Imam Feisal Abdul Rauf, founder of the American Society for Muslim Advancement, tells Walters he believes heaven is indeed a physical place, but getting there depends on your behavior in this life. "The real life is the next life … and based upon how we live this life, it determines where we shall be in the next. We are told we will be in comfortable homes, reclining on silk couches … so we're given the delights of sex, the delights of wine, the delights of food with all of their positive things without their negative aspects."
The promise of heaven plays a central role in the life of evangelical Pastor Joel Osteen.
America's evangelicals see themselves as the purist version of the faith, with a God-given mission to save the world.
These days, they are more influential than ever. Osteen's televised sermons attract about 7 million viewers on Sunday mornings, and 36,000 evangelicals pack his Lakewood church in Houston every week, the largest weekly religious gathering in the country.
Evangelicals believe that a person can get to heaven only if he or she believes in Christ and if he or she is born again. So what happens to everyone else?
"I think only God can be the judge of that," Osteen said. "I can't be the judge of other people. … The Christian faith shows us that Christ's forgiveness is available to anybody. All we have to do is call on the name of the Lord. … I don't think there's any guarantee in the Scripture that we [go to heaven] if we do not have a relationship with Christ."
Rabbi Neil Gillman, a professor of philosophy at New York's Jewish Theological Seminary, expresses Judaism's perspective on the afterlife. "For the past 2,000 years, most Jews believed that at death, the body and the soul separate, the body is interred and disintegrates in the earth, the soul goes off to be with God," he tells Walters. But that's not the end of the story. "At the end of days, God will resurrect bodies, will reunite body and soul, and the individual will come before God to account for his or her life," Gillman says.
Walters also speaks with scientists who say they're beginning to understand why so many people believe in heaven. Still, they have yet to come up with any proof that it exists.
For most people, proof of heaven's existence is not necessary. Faith is all they need. Dr. Dean Hamer, a geneticist at the National Institutes of Health, thinks he has figured out why this faith comes easily to some, but eludes others. "Whether a person is spiritual or not is not necessarily a matter of their will. It may be something innate about their personality," Hamer says.
Hamer suspects spirituality might be a personality trait encoded in our genes. He began his research by asking more than 1,000 people to answer a series of questions about faith and spirituality. He then tested DNA from the study participants and found that those who scored highest on his survey had a mutation of at least one gene that seemed to affect their level of spirituality. He named it "the God gene."
"It's a gene that's called VMAT2 and we can isolate it, and we can study it in detail. … This particular gene controls certain chemicals in the brain. And those chemicals affect how consciousness works. They affect the way that our feelings react to the events around us," he says.
Hamer also notes that researchers have been able to detect changes in the brain when people are in the midst of intense prayer or meditation.