On a stretch of highway 20 near Pell City, Alabama, a billboard instructs drivers to "Imagine no religion." The sign, which is looks like a stained-glass window, accompanies the John Lennon quote with the url for the Freedom From Religion Foundation, a nonprofit group that lobbies to support the separation between church and state. While the message is restrained, it has already inspired a heated public debate.

In the grand scheme of things, it seems odd that the question of whether or not God exists is so controversial. Just as some people go to church and others don't, the dividing line between atheism and belief is largely a private concern, relegated to how people spend their weekends and, to some extent, how they explain their actions. In fact, the battle over which God one worships seems far more likely to result in broken noses and bruised feelings.

However, the Pell City billboard has transformed a private question over God's existence into a very public battle. Initially, the Alabama Freethought Association attempted to install the Lennon billboard near the Birmingham-Shuttlesworth International airport, but was rebuffed by Lamar, the company that controlled the site. The second site, on highway 20, ultimately worked out, but has resulted in irate phone calls and a petition to force its removal.

Signs that endorse Judeo-Christian religions have been part of the American landscape for decades. Recently, however, a growing chorus has pushed for greater inclusion of non-religious messages. Britain's Atheist Bus program led the charge when it placed the slogan "There's Probably No God...Now Stop Worrying and Enjoy Your Life" on 30 London buses. The message was subsequently picked up by similar campaigns in Spain and Canada. In Washington, DC, the American Humanist Association ran bus ads asking "Why believe in a God? Just be good for goodness' sake."

At the same time, several municipalities soundly rejected Atheist ads. Australia, Italy, Croatia, and Switzerland all refused to allow them, as did Bloomington, Indiana and -- thus far -- New York City.

Even in areas where the Atheist ad push has failed, however, the public discussion has inspired a serious -- and energetic -- discussion about community values and the place of religion in society. As Pat Cleveland, a Freethought Association member in Alabama notes, "I'm proud to be an American [...] I'm a good person. I pay taxes, abide by the law, and I'm good to my family. I help people. I believe hands that help are better than hands that pray."