U.S. politics has been filled with moral crusades, a fact that many Americans and probably even more Europeans do not appreciate. Some Americans have denounced the 2004 presidential election on the ground that it was won by a candidate who sought to impose religious intolerance on a free nation. Newspapers such as the Daily Mirror have accused most Americans of being dumb.

The truth is that although religious values played a role in the election, so did the war in Iraq, the threat of terrorism, the condition of the economy and the integrity of the two candidates. There is not a shred of evidence that the winning candidate waged a moral crusade. Neither abortion nor school prayer was a campaign issue. President Bush and John Kerry agreed in their opposition to gay marriage.

Both candidates made it plain that, though religion was important to them, they had no desire to draw from that religion anything more than personal strength.

Neither wanted to impose his beliefs on others.

Nevertheless American political history has been filled with religious crusades.

In the early 19th century, prohibition against the sale of alcohol became an issue, leading Maine to ban its distribution. This prompted John Stuart Mill to write On Liberty in which he argued against the policy. In time prohibition became a national law, finally abandoned in 1933.

The struggle against slavery was first and foremost a moral struggle. The 19th-century religious revival, the Second Great Awakening, helped to fuel the anti-slavery movement and inspired countless preachers to denounce the captivity of blacks in intense biblical language. The Civil War, at first fought to preserve the Union, was ultimately transformed into a war designed to free blacks. The postwar Reconstruction was deeply moulded by a moral commitment to individual freedom.

The Civil Rights movement was in part an effort to extend the existing protections of the Constitution to those who had been denied the right to vote or to take any seat on a bus or train. But beneath this legal effort was a powerful religious effort to do more than equalise voting rights or make bus seats available. It was an effort to redefine the relationship between the races that was inspired by evangelical teachings about the dignity of the individual before God. It is no accident that a minister, Martin Luther King, was the hero of this movement.

The concern about abortion and school prayer have religious roots though these were not much in play in the last election. At first a few opponents of abortion attacked clinics and besieged (and in some cases murdered) doctors who performed abortions. But most of that has passed into history. Today the right-to-life movement relies on legal and practical arguments.

Many Europeans must wonder why religion has been so important in American politics. The Constitution says next to nothing about the matter except to ban religious tests as a qualification for holding office. Many of the architects of the U.S. constitutional system were, at most, deists who agreed with Thomas Jefferson when he wrote of "Nature's God" rather than of a personal God in composing the Declaration of Independence.

Moreover, the First Amendment to the Constitution guarantees the free exercise of religion and prohibits any law "respecting an establishment of religion". Since the middle of the 20th century, the Supreme Court has generally enforced these provisions stringently. And yet we hear on all sides complaints about America's insane religiosity.

Our English friends must be especially perplexed, since you have developed a political system that acknowledges religion without making it an instrument of national policy. The Prime Minister appoints the Archbishop of Canterbury but no one thinks that this means that the Archbishop will help to make government rules.

Much of Northern Europe is intensely secular, and even in Southern Europe churches are losing the faithful.

In the U.S., by contrast, evangelical sects are growing rapidly even as mainstream Protestant denominations are losing members. Though the Moral Majority movement has collapsed because of its heavy-handed methods, fundamentalist Christian groups are active in politics.

The traditional social science argument that modernisation implies secularisation may be true in Europe, but not in the United States (or in much of Africa and Latin America). In economics and technology, America may be the most modern country in the world, but it is also among the most religious. Why?

The answer, I think, was given by Adam Smith more than 200 years ago. He suggested that if a political system never endorsed a religion, it would tend to deal "equally and impartially with all the different sects" resulting in a "great multitude" of them. Each religious leader, like every business in a competitive economy, would be induced to use "every art both to preserve and increase the number of his disciples". With two or three hundred sects, the public order would be secure because no one could disturb it. Or as Voltaire put it, with one Church you have tyranny, with two civil war, but with a hundred peace.

America has countless sects. As a result it has religious freedom. Those who say otherwise are imagining a world that does not exist.

James Q. Wilson is chairman of AEI's Council of Academic Advisers.