Founded in 1953 by the science-fiction writer L. Ron Hubbard, Scientology is a philosophy and set of religious beliefs centered on the principles of self-understanding and self-improvement.
The fundamental beliefs of Scientology were first outlined by Hubbard in his book "Dianetics: The Modern Science of Mental Health" (1950). According to this work, the main goal of Scientology is to do away with unhappiness, which Scientologists believe is caused by negative memories of prior experiences. These memories, or "engrams" as they're known within the religion, are believed to influence a person's mind in such a way that he or she repeats certain destructive behaviors.
Scientologists rid their mind of engrams by participating in therapy sessions, called "audits." They also regularly undergo counseling and are introduced to educational materials within their religion. The goal of these techniques is to become what's known as a "clear," or someone free of engrams.
Scientologists also believe that human beings possess a spiritual essence, called a "thetan." Once a Scientologist becomes clear, he or she strives to attain the many levels of understanding associated with "Operating Thetans" (OTs), who are believed to be able to control the world around them with their minds.
Like many new religious movements of the 20th century, Scientology has been widely criticized by other religious organizations, as well as the media. One of the main causes of such criticism is the fact that Scientologists must pay to participate in the "auditing" sessions and other techniques used to attain a higher level of understanding within their faith.
Other sources of mainstream conflict include Scientology's stance on mental health care (members are not permitted to use any form of psychiatric drug), the validity of the Church of Scientology's tax-exempt status as a religious organization, as well as its zero-tolerance policies regarding any form of dissent or opposition to Hubbard's teachings.
Despite numerous controversies surrounding the religion, Scientology has been adopted by a number of well-known figures, including Tom Cruise, Kirstie Alley and John Travolta. A 2001 survey by the City University of New York found that there were approximately 55,000 practicing Scientologists in the United States. Worldwide membership is believed to range from 100,000 to 200,000 active members.