Bridge: the sequence of activities done to gradually achieve the states of existence called Clear and OT. It is also called the Classification, Gradation and Awareness Chart. The Bridge shows the route to Clear and the OT states beyond.
Classification means here that there are certain actions required to be done or conditions to be attained before an individual is classified for a particular training level and allowed to progress up. Gradation means a gradual grade up, just as there are grades to a road or there are grades to steps. Awareness refers to one’s own awareness, which improves as one progresses up. On the right side of the chart there are various steps called the States of Release. The left-hand side of the chart describes the very important steps of training on which one gains the knowledge and abilities necessary to deliver the Grades of Release to another. It is a guide for the individual from the point where he first becomes dimly aware of a Scientologist or Scientology and shows him how and where he should move up in order to make it. Scientology contains the entire map for getting the individual through all the various points on this gradation scale and for getting him across the Bridge to higher states of existence. See also Bridge, The; Grades of Release.
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Clear: the name of a state achieved through auditing or an individual who has achieved this state. A Clear is a being who no longer is affected by past traumas and grief. A Clear is rational in that he forms the best possible solutions he can on the data he has and from his viewpoint.
Operating Thetan (OT): it is a state of beingness. It is a being “at cause over matter, energy, space, time, form and life.” Operating comes from “able to operate without dependency on things,” and Thetan is the Greek letter Theta (), which the Greeks used to represent thought or perhaps spirit, to which an n is added to make a noun in the modern style used to create words in engineering. Abbreviation: OT
(Source: What is Scientology? Book online)