Wars have been fought over its differences. And, along with politics, it is one of two things we don't talk about at parties.
Unless it is an NFL party, and then we go to war talking about it.
Football has always been a religion to some. But now, thanks to Denver Broncos quarterback Tim Tebow, sports and religion have become the topic du jour.
Arguments over Tebow's path to the Hall of Fame can be waged. But he is surely the only proper noun (Tebow) that can become a verb (Tebowing) by dropping to one knee.
"Tim is who he is," said Brent High, associate director of athletics for spiritual formation at Lipscomb University, where an event sold out when Tebow spoke there. "If you are a Christian, he is your absolute flag-bearer in the sports world. You cheer for him and you hurt for him when he takes the beating that he takes." But ...
"If I am putting myself in the shoes of someone who is offended ... and Tebow is getting down on one knee with all cameras trained on him, that's in my face. ... So I can see why it's like the fingernails on the chalkboard to those people."
Tebow's actions aren't new.
Athletes have been thanking God longer than they have been thanking mom. Fans have pledged loyalty to a higher being in exchange for a touchdown, a first down or a fumble.
After the Penn State scandal broke and before the Nebraska game, the Nittany Lions knelt in prayer with their opponents.
Before Tebow, there was quarterback Kurt Warner thanking Jesus after a Super Bowl win.
"We've had athletes being very vocal about their faith and using their status as athletes to promote their faith for a long time," said Tom Krattenmaker, author of "Onward Christian Athletes: Turning Ballparks into Pulpits and Players into Preachers."
"This dates back to World War II when you saw organizations that were all about using the popularity of big-time spectator sports as a platform for promoting the faith. ... But Tebow seems to have taken it to an extra level of intensity."
Others show their faith
Tebow doesn't have a monopoly on sharing his faith through the spotlight sports brings. Free agent first baseman Albert Pujols points skyward with both index fingers when he crosses home plate. All-Star Oklahoma City forward Kevin Durant has been spotted reading the Bible at his locker before games. Florida Panthers 2011 second-round draft pick Rocco Grimaldi tweets Bible verses. An invocation is given before the "Gentlemen, start your engines!" command at many motor sports events, including NASCAR.
"I often think about the same thing," says Patton Dodd, managing editor at Patheos, a website that is dedicated to religion and spirituality, and author of "The Tebow Mystique." "I often think about Troy Polamalu, who you will hear Pittsburgh Steelers players say is the most religious athlete in football. He crosses himself before every play and sometimes after. He prays during plays. It is odd that there are more outspoken Christians on the Broncos, like Brian Dawkins."
But Christians don't have a stranglehold on sports.
Muhammad Ali, a Muslim, showed that even the war-sports-religion combo is nothing new. He gave up a heavyweight title for that trinity when he was arrested and found guilty of draft evasion in 1967.
Esquire writer Scott Raab, author of "The Whore of Akron: One Man's Search for the Soul of LeBron James," about James leaving the Cleveland Cavaliers, says: "I've never been able to un-intwine" being Jewish and a suffering Cleveland fan. When approached with the theory that maybe fans sold their soul to get Jim Brown and an NFL title in 1964 — the last major pro title won by a Cleveland team — he clings to that.