in Europe in the 17th century or the Middle East today. Perhaps the greatest struggle between tolerance and conformity to the majority’s mores occurred in the late 19th century when the federal government forced the Mormons to abandon ­polygamy.

While religiously motivated bloodshed remains mercifully rare in the United States, the ideals proclaimed by Washington seem to be under severe pressure, if not actually breaking down. They also look more naive than they did 40 or 50 years ago. What Washington and ­many later Americans chose to ignore, for perfectly understandable civic reasons, is the tendency of ­full-­strength religion, with its sublime and dangerous certainty in matters of principle, to cause discord in a pluralistic society. Today, renewed struggles over the place of religion in institutions at every level, the celebration of Christmas in public venues, God in the Pledge of Allegiance, the legality and propriety of ­same-­sex marriage, courthouse displays of the Ten Commandments, and the status of biological evolution in education spill rivers of ink and spawn endless litigation. The Left fears that fundamentalists have subverted the Constitution to establish a theocracy, while the Right complains of galloping secularism. Every U.S. Supreme Court confirmation becomes a battle over the ­quasi-­religious issue of abortion. War between the faiths, as well as between faith and government, is raging again throughout most of the world, and America is part of the ­picture.

It seems scarcely believable that when Jimmy Carter ran for president in 1976, many people outside the South had never heard the phrase ­“born-­again Christian.” In the 1980s and ’90s, eminent sociologists of religion including Alan Wolfe and Robert Bellah, following the lead of Alexis de Tocqueville a century and a half earlier, still thought that a long tradition of “religious individualism,” together with the high value Americans place on being nonjudgmental, could be counted on to preserve civic harmony. Today that judgment seems far too ­optimistic.

The abstract term “religion,” as employed by Washington two centuries ago and accepted more or less without examination by most Westerners today, implies a basic similarity among the phenomena it names. From the relatively uncontroversial insistence that all religions are equal before the state to the stronger claim that all possess equal intrinsic validity seems a short and natural step, one that received further encouragement from the rise of comparative religious studies in the 19th century. This claim of substantive equality may imply that most or all faiths have an essential core of beliefs in common, such as the power and goodness of God, and that the religious conflicts of the past involved doctrines or practices of little importance. On the other hand, the assumption that all religions are equally true may simply be a tactful way of saying that all are equally false. In either case, the idea gained popularity because it seemed to carry the democratic virtue of tolerance a long step further while sidestepping theological questions. “If the primary contribution of religion to society is through the character and conduct of citizens,” wrote Bellah approvingly in Habits of the Heart (1985), “any religion, large or small, familiar or strange, can be of equal value to any other.”

Several factors, however, complicate this generous presumption of equality. One is that not everybody shares the same notions of good character and conduct. Another is that actual ­religions—­Christianity in its many forms, Judaism, Islam, to name no ­more—­embody conflicting claims about the universe and human life whose truth or falsity is not easy to ignore. Serious religion is more than a diffuse collection of attitudes and sentiments. Adherents who stand by the historical claims of their own faith cannot without contradiction either accept the essential equality of other religions or play by the rules of tolerance that date from the Age of Reason. By the same token, believers find it hard to go along with secular or scientific claims that contradict what they regard as revelation. This familiar state of mind has often been described as a revolt against modernity, whether it occurs in Alabama or Saudi Arabia; but if modernity is equated with secularism, the statement is little more than a ­tautology.

Thomas Jefferson’s epigram, “But it does me no injury for my neighbor to say there are twenty gods, or no god. It neither picks my pocket nor breaks my leg,” is often quoted as a model statement of democratic tolerance. Yet it depends entirely on the questionable assumption that my neighbor’s gods are harmless introverts. Suppose instead that they aggressively command him to confine women in the home, to marry several of them at once, to forbid me from pursuing business and pleasure on the Sabbath, or to convert (if necessary by force) everyone whose convictions differ. What then? These possibilities are hardly fantasies. If you really believe as a matter of divine revelation that salvation comes only through the person of Christ or the teachings of Muhammad, you may reluctantly accept the civic equality of competing faiths, or of unbelief in any faith, as a practical necessity. But deep down you can hardly avoid regarding them as damnable errors rather than the exercise of a natural ­right.

In the American context, saying so would violate a host of ­long-­established customs, with the result that those who express negative opinions toward other religions are widely repudiated as extremists even by their fellow believers. Throughout the Muslim world many people are more outspoken, to say the least. So are many Christians in Africa, a numerous and growing body of the faithful who shook the worldwide Anglican Communion to its already cracking foundations by demanding that the American Episcopal Church either repent for having consecrated an openly homosexual bishop in 2003 or be expelled from the Communion. (Of course, in the view of traditional Christians, it was the Americans who did the shaking.)

