Exorcism
In Catholic practice the person performing the exorcism, known as an exorcist, is an ordained priest. The exorcist recites prayers according to the rubrics of the rite, and may make use of religious materials such as icons and sacramentals. The exorcist invokes God—specifically the Name of Jesus—as well as members of the Church Triumphant and the Archangel Michael to intervene with the exorcism. According to Catholic understanding, several weekly exorcisms over many years are sometimes required to expel a deeply entrenched demon.
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.