The number of people unaffiliated with any particular faith has grown more rapidly than any other religious group in recent years. According to a 2007 Pew study, 16 percent of American adults say they don’t belong to any religion, compared to 7 percent who were raised unaffiliated.

The idea for the group came from Darrel Ray, an organizational psychologist and author of “The God Virus: How Religion Infects Our Lives and Culture.” He was raised in a fundamentalist Christian church and attended seminary. But by the time he graduated, he had abandoned the notion of becoming a minister.