What is known in the United States as “mainline” Protestantism on the whole evades divisive questions about the truth or falsity of traditional doctrines. The decline of the mainline churches in numbers and prestige is a major factor in the controversies that beset church and state in America today. “Throughout the 19th century and well into the 20th,” writes Bellah, “the mainline churches were close to the center of American culture. The religious intellectuals who spoke for these churches often articulated issues in ways widely influential in the society as a whole. But for a generation or more, the religious intellectuals deriving from the mainline Protestant churches have become more isolated from the general culture.”

Although the more confrontational branches of Christianity that still believe in sin and hell are often dismissed by the media as a cranky fringe, they have far more members than the formerly dominant mainline churches. There are more than 67 million Roman Catholics in the United States, overwhelmingly the largest membership of any religious body. (Catholics are now informally accepted as mainstream by the press and other cultural institutions, provided they reject the teachings of their church on birth control, abortion, homosexuality, papal infallibility, and women in the priesthood, as many American Catholics do.) Among Protestants, the Southern Baptist Convention, regarded by many critics as a network of provincial fundamentalists, dwarfs all other denominations, with more than 16 million members. There are more than five million Mormons; and the Mormon church, like the Southern Baptist Convention, is still growing. Mainline sects, on the other hand, have been losing members for decades. The largest Methodist denomination has just above eight million adherents. The once-powerful Episcopal Church now numbers fewer than two and a half ­million.

Among ­non-­Christians, the most numerous groups are five and a quarter million Jews and somewhere between three and six million Muslims (the actual figure is a matter of bitter dispute). Since the Census Bureau does not ask about religion, and defining membership is often tricky, all statistics remain open to question. In the world as a whole there are thought to be well over two billion Christians, a billion and a third Muslims, and close to 900 million ­Hindus.

On virtually every point at issue between secular liberalism and Christian ­traditionalism—­prayer in the schools, Darwin in the classroom, homosexuality, abortion, euthanasia, stem cell research, the equal value of all religious practices provided they offend no social ­orthodoxy—­mainline American religion chooses the secular side. Frequently, it makes a proud point of doing so. Last year a network of progressive clergy proclaimed February 12, Charles Darwin’s birthday, “Evolution Sunday,” an occasion for services celebrating the scientific discovery that probably did more than any other event in intellectual history to undermine Christian ­belief.

The fact that mainline religion views traditional beliefs with such distaste may be one reason for its dramatic decline in numbers and influence as the historically Protestant elite fragmented and lost much of its religiosity in the process. Today, elite American opinion, whether nominally religious or not, overwhelmingly backs the secular positions in the controversies mentioned above. It could even be argued that the priority of the secular is implicit in George Washington’s ideal of free religions that give the government “on all occasions their effectual support.” Religious freedom in a pluralistic society, according to this tradition, means subordinating the demands of religious conscience to secular laws or values whenever the religious and the secular collide in the public square. Except on rare occasions, mainline Protestant churches in the United States and western Europe embrace this understanding of priorities almost by instinct, while sometimes (like their adversaries on the Right) claiming a religious basis for what are essentially secular political positions.

Secular values are open to change and interpretation, of course, and at the moment their relation to religious ones may well be in transition. Large majorities of ordinary Americans consistently support prayer in public schools, the teaching of creationism alongside evolution, and related positions that  are scorned as backward prejudices by the mainstream press, Hollywood, most people who teach in universities, and many Democrats. To put it mildly, there is a considerable gap between elite and popular attitudes. In a phrase that became notorious, a Washington Post reporter in 1993 contemptuously described members of the Christian Coalition as “largely poor, uneducated, and easy to command.” The Post subsequently apologized, but similar judgments about evangelical Christians are more than commonplace in the news and entertainment ­media.

It goes without saying that religious institutions also evolve over time. Yet the liberal Protestantism that came to be defined as the American mainstream, with its emphasis on innocuousness and respectability over clarity, has a remarkably long and stable history. In The ­Non-­Religion of the Future (1887), a classic in the sociology of religion, ­Jean-­Marie Guyau declared that “Protestantism is the only religion, in the Occident at least, in which it is possible for one to become an atheist unawares and without having done oneself the shadow of a violence in the process.” He went ­on:

According to the new Protestants there is no longer any reason for taking anything at its face value, not even what has hitherto been considered as the spirit of Christianity. For the most logical of them, the Bible is scarcely more than a book like another; one may find God in it if one seeks Him there, because one may find God anywhere and put Him there, if by chance He be really not there already. . . . God no longer talks to us by a single voice, but by all the voices of the universe, and it is in the midst of the great concert of nature that we must seize and distinguish the veritable Word. All is symbolic except God, who is the eternal ­truth.

Well, and why stop at God? . . . Why should not God Himself be a symbol? What is this mysterious Being, after all, but a popular personification of the divine or even of ideal humanity; in a word, of ­morality?

It is hard to imagine that such a ­watered-­down set of beliefs might not be reconcilable with modern science, with feminism, with practically any dominant secular ­trend.

