Why are Kirk Cameron, a preacher, and two self-proclaimed atheists coming together in a church this weekend? Because Cameron and preacher Ray Comfort claim that they "can prove the existence of God."
They'll take on the atheists in the first "Nightline Face-Off," a debate to be moderated by "Nightline" anchor Martin Bashir.
Watch the Face-Off Wednesday May 9 at 2 p.m. on ABC News Now, and on Nightline at 11:35 p.m.
As Mike Seaver, the oldest son in the smash hit sitcom "Growing Pains," actor Kirk Cameron could make audiences roll with laughter. But now he wants to bring them to the Lord. And he's deadly serious.
In March 2006, "Nightline" profiled the Way of the Master, a Christian ministry headed by Cameron and itinerant preacher Ray Comfort. Operating as a charitable trust, its intention is to educate and equip the church to preach the message of Christianity to nonbelievers. Cameron says he is motivated by a literal fear of hell.
"I believe the Scriptures teach that there's a literal heaven and a literal hell, just like Jesus said," he explained. "And without forgiveness of sins that, yeah, the place of punishment is called hell."
The Way of the Master has a weekly television show for which Comfort and Cameron literally hit the streets in the name of Jesus, challenging nonbelievers that their sins against God will lead directly to hell.
"On the Day of Judgment," Comfort tells one man on the streets of New York, "God will see you as a lying, thieving, blasphemous, adulterer at heart. You have sinned against God. You need his forgiveness."
On occasions, things go badly wrong and the pair are attacked by members of the public. Comfort recalled one incident, saying, "While I was preaching the Gospel a gentleman came up and he started spitting on me. And he spat quite a few times." Comfort says he simply remained calm and moved on.
Neither Comfort nor Cameron has theological degrees nor any kind of formal training. But Cameron says he's convinced his new career is vitally important.
"I have no authority. I am simply trying to be faithful to the God who saved me, who changed me and who has commissioned me to tell you and those who are watching this interview … about the Gospel of Jesus Christ and that it has the power to change people's hearts."
"There isn't any good reason to believe in God," so says Brian Sapient, a member of the Rational Response Squad, a group of atheists "Nightline" profiled in January.
What's wrong with God? "What's wrong with the tooth fairy?" asks Brian. "There's nothing wrong with something that most likely doesn't exist."
"Atheists are completely vilified. And it's OK," says Kelly, an atheist who works alongside Brian and also asks that her last name not be used.
"It's actually OK to hate atheists," Kelly says. "We are like the last group that people overwhelmingly agree it's OK to hate, because there's an absurd caricature of atheism out there."
While their theological views differ from the Way of the Master, their approaches are similar -- brash and in-your-face. The Rational Response Squad challenges people to take the Blasphemy Challenge in which they make videos of themselves denouncing or blaspheming the Holy Spirit, and then post them on YouTube.