Exorcisms

The following comes primarily from Fr. Gabriele Amorth's An Exorcist: More Stories^[1] though a few Catholic Encyclopedia articles might technically be the origin of some fact or two. It comes as a result of needing to research the topic for the summer education at St. Veronica's, where the teens are to watch "The Exorcism of Emily Rose" this evening.

1. Ghosts and/or poltergeists exit: FALSE. These are believed to be the "spirit" or soul of a dead person who has somehow not gone on to heaven, hell, or purgatory. This does not in fact ever happen. All souls go to one of these three destinations.
2. Demons or devils exist: TRUE. Demons or devils are fallen angels, Satan and those who followed him in rebellion against God. The Catholic Encyclopedia writes

   According to Catholic belief demons or fallen angels retain their natural power, as intelligent beings, of acting on the material universe, and using material objects and directing material forces for their own wicked ends; and this power, which is in itself limited, and is subject, of course, to the control of Divine providence, is believed to have been allowed a wider scope for its activity in the consequence of the sin of mankind. Hence places and things as well as persons are naturally liable to diabolical infestation, within limits permitted by God

3. Demons can only possess the sinful: FALSE. The bible lists at least one instance of a child having been possessed from birth, thus we know that no action on the part of the person is necessary. Conversely, the need for exorcism persists through the Acts of the Apostles, and in the writings of the early Church. Exorcists still act under the direction of the bishops today, and those they aid include both Catholics and non-Catholics, both those with strong prayer lives and those with- out.
4. Possession is really just mental disease: FALSE. While there have, historically, been mistakes in diagnosis, times when mental disease was wrongly taken to be the result of demonic influence or possession, it is not the case that demonic possession is always the result of mental disease. Just so, there have times when people have been wrongly convicted of murder, we do not dis- regard the possibility of murder. Further, even in the Bible, we see a distinction made between possession and mental disease. For example, Matthew 4:24 reads

   His fame spread to all of Syria, and they brought to him all who were sick with various diseases and racked with pain, those who were possessed, lunatics, and paralytics, and he cured them.

   Here we see a distinction made between the insane, the paralyzed, and the possessed. Yet possession, in other parts of the Gospels, is linked with symptoms that could be caused by mental illness or paralysis. If possession were not a separate phenomena, Matthew would have had no need in 4:24 to make the distinction. This is not to say that there has never been a misdiagnosis in either direction. There has, but that does not negate the reality of both.
5. Exorcisms always work: FALSE. Matthew chapter 17 contains a story of a boy whom the Disciples could not exercise. Jesus, after driving the demon out, tells the disciples that their failure resulted from a lack of faith. Else where, Jesus says that some demons can only be exorcised by prayer and fasting. For this reason, the bishops should exercise care in choosing exorcists, to pick priests with a strong faith, and who live holy lives. Even then, exorcists have related that it sometimes takes years for complete healing.

Some further notes gleaned:

Ordinary activity is essentially temptation, to which we are all subject, and is not covered by him.

He breaks extraordinary activity down into 6 categories: 1)External Pain caused either directly or indirectly (as by the demon causing an object to fall would be a source of indirect pain) 2)possession continuing presence of a demon in the person. typically alternating between periods of rest and activity (by the demon) and involves the suspension of "mental, intellectual, affective and volatile functions." It can include the knowledge of languages the person would not normally know, superhuman strength, superhuman knowledge, and/or the ability to read thoughts. A strong temptation to suicide is often present as well. 3)oppression random discomfort, often appearing very similar to severe depression, with inexplicable rages, and a strong tendency to isolation and a strong temptation to suicide. 4)obsession almost a split personality. the will remains free, but thoughts, often very illogical ones, persist in the mind, and cannot be dispelled by the person. there is often a strong temptation to suicide. 5)infestation demonic activity directed at places (houses, offices, stores, fields), objects (cars, pillows, mattresses, dolls), or animals. 6)subjugation a voluntary pact with a demon, either implicit or explicit. Otherwise similar to one of the first 4.

he lists 4 categories of ways in which one of these comes about: 1)Pure divine permission the person has done nothing, is in fact growing in virtue. God grants permission much as happens with Job in the bible. 2)subjection to a curse one person requests a demon to harm another. 3)grave hardening in sin such as Judas Iscariot, the person who has abandoned themselves to sin of any sort is at greater risk of demonic harm. He also lists abortion here. 4)proximity to evil associating with satanic cults, with magicians or fortune tellers, dabbling with magic or witch doctors. He also includes the effects of pornography, some rock (and especially rap) music, some horror movies, and other, similar parts of popular culture.