One of the masters of modern hypnosis, Milton Erickson identified hypnosis as a "state of intensified attention and receptiveness and an increased responsiveness to an idea or to a set of ideas." (Erickson, 1958)
Hypnosis has also been described as a "state of selective hyper-suggestibility.." (Weitzenhoffer, A. 1957)
Therefore, hypnosis is a particular state of consciousness in which a person responds to his/her own suggestions or those from others. A suggestion is commonly defined as an idea offered to oneself or another for uncritical acceptance.
The premise of this technique is that the suggestions will bypass the patient's conscious critical judgment and become a part of his/her subconscious mind. This a the part of the mind believed to motivate one's thoughts, feelings, and behavior.
In the case of substance abuse, for example, the patient may associate the use of a substance with pleasurable, carefree, confident state. There also may be such ideas as "I can not go without it", If I do not have it I will die, Without it life is boring..." The therapist gives suggestions to the patient about the negative effects of the substance on the patient's life and the positive consequences of giving it up. Through the use of suggestions the therapist also might create a conditioned response between a particular word and a feeling of a commitment to becoming abstinent. The suggestion may be: "Any time you feel the desire to... take a deep breath and say to yourself "freedom." A patient is asked to do this in the therapists office while he/she is relaxed and committed to becoming free, and then again whenever in challenging life situations.
The utilization of such techniques comes from the belief that once the suggestions reach the patient's subconscious mind they will extinguish the old conditioning (in the presented example: substance-pleasure, substance-carefree life), and create a new conditioning (in the presented example: abstinence-freedom, abstinence-self-respect...).