Bob Noyce, Deseret Morning News

At one level, the difference between a theist and atheist is simply a small gap of white space. But the divide between the two is also a chasm, a difference not just about sect and doctrine, or church vs. state, but about fundamental questions of the origin and purpose of life.

Not surprisingly, the two camps rarely try to understand each other — although in America they generally tend to live and work side by side without blowing each other up.

And so, on a recent afternoon, David Keller and Mark Hausam sat at a table in a downtown restaurant talking civilly about their upcoming debate entitled, "Does God Exist?" The debate, sponsored by Forum for Questioning Minds, takes place at 2 p.m. Sunday in the auditorium of the Salt Lake City Main Library, 210 E. 400 South. In a season of debates about candidates and school vouchers, in a city that is the headquarters of an international religion, "Does God Exist?" is perhaps the most audacious debate of the lot.

To Keller, an associate professor of philosophy at Utah Valley State College and director of the school's Center for the Study of Ethics, believing in God is an irrational act. For Hausam, adjunct philosophy instructor at Salt Lake Community College and an elder at Christ Presbyterian Church in Magna, nothing about the universe or human existence can be explained without God.

They met to talk about the debate's ground rules with moderator Deen Chatterjee, an associate professor of philosophy at the University of Utah. Chatterjee doesn't want some kind of namby-pamby discussion in which, for example, Keller just pokes some holes in Hausam's position. "To prove God doesn't exist," he cautions Keller, "you have to come up with separate arguments. You have to go beyond just saying, 'Mark can't prove God exists."'

The last time the Forum for Questioning Minds had a similar debate — about whether morality depends on God, also featuring Hausam and Keller — it drew a standing-room-only crowd. People were lined up at the audience microphone long after the debate was supposed to have ended.

The Forum draws well-informed, intelligent, mature adults, Chatterjee says. "Most have gone through their share of critical inquiry their whole lives. Some are humanists, and some are atheists."

"A theist gets thrown into the den," says Hausam with a wry smile.

Well, says Chatterjee, the debate probably also will draw lots of people from area churches. And many of the Questioning Mind folks would probably agree there is some form of "higher power or intelligence," he says.

But for the purpose of this debate, the three philosophers decide, "God" will mean an Abrahamic God, a personal, anthropomorphic God, a "who" rather than a "what," a God who cares about humans, not just a creative force that may have set the universe in motion. Because Chatterjee, Keller and Hausam are philosophers, the debate will focus on arguments based on "reason" rather than those based on "faith." But they'll try not to throw around words like "epistemological."

Each debater will get 15 minutes to sum up his position, distilling centuries of arguments — from Thomas Aquinas' "Summa Theologica" to Richard Dawkins' "The God Delusion" — in what they hope is the most convincing proof, yea or nay.

Keller says he doesn't feel comfortable arguing categorically that he can prove God doesn't exist. How about if he just says "the vast preponderance of evidence rules against the existence of God"? It sounds so arrogant to proclaim that he knows for sure one way or the other, he says. "I'd have to have an almost God-like omniscience."

Chatterjee is clearly disappointed. "That leaves people clamoring for more," he says.

The three men talk about the difference between "reasonable" and "rational." "Lots of things that are irrational we hold onto, because they're reasonable," Chatterjee says, offering the example of Santa Claus. To show that believing in God is reasonable, he tells Mark, isn't good enough. "Your task is to show, based on evidence and reason, that it's rational to say that God exists."

Chatterjee grew up without any religion. "I'm still searching," he says. Hausam is an orthodox Presbyterian. Keller is descended from Mormon pioneers who came across the Plains with Brigham Young. He first began to question his religion as a teenager, when he noticed "that there was a striking dissimilarity between the way my peers and the people I observed behaved during the week and on Sunday." That disconnect between religion and ethics led in subsequent decades to the study of "all the arguments for the existence of God by all the great Christian philosophers, which I found to be incredibly fallacious."

"I think people like Mark should be intellectually honest and say, 'I believe in God, and it's not rational,"' he says. "If there really was a God-like being, I would be happy to accept that, because I want the truth. That's what led me down the path to atheism. If there is a God, I want evidence. I want good arguments, and they don't exist."

Hausam's arguments, in short, begin with First Cause, i.e. "Nothing comes from nothing. Without some kind of cause, you don't have anything just popping into existence from nowhere." And this First Cause would have certain characteristics that require it to be "unbounded by time and space." God, he will argue at the debate, is "a person, a mind." To explain human thought and love, he says, requires a First Cause that includes consciousness.

But to argue that the origin of consciousness must be God, Keller counters, "is based on a flawed notion of nature." Among the arguments he will put forth will be his assertion that "mentality and psychological properties as we know them are an intrinsic component of nature," that there are inherent properties in nature itself that are creative and self-organizing, and it's those properties that produce consciousness.

Neither Hausam nor Keller is looking for "converts." Hausam figures that the Forum for Questioning Minds will be a tough crowd, and if he just breaks down some barriers he'll be happy, he says. "I want them to see that theism isn't as crazily absurd as they think it is — to at least consider it."

The goal, says Chatterjee, is to get people to civilly discuss fundamental issues, to show that in America we can come together and talk things out. "The goal is not to have a clear victor," he says, but to get people to really think about their preconceived notions, whatever those might be.

To which Hausam looks up from his sandwich and deadpans: "I was going to say 'amen,' but I didn't know if it was appropriate."