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.
Exorcism in Christianity
Solemn exorcisms, according to the Canon law of the church, can be exercised only by an ordained priest (or higher prelate), with the express permission of the local bishop, and only after a careful medical examination to exclude the possibility of mental illness, and in the ritual people cannot in any circumstance be harmed. The "Catholic Encyclopedia" (1908) enjoined: "Superstition ought not to be confounded with religion, however much their history may be interwoven, nor magic, however white it may be, with a legitimate religious rite." Things listed in the Roman Ritual as being indicators of possible demonic possession include: speaking foreign or ancient languages of which the possessed has no prior knowledge; supernatural abilities and strength; knowledge of hidden or remote things which the possessed has no way of knowing; an aversion to anything holy; and profuse blasphemy and/or sacrilege.