Hypnosis is an old modality. It is looked upon as both a special state or a special process. I prefer to view hypnosis as a process of transmitting ideas which requires a special state of receptivity, like for example a state of focused attention, daydreaming or simply trance. This process results in a behavioral change in a subject.
Clinical hypnosis is not faith healing. You don't have to believe in it in order for it to work. You don't have to believe in any deity or supernatural ability of a hypnotist either. There is a simple formula to hypnosis: a state of receptivity followed by suggestions. The state of mental and physical relaxation, required for programming of the mind in clinical hypnosis - can be naturally induced with a variety of hypnotic inductions.
Finally, anyone with normal intelligence (or above) who is willing to follow the instructions of a hypnotist can be hypnotized.