The devil exists and can act upon human beings
It is a doctrine of faith that the devil exists and can act upon human beings. The Catechism of the Church states that: “Behind the disobedient choice of our first parents, there lurks a seductive voice opposed to God, which makes them fall into death out of envy.” Scripture and the Tradition of the Church see in this being a dethroned angel, called Satan or the Devil. The Church teaches that he was previously a good angel created by God but became evil by his own initiative (§391). The Devil is “a sinner from the beginning” (1 John 3:8), the “father of lies” (John 8:44). Jesus calls him the “murderer from the beginning” (John 8:44). “The reason the Son of God appeared was to destroy the works of the devil,” said Saint John (1 John 3:9).
Possession
The Church teaches that the devil can possess a person, take control of their faculties, and for this, it has the Rite of Exorcism to expel him. Jesus performed many exorcisms: “But if it is by the Spirit of God that I cast out demons, then the kingdom of God has come upon you” (Matthew 12:28). It is from Jesus that the Church received the power and the mandate to exorcise.
When the Church publicly and authoritatively demands, in the name of Jesus Christ, that a person or object be protected against the influence of the evil one and withdrawn from his dominion, it is called exorcism.
Liberation
In a simple form, exorcism is practiced during the celebration of Baptism. Since Baptism signifies liberation from sin and its instigator, the Devil, an exorcism is pronounced over the candidate. The candidate is anointed with the oil of catechumens, or the celebrant imposes hands, and the candidate explicitly renounces Satan.
The solemn exorcism, called “great exorcism,” can only be performed by a priest with the permission of the Bishop. It is necessary to proceed with prudence, strictly observing the rules established by the Church. It is important, therefore, to ensure, before performing the exorcism, whether it is a presence of the evil one or a mental illness.
Instruction
The Vatican’s Congregation for the Doctrine of the Faith, on September 24, 1985, issued an Instruction on Exorcism, which recalls the following:
Canon 1172 of the Code of Canon Law declares that no one is allowed to perform exorcism on possessed persons unless the Ordinary of the place has granted specific and explicit permission for it (1st). It also determines that this permission can only be granted by the Ordinary of the place to a priest endowed with piety, wisdom, prudence, and integrity of life.
Formula
It is not lawful for Christian faithful to use the exorcism formula against Satan and apostate angels contained in the Rite published by order of Pope Leo XIII. It is even less lawful for them to apply the entire text of this exorcism.
Bishops are requested to ensure that, even in cases that may reveal some influence of the devil, excluding genuine demonic possession, individuals not duly authorized do not lead meetings where prayers are made to obtain the expulsion of the demon, prayers that directly address demons or express a desire to know their identity.