Here are a couple of Frequently Asked Questions about the mind as relayed in the book DIANETICS.
What is the Mind?
The mind is basically a communication and control system between the person and his environment. It is composed of mental image pictures, which are recordings of past experiences. The individual uses his mind to pose and solve problems related to survival and to direct his efforts according to these solutions.
What is the Reactive Mind?
The reactive mind is the portion of a person's mind which works on a totally stimulus-response basis, which is not under his volitional (willing) control, and which exerts force and the power of command over his awareness, purposes, thoughts, body and actions.