Thetan
In Scientology, the concept of the thetan (/ˈθeɪtən/) is similar to the concept of self, or the spirit or soul as found in several belief systems. This similarity is not total, though. The term is derived from the Greek letter Θ, theta, which in Scientology beliefs 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.
Thetan-1