"In God We Trust" is right there on all our coins and currency. To find the phrase "Wall of Separation," however, you must go not to the Constitution or the Bill of Rights, but to a letter President Thomas Jefferson wrote to Connecticut Baptists in 1802. His words have guided us ever since, but what, in practical terms, do they mean? Our Cover Story is reported now by Martha Teichner:
Eleven days and counting before their state nominating caucuses, it's understandable that some Iowa Republicans may be having trouble separating politics and religion.
The battle between, the Mormon, and , the Baptist preacher, has defined the race.
But even the possibility that a candidate's brand of faith could become a kind of presidential litmus test worries as many, if not more, Americans than it reassures - among them, Jon Meacham, editor of Newsweek.
"We are veering very close to violating the article in the Constitution that says, there should be no religious test for federal office," Meacham told Teichner.
Meacham is the author of "American Gospel," an attempt to put the tension between God and politics in historical perspective.
"You have 46% of Evangelicals, in a poll that Newsweek did in Iowa, saying that Romney's Mormonism makes them less likely to vote for him," said Meacham. "That, in and of itself, is a very dangerous battle to have because it pushes religious affiliation to the center of debate in a country that has done very well when it has kept that kind of religious debate to the sides, or off the table altogether."
The living embodiment of that notion of separation is the neighborhood of Flushing, in the New York City borough of Queens.
Here you'll find every nationality imaginable - every religion. Within a few blocks, there are churches, a Quaker meeting house, Buddhist temples, synagogues, a mosque. As a sign of how mixed-up everything is, in front of the Queens public library, the Christmas tree and the Menorah were sponsored by the Chinese Businessmen's Association."
Professor Kenneth Jackson, who teaches New York history at Columbia University, described the significance of the remonstrance:
"This is one of the really great documents of American history that's preserved by the archives. It's the first thing that we have in writing in the United States where a group of citizens attests on paper and over their signature the right of the people to follow their own conscience with regard to God - and the inability of government, or the illegality of government, to interfere with that."
In 1657, Flushing was a farm village, and like Manhattan, part of New Netherland, a Dutch colony governed by Peter Stuyvesant. Stuyvesant persecuted followers of religions other than his own Dutch Reformed Church. When he barred Quakers from Flushing, thirty local citizens, none of them Quakers themselves, petitioned Stuyvesant, claiming the ban violated Dutch custom.
"It's just elegantly and eloquently written," Jackson said. "They say, 'We desire, therefore, in this case, not to be judged, least we be judged. Neither to condemn, lest we be condemned, but rather let every man stand and fall to his master.'"
Peter Stuyvesant, no man to be trifled with, fined the petitioners and threw them in prison until they recanted - but there's more.
An important part of this story is the role played by a man named John Bowne, who lived here. Bowne allowed the Quakers to meet in his home. He was arrested, jailed, and sent to Holland for trial. The outcome was not what Peter Stuyvesant expected - Bowne was exhonerated.
And the principles set forth in the Flushing Remonstrance - essentially, freedom of worship and the separation of church and state - became practice.
"It didn't just come out of thin air, the First Amendment to the Constitution. We believed this already, in 1791, so it could become the cornerstone of the Bill of Rights," Jackson said.
Remember, most of the original 13 colonies had established churches and actually taxed citizens to support them. The end of that led to an explosion of religious fervor.
"In other words," Teichner asked Jon Meacham, "the separation of church and state enables the tolerance of someone else's religion?"
"Absolutely," Meacham agreed. "The separation of church and state is like oxygen to the fire of religious liberty."
So if you thought the tug-of-war between religion and politics is something new, think again.
"Religion has always been a weapon in the political arena," Meacham explained. "In 1800, there were advertisements that said you could have Jefferson and no God … or Adams and God."