“The usual residence of the thetan is in the skull or near the body. A thetan can be in one of four conditions:
“1. The first would be entirely separate from a body or bodies, or even from this universe.
“2. The second would be near a body and knowingly controlling the body.
“3. The third would be in the body (the skull).
“4. And the fourth would be an inverted condition, whereby he is compulsively away from the body and cannot approach it.
“There are degrees (subdivisions) of each one of these four states. The most optimum of these conditions, from the standpoint of Man, is the second.
“A thetan is subject to deterioration. This is at first difficult to understand, since the entirety of his activity consists of considering or postulating. He uses, through his postulates. various methods of controlling a body. That he does deteriorate is manifest. But that he can at any moment return to an entirety of his ability is also factual. In that he associates beingness with mass and action, he does not consider himself as having an individual identity or name unless he is connected with one or more of the games of life.
“The processes of Scientology can establish this for the individual with greater or lesser rapidity. And one of the many goals of processing in Scientology is to “exteriorize” the individual and place him in the second condition above (near a body and knowingly controlling the body), since it has been discovered that he is happier and more capable when so situated.”
LRH Book, Fundamentals of Thought