Exorcism in Christianity
Exorcism in Christianity is the practice of casting out demons from a person they are believed to have possessed. The person performing the exorcism, known as an exorcist, is often a member of the Christian Church, or an individual thought to be graced with special powers or skills. The exorcist may use prayers and religious material, such as set formulas, gestures, symbols, icons, amulets, etc. The exorcist often invokes God, Jesus and/or several different angels and archangels to intervene with the exorcism. A survey of Christian exorcists found that most exorcists believe that any mature Christian can perform an exorcism, not just members of clergy. Christian exorcists most commonly believe the authority given to them by the Father, Son, and Holy Spirit (the Trinity) is the source of their ability to cast out demons.
The Exorcist (novel)
Recent investigative research by freelance journalist Mark Opsasnick indicates that Blatty's novel was based on an actual 1949 exorcism of a young boy from Cottage City, Maryland, whom Opsasnick refers to using the pseudonyms Robbie Mannheim and Roland Doe. The boy was sent to his relative's home on Roanoke Drive in St. Louis where most of the exorcism took place.