The phenomenon of artificially induced sleep, which renders the victim abnormally open to suggestion. The subject of hypnosis tends to be dominated by the ideas and suggestions of the hypnotist while under the induced spell and later on. According to Catholic principles, hypnotism is not wrong in itself, so that its use under certain circumstances is permissible. But since it deprives the subject of the full use of reason and free will, a justifying cause is necessary for allowing it to be practiced. Moreover, because hypnotism puts the subject's will in the power of the hypnotist, certain precautions are necessary to safeguard the subject's virtue, and to protect him or her and others against the danger of being guilty of any injurious actions. For grave reasons, e.g., to cure a drunkard or one with a suicide complex, it is licit to exercise hypnotism, given the precaution that it is done in the presence of a trustworthy witness by a competent and upright hypnotist. The consent, at least presumed, of the subject must also be had. Several documents of the Holy See set down the norms to be followed in the use of hypnotism (The Holy Office, August 4, 1956; July 26, 1899).