The current level of curiosity about exorcisms in Catholic practice has come about because of a widespread preoccupation with Satanism and various occult practices.
Satanism and the occult have always been around. Christian faith teaches that Jesus Christ definitively destroyed the power of Satan. This happened at the Resurrection when darkness and death were defeated. The final victory will be Christ returns at the Last Judgement.
Exorcisms were performed by Jesus Christ, who gave authority and power to his apostles to protect people and objects from the residual power of the Evil One, and to deal with any demonic infestations they encountered.
The Church recognises various forms of exorcism. Minor exorcism ordinarily takes place in many of the Church’s rites and sacraments, using the sign of the cross, and in the blessing of people and material things such as holy water.
Priests in their ordinary parish work can encounter a variety of paranormal phenomena troubling people and places, especially places and people given to the practice of esoteric activity.
A necessary distinction is made between psychological illness affecting a person, whose treatment is the proper concern of medical science, and true manifestations of the presence of the Evil One.
People can have obsessions and compulsions in various areas of behaviour which may be addressed through psychological counselling and treatment. However, there may also be the possibility of evil spirits associated with the condition, bringing about a real spiritual oppression.
The assistance which a priest can give in such situations, and the prayers which he employs, whether called by the term or not, are a form of minor exorcism. They can bring clearly experienced relief from spiritual darkness, and forms of demonic oppression.
Major exorcism, however, may be required in rarer cases where it is established by appropriate investigation that the victim’s claim to be tormented by a demon is really true. Major exorcism is strictly regulated by the Church and can only be deputed by the bishop to a priest of exemplary virtue, knowledge, prudence and integrity of life.
These cases, when they rarely occur, are treated with great discretion and the priest authorised by the local bishop need not be from his own diocese but rather a priest specialising more widely in this work of the Church. Direct confrontation with the Evil One is a serious matter requiring great spiritual strength and precise method of attack. The actual rites of major exorcism however are not secret, although they exist only in Latin and unofficial translation.