The reactive mind is a concept in the Dianetics and Scientology systems of L. Ron Hubbard, referring to that portion of the human mind that is unconscious and stimulus-response, which Hubbard blamed for most mental and physical ailments. These ailments are regarded by Scientologists as psychosomatic ones:
"What can it do? It can give a man arthritis, bursitis, asthma, allergies, sinusitis, coronary trouble, high blood pressure and so on, down the whole catalog of psychosomatic ills, adding a few more which were never specifically classified as psychosomatic, such as the common cold." - L. Ron Hubbard (Dianetics: The Modern Science of Mental Health, 1999 paperback edition, pg.69)
Despite the lack of scientific basis for his claims, Hubbard maintained, "These are scientific facts. They compare invariably with observed experience. The reactive mind is the entire source of aberration. It can be proved and has been repeatedly proven...." Today, the Church of Scientology still maintains the importance of doing away with this portion of one's mind, and that only Dianetics can achieve this.
"Dianetics gets rid of the reactive mind. It's the only thing that does." - Scientology's website for Bridge Publications
Hubbard's book Dianetics: The Modern Science of Mental Health claimed that the Reactive Mind stores exact impressions (which he called engrams) of past events, which occurred while the person was unconscious or otherwise not completely aware. The common element in these recordings are pain and unconsciousness, which then act to cross associate and cross wire the incidents involved in the mind.
Scientology and Dianetics use a galvanic skin response detector called an E-meter originally designed by Volney Mathison that is basically a Wheatstone bridge designed to help the work of erasing one's own engrams and in the end, supposedly erasing one's own reactive mind altogether, by measuring the changes in resistance experienced by a living organism e. g. a humanoid. This is done through a series of sessions called Auditing.
According to The Sunday Times Biology Oxford Prof. Richard Dawkins states Scientology purports to use scientific tools such as its controversial E-Meter to augment the "gullibiligy" of this already "gullible age".