Q: Are there objective criteria that can be used to determine if a person has been possessed by a demon?
A: The new ordinance on exorcism summarises the criteria for the event of possession very well. The clearest for me as a priest is the deep aversion to holy objects such as the cross, the rosary or the sign of the cross. Also an aversion to the word God – when it is spoken, such people get very nervous. Less significant indications are the supernatural capabilities that these people can suddenly develop. They can speak foreign languages that they've never learned. They can levitate; they can float, they can overcome gravity. Sometimes they become inexplicably strong and violent. But it's not that easy to diagnose cases of possession. I usually suggest that people see a neurologist or a psychiatrist before I get involved in their case. If I am advised by these experts that they can't help, then I can begin a spiritual treatment. As a rule, I would say that of ten people who request an exorcism, one is truly possessed.
(As Pharyngula says 'I wonder how often this happens…the priest advises a consult with a neurologist. The neurologist examines the patient; he is floating in mid-air, croaking in Latin: the neurologist calmly says I can't help him.')
Q:Are there reasons for possession?
A: We don't know them. Nor can we say why one person gets cancer and another doesn't.
Q:There is so much evil in the world. Look at all the wars, all the massacres, the tyrants and murderers. Is it not strange that the devil still plays his games with lonely and poor people, taking them over? Couldn't he do better, or rather worse? Isn't he busy enough already?
A: That is truly a mystery.