In Scientology, the concept of thetan (// THAY-tən) is similar to the concept of spirit or soul found in other belief systems. The term is derived from the Greek letter theta, which in Scientology represents "the source of life, or life itself." In Scientology it is believed that it is the thetan, not the Central Nervous System, which commands the body through communication points. This conception of the spirit in Scientology is represented by the Greek letter Θ, theta.
Thetans have been described in the Church of Scientology in a number of ways.
- A "thetan is an immortal spiritual being; the human soul."
- "The being who is the individual and who handles and lives in the body."
- "A thetan is not a thing, a thetan is the creator of things."
- A thetan is "the person himself — not his body or his name, the physical universe, his mind, or anything else; that which is aware of being aware; the identity which is the individual. The thetan is most familiar to one and all as you."
Thetan in Scientology doctrine 
The term and concept were defined by Scientology founder L. Ron Hubbard, who adopted the Greek letter theta (Θ) to represent "the source of life and life itself". Hubbard first introduced his ideas of "theta-beings" in a lecture series of March 1952. He attributed the coining of the word to his wife Mary Sue. As an essential point of Scientology doctrine, a person's identity and self-awareness come entirely from a "thetan". It is redundant to refer to "a person's thetan," because the person does not exist independently.
Hubbard once defined a thetan as: "... having no mass, no wave-length, no energy, no measurable qualities and no time or location in space except by consideration or postulate. The spirit is not a thing. It is the creator of things." In a lecture series later published as a book ("The Phoenix Lectures"), he jokingly pointed to a study that implied that a "thetan" manifests a small but measurable amount of mass:
- "From some experiments conducted about fifteen or twenty years ago — a thetan weighed about 1.5 ounces [45 grams]! Who made these experiments? Well, a doctor made these experiments. He weighed people before and after death, retaining any mass. He weighed the person, bed and all, and he found that the weight dropped at the moment of death about 1.5 ounces [45 grams] and some of them 2 ounces [60 grams]. (Those were super thetans!)"
Although Hubbard did not name the doctor concerned, there was indeed such an attempt, by Dr. Duncan MacDougall, to measure the weight of dying patients to determine the weight of the soul, although MacDougall's experiments took place about fifty years before Hubbard's lectures, not fifteen or twenty, and are generally not regarded as having any scientific validity.
According to Hubbard's son Ronald DeWolf (born L. Ron Hubbard, Jr.), his father stated that thetans are immortal and perpetual, having willed themselves into existence at some point several trillion years ago. After they originated, thetans generated "points to view" or "dimension points", causing space to come into existence. They agreed that other thetans' dimension points existed, thus bringing into existence the entire universe. All matter, energy, space, and time exists solely because thetans agree that it exists.
In the primordial past, according to Scientologist teachings, thetans brought the material universe into being largely for their own pleasure.." The universe is thought to have no independent reality, but to derive its apparent reality from the fact that most thetans agree it exists. Scientologists believe that thetans fell from grace when they began to identify with their creation, rather than their original state of spiritual purity. Eventually, they lost their memory of their true nature, along with the associated spiritual and creative powers. As a result, thetans came to think of themselves as nothing but embodied beings.
Thetans are believed to be reborn time and time again in new bodies through a process called "assumption" which is analogous to reincarnation. Dell deChant and Danny Jorgensen liken Scientology to Hinduism, in that both ascribe a causal relationship between the experiences of earlier incarnations and one's present life. With each rebirth, the effects of the "MEST" universe (MEST here stands for matter, energy, space, and time) on the thetan are believed to become stronger.
Jon Atack, whose book A Piece of Blue Sky details how he reached Operating Thetan level V before leaving Scientology, describes Hubbard's doctrines about thetans: "Thetans are all-knowing beings, and became bored because there were no surprises. Hubbard asserted that the single most important desire in all beings is to have a "game". To have a "game" it was necessary to "not know" certain things, so certain perceptions were negated ("not-is-ed")." Since thetans knew everything, this required them to abandon or suppress perceptions and knowledge. Over time, the loss of perception accumulated and certain thetans began to cause harm to others. MEST (physical) beings also sought to "trap" thetans in order to control them. Thetans came to learn contrition, punishing themselves for their own "harmful" acts.
According to Hubbard, an essential part of the thetans' game was the "conquest" of matter, energy, space, and time by the life force, theta. This has produced multiple universes which have ended and begun in succession, each new one being more solid and entrapping than the last. The thetans have by now become so enmeshed in the physical universe that many have identified themselves totally with it, forgetting their quadrillions of years of existence and their original godly powers.
