February 18 is Presidents Day in the United States. It's a day Americans have set aside to honor past presidents and to examine their legacy and significance. One of the most intriguing aspects of this group of men is the degree to which religion has played a role in their leadership. VOA's Adam Phillips has more.

When it comes to religion, Americans tend to see the Founding Fathers in one of two stereotyped ways: either as pious churchgoing folk with Jesus and the Bible firmly at the helm, or as cool scientific rationalists who thought that Man could govern himself quite well without God anywhere in the picture.

In fact, most of the Founding Fathers and early presidents were Deists. Deism was a sophisticated 18th century religious philosophy that inferred the existence and nature of God based solely on reason and personal experience, not from faith as such.

"They believed in God, a benevolent god," Professor Gary Wills, the eminent American historian and Pulitzer Prize-winning author of nearly 40 books, explains. "They believed in Providence. In fact, that was their name for God, often. That's what George Washington called 'God' ? 'Providence.'"

"[The Founding Fathers] didn't believe that Jesus was divine. They thought he was a great moral teacher," says Wills. "They didn't believe in the efficacy of prayer. They thought 'God doesn't need our advice.' "

Among the many radical features of the U.S. Constitution, ratified in 1787, was an amendment creating a formal separation between church and state. It was strongly supported by Thomas Jefferson and James Madison, who would become America's third and fourth president respectively. They saw it as a way to protect America's various religious denominations from domination by government power and ideology. They also believed individual conscience to be the supreme and final judge in spiritual and moral matters.

Wills says that this view made both men even more radical than the British political philosopher John Locke, who had advocated mere tolerance by the government of diverse religious beliefs. "They said 'No, no! Tolerance is 'top-down.' It means the authorities can tolerate you and it's up to their discretion. We should have it 'bottom-up.' That it's the right of the individual conscience that can't be coerced [and] that is the supreme judge on these matters.' That was their starting point."

Most educated 19th century Americans were well-versed in the Bible, even if, like Abraham Lincoln, they were not especially religious. According to Wills, when Lincoln took office in 1861, just before the Civil War, he had been a skeptic most of his life, and was probably an atheist in his youth.

"But as he went on," Will says, "he became more profoundly religious. He had a much more Jewish concept of the whole people being the people of God, sinning as a people, being saved as a people, repenting as a people."

During the nation's first century, several presidents had proclaimed national Fast Days in order to turn the nation inward, and elicit divine sympathy for a cause. James Madison proclaimed one during the War of 1812. During one of the darkest periods of the Civil War, Lincoln proclaimed a National Fast Day.

"But he did it in a way that no other person had done," Wills says. "Instead of ratcheting up animosity, building up bellicosity, he ratcheted it down. He said in war 'everybody does things wrong. Every war has pillage and rape and senseless killing. And it's true of this war.'"

Wills calls Lincoln's Fast Day Proclamation "a proclamation of repentance. It was an amazing act of leadership we haven't seen in other presidencies."

While American presidents are required to remain technically neutral in matters of religion, the American people are not. In 1960, many were openly troubled by presidential-hopeful John Kennedy's Catholicism. They feared his loyalties might be divided between Catholic Doctrine and America's Constitution. Kennedy said he'd resign if the two ever did conflict.

But Gary Wills, a religious Catholic himself, says presidents can easily avoid such dilemmas: they must separate their religious motivation for favoring a policy from the secular arguments they make to convince others to adopt it.

"For instance, a Christian who believes the gospel hears Jesus say 'Whatever you did to the least of my brothers, you did to me.' [So,] love of Jesus is our motive for being good to the poor," Wills explains. "But we can't make that the state's motive." Instead, Wills says, "What we have to do with them is say 'it's just. It's a matter of human dignity to treat the poor well.' So your motive is not the same thing as your argument."

Even deeply religious presidents have usually respected the line between church and state. Jimmy Carter, for example, an evangelical Baptist who became president in 1977, never held a prayer service inside the White House during his four years in office. In contrast, in the opinion of Gary Wills, George W. Bush, a self-professed born again Christian, has inserted religion into public policy to an unprecedented degree.

Wills says that whatever the religious beliefs of future presidents, the Constitutional wall of separation was designed to be strong enough to preserve America's secular political tradition.