What is the Jewish view on hypnotism? What is the basis for this?
First off, you must understand that there is a distinction between hypnosis used to help people change destructive behavioral patterns and stage hypnotism which is used in shows. While I am not qualified to give you the particulars of the distinction, be aware that it exists.
That said, hypnosis puts a person into an altered state of conciousness, one in which it is easier to change habits. Rav Moshe Feinstein and other decisors of Jewish Law have said that this is perfectly permissible according to Halacha.
In stage hypnosis the general idea is to put people into a trance-like state and then get them to make fools of themsevles. I have twice been to see such shows and was appalled at what the hypnotist got people to do. It seemed that every one of them was terribly embarrassed by what they had done when they came out of their state, and would certainly have refused to do what they were being asked to do if they were aware. While it is true that they all volunteered for the role it was a terrible display of a lack of human dignity. I don’t see how Jewish Law could permit such a degredation of a fellow human being.