score:15
This answer wants to be objective and won't give a plaidoyer pro or contra exorcism.
First some words about the biblical foundation of exorcism.
The idea of an evil power didn't actually play a role in ancient Israel because of the sole and universal power of JHWH – except for two pericopes:
The evil doesn't lay in any demonic power but rather in the weakness of man … until in the postexilic period a belief in demonic power develops (but still they don't have any dualistic principle which assumes an equivalent power beside God).
Biblical passages are:
But nevertheless – the appearance of Satan in the OT is a marginal phenomenon.
Today's image of Satan as a spirit being of divine power is later developed in the non-biblical Jewish literature.
Things are different in the NT – e.g. in the Gospel of Mark: Here we find four exorcistic traditions:
They all say: Jesus had the ability to heal from illness and possession. Similar passages can also be found in the other synoptic Gospels (of Matthew and Luke).
From the three summaries in Mark's Gospel 1:34, 1:39 and 3:11 we know that Jesus did perform exorcism and gave this ability the twelve apostles.
Alright, enough Biblical evidence – what about exorcism today? What do say …
Catholic authors (Dr. Holböck, Pater Rodewyk, J.M. Hartmann, Corrado Balducci, a Bishop of Trier (Franz Rudolf Bornewasser), Pope Benedict XVI.) emphasize that there are cases of real possession that cannot be explained by medical doctors and psychologists.
I quote Joseph Ratzinger:
The evil is not only a psychic component, it's rather an oncoming, independent power that accrues humans. [...] Where HE [God] is, appears he [the devil] as void.
Exorcism is still an official doctrine of the Catholic church.
And what do say …
Luther developed – as part of his Christology – a massive idea of the devil.
But nevertheless an idea of exorcism is practically not present1 in the Protestant Church – there's also no ritual like the Catholic "Rituale Romanum".
There are even some who want to erase an idea of an evil demonic power saying it's superstition, like Rudolf Bultmann:2
The church shall hurry up to exterminate it [the idea of demons]
1: With some exceptions, e.g. Christoph Blumhardt
2: Rudolf Bultmann, ''Kerygma und Mythos'' (1948), p.150
Upvote:5
In Catholicism, it is practised today. It isn't talked much about it, since it is criticised from scientists and medical doctors, which often are Christians themselves, but don't believe in exorcism. To avoid debate, it is a taboo.
And it is dangerous for those, performing the miracle, because if there is serious damage on the client side, it might result in a court case about nonassistance of a person in danger, bodily harm or involuntary manslaughter.
Here are some references:
Here is a 8 years old story from a German newspaper. It talks about a case from Milwaukee, where a protestant [to my surprise] priest accidentally killed a boy, suffering from autism, in kneeing and laying himself on top of the boy while praying. The boy died from suffocation.
Here is a case from the catholic church which shows, that Epilepsy might be for us, what former times thought to be possession. It is interesting, in that a higher, catholic official, Joseph Kardinal Höffner, chairman of the Deutschen Bischofskonferenz in 1978 stated, that daemons are in principal somehing, which his church thinks, are true. They are a sort of angels, build by God, who created them, but some of them turned bad, and then may join humans.
The German version of Wikipedia is more detailed in that respect, so give it a try, if you can read it.
Upvote:6
This answer may not be "objective", but it's a question about exorcism, it's hard to be objective. But I'm a protestant with "exorcism" training (now it's called "Freedom in Christ" to avoid association with pop culture).
Effectiveness:
Exorcisms are often not effective, here's why:
Jesus said if you cast out one demon and the person isn't then filled with the Spirit of God, 7 other demons will return to take it's place, Matthew 12:45. So a good "exorcist" won't exercise someone who isn't going to accept Christ shortly after the exorcism. And, although it's not impossible, demons don't take conversion attempts "lying down" (sometimes they do lie down, but normally kicking and screaming). That said, at the name of Jesus, every knee will bow and success exorcism result in converts.
Support in churches:
In my experience exorcism is supported in some charismatic protestant churches, but they don't often talk about it, because, let's face it, it scares the pants off most believers let alone heathens.