Demon
The contemporary Roman Catholic Church unequivocally teaches that angels and demons are real beings rather than just symbolic devices. The Catholic Church has a cadre of officially sanctioned exorcists which perform many exorcisms each year. The exorcists of the Catholic Church teach that demons attack humans continually but that afflicted persons can be effectively healed and protected either by the formal rite of exorcism, authorized to be performed only by bishops and those they designate, or by prayers of deliverance, which any Christian can offer for themselves or others.
Unclean spirit
Exorcism is the most thoroughly attested Jewish magical practice of the Second Temple period. The exorcistic technique of fumigation by incense depends on the aerial conception of the unclean spirit: the occupation of air by odor or smoke (i.e., airborne particulate matter) was supposed to drive off or displace an unclean spirit. Since either body or soul could be unclean, it can be difficult to distinguish exorcism from traditional magico-medical practice in which a personified illness is adjured to depart from the patient's body (for instance, "Flee, Fever!") by means of a charm, spoken or inscribed on an amulet or other ritual object. In some rabbinic literature, demons are viewed as inflicting evil on humans in part through illness and disease, though Mishnah and Tannaitic scholars in Palestine did not view demons as the cause of illness.