The Church of Scientology maintains a wide variety of beliefs and practices. The core belief holds that a human is an immortal, spiritual being (thetan) that is resident in a physical body. The thetan has had innumerable past lives, some of which, preceding the thetan's arrival on Earth, were lived in extraterrestrial cultures. Based on case studies at advanced levels, it is predicted that any Scientologist undergoing auditing will eventually come across and recount a common series of events.