"Cult" is not a neutral word in American culture. In common usage, it often refers to a group outside the mainstream—a group with abnormal, crazy, perhaps even sinister ideas or practices. Cults that have gained the most public attention tend to reinforce this image.

Social scientists say that to be labeled a "cult" an organization must meet the criteria of size, doctrine, and time. A cult tends to be small in membership, anywhere from a handful to a few hundred. Cults also tend to have one or more differences in doctrine from established religions—a cult may believe in a different god or may have forms of worship not shared by other churches. Finally, a cult is usually new on the scene, which gives it the status of "outsider."

Christianity was considered a cult by the Romans throughout the first century C.E., until it grew in...