Perhaps the most famous secret society is the Freemasons, a medieval guild of stonemasons that formed in England in the early 18th century and developed into a powerful fraternity.
The Freemasons have enjoyed a reputation as influential politicians, scientists, and artists whose works and charities have enhanced the world. Some Christian leaders, however, have called it a secret society bent on spreading evil.
Of the 55 men who signed the Declaration of Independence, at least 9 are said to have been Freemasons. President George Washington was also among its members.
In the new movie the Freemasons are seen in a positive light.
"The Masons were founded on pretty solid principles, and a lot of those held for the Founding Fathers and probably influenced them a great deal toward democracy at the time," said Kouf, whose grandfather was a Freemason. "When Washington had trouble raising his army, he called upon his Masonic brothers, because he knew he could count on them."
There is a tenuous link between the Freemasons and the Knights Templar, a mysterious order of knights founded in 1119 to protect Christian pilgrims on their way to the Holy Land. Many Freemasons today say they are the spiritual descendants of the knights.
According to legend, the Knights Templar discovered the greatest treasure in human history buried beneath the Temple of Solomon in Jerusalem. What is true, scholars say, is that the knights became wealthy and powerful, and they may have rivaled the influence of some European kings.
"They're mysterious because they were so sensationally successful," said Lisa Bitel, a history professor at the University of Southern California, Los Angeles. "The idea behind lots of these conspiracy and treasure stories is that any individual could happen upon a forgotten relic of the past, join with other like-minded mavericks, and use this relic for personal redemption or universal good."
But in the early 1300s, the knights were suppressed and executed. Whether they found Solomon's treasure is not known. No treasure map has ever been found.
Spoiler warning: Do not read on if you prefer not to learn a key plot development in the The Da Vinci Code.
Although the medieval knights also feature prominently in The Da Vinci Code, it was that novel's main plot twistthat Jesus Christ married Mary Magdalenewhich stirred up real controversy. Could this be true?
"There's no evidence for it in any text," said Joseph Kelly, a professor of religious studies at John Carroll University in Cleveland, Ohio, who has given numerous public lectures disproving the "secrets" in Brown's novel.
Kelly says many people are disappointed when he tells them that the marriage never happened. Yet the academic says there are many things in the book that are historically accurate, and he believes the novel serves a valuable purpose.
"Brown tells people something they never knewthat the early history of Christianity was much more complicated than anybody thought," he said.
Kouf, the movie scribe, sees little danger in weaving together fiction and history.
"If we were laying it out as a true story, then I'd agree that we're taking too many liberties," he said. "But because it's set out in an adventure mold like Indiana Jones, I think we're OK. People know some of this stuff didn't happen."
Still, Kouf, who considers himself a "history nut," said he tried to include as many references to U.S. historyand use as many real locationsas possible.
"Mostly we set out to have a rollicking good time," he said. "But if it gets people to also look at history differently and pick up a book about the Founding Fathers, that's great."
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