According to Scientology, thetan powers are said to remain potent and restorable. One of the Church of Scientology's stated goals is "the rehabilitation of the human spirit", by which it means the restoration of the thetan's original abilities. Hubbard claims that thetans are able to change reality through "postulates" — decisions made by the individual about the nature of the reality around them. Some thetans are said to have (mis)used this ability to "implant" others with hypnotic suggestions, forcing other thetans to "cluster" around bodies (hence body thetans). This sort of directed control is referred to as "other-determinism". Scientology seeks to undo it and return the thetan to "self-determinism", where he can control himself and his environment. The eventual goal is to achieve "pan-determinism", where he acts for the good of all.
Thetans and death 
Non-Scientologists Joel Sappell and Robert Welkos described in a 1990 article in the LA Times how Scientologists believe that when a person dies — or, in Scientology terms, when a thetan abandons its physical body — they go to a "landing station" on the planet Venus, where the thetan is re-implanted and told lies about its past life and its next life. The Venusians take the thetan, "capsule" it, and send it back to Earth to be thrown into the ocean off the coast of California. They quote Hubbard as saying, "If you can get out of that, and through that, and wander around through the cities and find some girl who looks like she is going to get married or have a baby or something like that, you're all set. And if you can find the maternity ward to a hospital or something, you're OK. And you just eventually just pick up a baby."
Operating Thetan 
According to Scientology doctrine, a thetan exists whether operating a human body or not. Scientology advertises itself as being able to "rehabilitate" the thetan of a practitioner to a state where the individual can operate with or without a "flesh body". The term "operating thetan" would then apply as it does when an individual is operating a body. The Operating Thetan (OT) levels are the upper level courses in Scientology.
The Church of Scientology states as a point of doctrine that an individual exists with or without a body.
Cleared Theta Clear 
Even beyond the Operating Thetan levels comes the "Cleared Theta Clear", a godlike state which Hubbard describes this way:
"A thetan who is completely rehabilitated and can do everything a thetan should do, such as move MEST and control others from a distance, or create his own universe; a person who is able to create his own universe or, living in the MEST universe is able to create illusions perceivable by others at will, to handle MEST universe objects without mechanical means and to have and feel no need of bodies or even the MEST universe to keep himself and his friends interested in existence".
Body thetan 
A body thetan is a disincarnate thetan who is "stuck" in, on or near a human body, and all human bodies are said to be infested by these disembodied thetans, or clusters of them. This information is not revealed until a Scientologist reaches Section III of the Operating Thetan levels (commonly referred to as "OT III"). Body thetans were said by Hubbard to be a result of a prehistoric "Incident" involving Xenu.
- Hubbard (June 1975). Dianetics and Scientology Technical Dictionary. Bridge Publications. p. 432. ISBN 0-88404-037-2.
- "Nerve Assist - Assists for Illnesses and Injuries, How can Scientology help me". Scientologyhandbook.org. 2011-02-15. Retrieved 2011-11-22.
- Official Glossary of Scientology & Dianetics Terms[dead link]
- Science of Survival, L. Ron Hubbard pg.3 pub. Publications Organization ISBN 0-88404-001-1
- Scientology: Milestone One, L. Ron Hubbard pub. Golden Era Productions. Audio lectures with transcripts
- Hubbard, The Auditor 21, p.1
- What is Scientology
- Creed of the Church of Scientology
- Hubbard, The Phoenix Lectures, p. 147. Bridge Publications, 1982 ISBN 0-88404-006-2.
- Mikkelson, Barbara; Mikkelson, David P. (2003-10-27). "Soul Man". Snopes. Retrieved 2007-02-17. "MacDougall's ... methodology ... was suspect, [his] sample size far too small, and [his] ability to measure changes in weight imprecise. For this reason, credence should not be given to the idea his experiments proved something, let alone that they measured the weight of the soul ... His postulations on this topic are a curiousity, but nothing more."
- Billion in Long Scale
- PBS Late Night interview with Ron DeWolf
- Hopkins, Joseph M., Is L. Ron Hubbard Dead?, Christianity Today, 18 February 1983, p 31
- Neusner, Jacob (2003). World Religions in America. Westminster John Knox Press. pp. 221–236. ISBN 0-664-22475-X.
- Chryssides, George D. (1999). Exploring New Religions. Continuum International Publishing Group. p. 283. ISBN 0-8264-5959-5.
- Melton 2000, p. 32
- Atack, Jon (1990). A Piece of Blue Sky. New York, NY: Carol Publishing Group. ISBN 0-8184-0499-X.
- Thousands of billions in Long Scale
- Sappell, Joel; Welkos, Robert W. (1990-06-24). "Defining the Theology". Los Angeles Times. p. A36:1. Retrieved 2007-04-16. Additional convenience link at .
- Cempa, Joe; "Petrolia's New Neighbors", North Coast Journal, June 1991.
- L. Ron Hubbard's Congress Lectures: Glossary, "OT", Bridge Publications Inc.
- Church of Scientology, Scientology Beliefs, accessed 03/28/06
- Hubbard, Scientology 8-8008, pg 114 (1st ed), pg. 151 (1990 ed.)