The thetan is described in Scientology as having no mass, no wavelength, no energy and no time or location in space except by consideration or postulate. The spirit, then, is not a thing. It is the creator of things.
The usual residence of the thetan is in the skull or near the body. A thetan can be in one of four conditions. The first would be entirely separate from a body or bodies, or even from this universe. The second would be near a body and knowingly controlling the body. The third would be in the body (the skull) and the fourth would be an inverted condition whereby he is compulsively away from the body and cannot approach it. There are degrees 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, since it has been discovered that he is happier and more capable when so situated.
The mind is a communication and control system between the thetan and his environment. The mind is a network of communications and pictures, energies and masses, which are brought into being by the activities of the thetan versus the physical universe or other thetans. A thetan establishes various systems of control so that he can continue to operate a body and through the body operate things in the physical universe, as well as other bodies. The most obvious portion of the mind is recognizable by anyone not in serious condition. This is the mental image picture. In Scientology we call this mental image picture a facsimile when it is a photograph of the physical universe sometime in the past. We call this mental image picture a mock-up when it is created by the thetan or for the thetan and does not consist of a photograph of the physical universe. We call a mental image picture a hallucination or, more properly, an automaticity when it is created by another and seen by self.
Various phenomena connect themselves with this entity called the mind. Some people closing their eyes see only blackness, some people see pictures. Some people see pictures made by body reactions. Some people see only black screens. Others see golden lines. Others see spaces, but the keynote of the entirety of the system called the mind is postulate and perception. Easily ten thousand new, separate mental phenomena, not hitherto seen by earlier observers, have been classified in Scientology and Dianetics.
The thetan receives, by the communication system called the mind, various impressions, including direct views of the physical universe. In addition to this he receives impressions from past activities and, most important, he himself, being close to a total knowingness, conceives things about the past and future which are independent of immediately present stimuli. The mind is not in its entirety a stimulus-response mechanism as old Marxist psychology, as once taught in universities, would have one believe. The mind has three main divisions. The first of these could be called the analytical mind, the second the reactive mind and the third the somatic mind.