Hall's freshman drama, airing Friday, Feb. 27, on CBS, is proving one of the few hits of the 2003-2004 season.
That probably comes as a surprise to those who first heard the show's concept when it was originally picked up. Amber Tamblyn ("General Hospital") stars as Joan Girardi, an ordinary teen visited by God, who appears in the guises of various people. God gives Joan tasks, which she performs -- sometimes eagerly, but more often reluctantly -- usually with unexpected results. Along the way, she learns more about her own nature, her friends and family, and the changing circumstances of life.
"I always knew that people were going to think 'This is the worst idea ever,'" Hall says. "I was always aware of that. I confronted all that and decided my job was to write it and not worry about anything else. I literally can't control what happens."
Over the show's run, Hall has heard a wide range of questions about God, both from believers and non-believers. One of the most frequent ones is, "If there is a God, why do bad things still happen?"
"I love that one," she says. "That is a very, very complicated theological discussion that I won't have with people who won't learn theology. It's a question for someone who's stopped exploring theology. My thing is always, I was that person for a while, then I got the point where, maybe you have to believe that you will come to understand. That is actually the cornerstone of my belief."
Just the concept of writing -- in this case, a TV show about God -- intrigues Hall.
"I do believe in the act of co-creation. We created everything we have. There has to be a reason that we are like that. There has to be a reason that we are able to create, not just procreate. Monkeys don't write poetry.
"And music is a kind of language. My thing is always music. I'm a musician. There's something that happens in the creation of music that is so sublime and mysterious to me that I can always go there."
Raised Protestant and now a practicing Roman Catholic, Hall has featured a priest on the show a few times, along with a rabbi. But she has stayed away from pushing Joan toward one organized religion or another.
"I'm doing as much of that as I want to do now," she says. "But I want to do more because I'm fascinated by world religions. I never ever wanted to do a show about God that didn't deal with religion. I always felt I wasn't going to take a particular stand. I wasn't going to say, 'This is the right religion' on the show, but I wanted people to look at world religions. I find it so fascinating. I want to do more.
"My whole thing is, I'm really not trying to bring anyone with me, because I know how I arrived at my own spiritual beliefs was such an incredibly long and complex journey that I almost can't explain it."
While some people settle firmly on religious beliefs early in life and stick with them, Hall says, "They must not have had much fun along the way. You would have to have been sitting in your living room [the whole time]. I don't envy them. I've seen a lot of difficult things because I've lived a really big life, and that's my intention.
"I'm always telling my daughter, 'If you learn to play an instrument, you're going to hear some bad sounds.' That's how I feel about life. If you're going to do this, you're going to see some bad things. If you protect yourself from engaging life -- maybe not."
That's part of the reason why Hall chose to make the character of Joan's father, Will Girardi (Joe Mantegna), a police officer.
"I wanted a man who was a good man," she says, "who had a really strong sense of right and wrong, and dealt in a world where he literally had to look at good and evil. There was a literal physical fight between good and evil, and he had to look at it. He had a strong sense of morality, and it didn't come from religion. I wanted that world bumping up against a very, very spiritual world.
"My thing is always he's the physical warrior; she's the metaphysical warrior. I don't know how much Joan's interaction with God would mean if we weren't seen a world more like the one we live in, where you have to look at really awful things. The whole point was to contend with God in a world where things are really awful, like 9/11. I've never been interested in God in a benign universe."
It's been hard for critics to find a label to put on "Joan of Arcadia." You can call it "spiritual drama" or "family drama" or even just "drama." But Hall would prefer that you don't call it "fantasy," stating firmly, "There's no fantasy on this show."