Yet the illusion that all conflicts can be finessed by taking the traditional claims of faith in a figurative or metaphorical sense can itself become a source of conflict. (Nobody ever argues that physics or biology should be taken figuratively.) When elite opinion insists patronizingly that there is no real contradiction between the conviction that a benevolent, omnipotent God created humanity in his own image and the scientific picture of a chancy, aimless, indescribably brutal process of evolution by random mutation and natural selection, one need not be a fundamentalist to feel skeptical. Polls over many years indicate, to the consternation of scientists and many pundits, that only a minority of Americans accept evolution as biologists understand it. Hence the surface plausibility of the majority opinion that intelligent design or some other variant of creationism should be available in schools as an alternative to naturalistic ­evolution.

Equal time for competing doctrines is such an established principle of American life that those who argue against it in this instance are inevitably at a rhetorical disadvantage. The endlessly repeated liberal mantra that “science” is fully compatible with “religion” never quite persuades most of the 90-plus percent of Americans who tell pollsters they believe in a god because that mantra  ignores too many of the convictions central even to ­non-­fundamentalist forms of religion. On this point, ironically, atheists and biblical literalists are in perfect ­agreement.

Despite their intellectual evasions, or maybe because of them, American forms of religious tolerance have served the nation well most of the time, and still do. Even among the most devout, few of us would wish to see a state religion, let alone the scale of animosities that Washington congratulated the United States for avoiding. Not surprisingly, the level of mutual irritation has increased along with the power of the state over education and ­once-­private ­relations—­the public square has grown much larger than it was in Washington’s ­day—­but by any historical standard we still manage these things impressively. What other large country today is doing it as well? Every American is legally free to insult every other American’s beliefs, yet the conflicts are less destructive than in most countries where the law protects believers from offensive speech. Of course, it helps that American religion is so fragmented, and that the vast majority of us (unlike, say, Wahhabi Muslims of the present or European Calvinists of four centuries ago) do not consider faith our strongest ­allegiance.

The complicated attitudes of believing Americans toward other religions and the state add up to a series of paradoxes that often annoy their secular compatriots and bewilder foreigners. The United States currently has a president who is more overtly religious than most of his recent predecessors, and his faith unmistakably affects his view of some public issues. At the same time, he goes out of his way to express an impeccable tolerance toward other ­religions—­especially the acid test of Islam since 9/11—and even toward unbelievers. This mixture of aggressive religiosity with deference toward the opinions of others strikes much of the world as incomprehensible. Perhaps it is merely American. President Dwight D. Eisenhower expressed it in its most endearingly nebulous form: “Our government makes no sense unless it is founded on a deeply held religious ­belief—­and I don’t care what it is.”

While this sublime formula helps explain some of the deepest paradoxes of American life, it seems not to export well. Much of the world operates on quite different assumptions. Serious religion has its own agendas, on which inclusiveness and social harmony sometimes rank far down the list. Obeying the Lord’s commands may loom larger. Where those commands involve public controversies, the effects can be spectacularly disruptive even in an open society, whether the crusade is to end segregation or outlaw abortion. A powerful and incomparably destructive form of contemporary religion still mandates religious terrorism, the indiscriminate killing of Jews, Crusaders, apostates, and often the worshiper himself, as a matter of conscience. Like other major faiths, Islam has contradictory teachings about militancy and tolerance, individual autonomy and the social order, peace and the sword. How far other forces of ­history—­science, political change, the failure of militant Islam to achieve its goals, or (as eventually happened in Europe) sheer ­exhaustion—­may eventually work to sheath the sword of faith is a crucial question for this young ­century.

So far, the search by outsiders for a critical mass of “moderate” Muslims in the image of mainline Christians, either in the Islamic world itself or in secular Europe, has led only to repeated disappointments. After an obsessively analyzed succession of terrorist events, threats, riots, and murders, European countries find themselves at a complete loss about how to integrate a large, growing, and frequently alienated Muslim population. Affluence and technological advance, it seems, will not automatically bring about a decline in religious commitment. They may actually be stimulating its most fanatical forms. Meanwhile, public opinion in such countries as Denmark and the Netherlands becomes increasingly frustrated. Negative popular attitudes toward Islam are often dismissed as racism, but confronting militant beliefs is quite different from expressing racial prejudice. Instead of the future of the planet, ­post-­Christian western Europe may represent an exception as extreme in its own way as theocratic Iran or Saudi Arabia. As a British Muslim told a columnist for The Guardian in the wake of the July 7, 2005, London terrorist bombings, the fact that you no longer believe in your religion is no reason we shouldn’t believe in ­ours.

One reason Muslim immigrants may have an easier time integrating into American society is that piety of almost any sort is so much more common and accepted here than in Europe. The complete secularization many intellectuals have been yearning for since the Enlightenment, now nearly achieved in Europe, turns out to bring its own set of unexpected problems. Although George Washington would no doubt be disappointed, an American future of emotional, ­never-­quite-­settled conflicts over the place of faith in public life looks like an acceptable price to pay for avoiding the far greater evils that afflict both the devout and godless regions of the ­earth.