But while their mysterious powers have been glamorised in popular literature and horror movies, one ancient and massively influential institution, the Catholic Church, has never doubted them.
Exorcists have always been recognised by the Catholic Church and an updated rite has been put in place, with regular courses for priests, in Rome.
And since the last papacy, under Benedict XVI, the rest of the world has noticed the increased interest of the Catholic hierarchy in the ancient ritual of exorcism.
During his term, Benedict was reported to have frequently welcomed exorcists from across the globe at special audiences in the Vatican.
But his successor, Pope Francis, raised their profile even further last May, when images were beamed across the world appearing to show him carrying out an exorcism on a young man with a disability, in St Peter’s Square.
As the Pontiff laid both hands on the man’s forehead, the man visibly moved in his wheelchair and his body appeared energised and animated.
Some observers said it was merely the excited reaction of a devout young Catholic face-to-face with his spiritual father.
But for many people it was evidence that Pope Francis had performed an exorcism — the rite that can be traced back to the time Jesus Christ fought off temptations from the Devil in the desert.
Here in Ireland, the Catholic Church is no less supportive of the secretive ritual and its priestly practitioners.
A fascinating documentary, which aired on TG4 last Sunday, revealed that a number of priests here have been trained to carry out exorcisms in response to a growing demand from parishioners.
At least three clergymen have been taught how to perform exorcisms on people who believe they have been possessed by demonic spirits.
In the programme, Dibirt Deamhain, Fr Fiontán Ó Mónacháin&, secretary to the Archbishop of Tuam, gave a fascinating insight into the little known world of exorcists.
Fr Ó Mónacháin said: “When someone approaches us with a request for an exorcism, they usually approach their parish priest first.
“That priest would have a good idea if it’s a psychiatric or a spiritual issue.
“If it’s a spiritual problem, the priest would usually say prayers or celebrate Mass in the house, or give a special blessing using holy water.
“If that doesn’t work and if they are still suffering, a formal exorcism may be necessary. And if that’s the case, there are priests in the country who are trained in that field.
“There aren’t many. I know of a Jesuit priest in Galway, and there is another priest in the Killaloe diocese, and a Franciscan priest from Carlow.
“We refer people to those priests and the bishop gives them permission to carry out the exorcism.”
Fr Ó Mónacháin also said that demand for exorcisms from priests had increased over the past decade.
He said: “Perhaps it has become more popular again, as there has been more demand for it in the last ten years. This is evidence from the requests priests are receiving.”
As Ireland becomes increasingly secularised, it’s perhaps no surprise that there has been a surge in the number of people seeking exorcisms from spiritual healers who are not part of the clergy.
Members of the New Charismatic Movement, and a former Irish soldier-turned-Shaman, told the programme’s makers of their sometimes terrifying experiences with possessed people.
The documentary also recounted the chilling story of two Irish seminarians, who deemed themselves possessed by demons and threw themselves from the same window, in St Patrick’s, Maynooth, 19 years apart.
Trainee priest Sean O’Grady fell to his death from the third-floor window of Rhetoric House in 1941, but the second seminarian, Thomas McGinn, survived long enough to say he was tormented by demons.
An exorcism was performed in the room, after which the wall between the room and corridor was knocked down.
The window was removed and a statue of St Joseph was quickly erected in its place.
However, for every believer there are many more people for whom exorcisms are a charade of bizarre paranormal activity and flying crucifixes.
And as the documentary observed, exorcists’ biggest detractors are scientists and doctors.
Dublin psychiatrist, Dr Siobhan Barry, said in the programme: “There was a time when it was believed that people who suffered from epilepsy were possessed by spirits.
“When I think of the pros and cons of exorcism, I think of the biggest con of all.”
EXORCISM is the practice of evicting demons or other spiritual entities from a person, or an area, they are believed to have possessed.
Depending on the spiritual beliefs of the exorcist, this can be done by causing the entity to swear an oath, performing an elaborate ritual, or simply by commanding it to depart in the name of a higher power.
The ancient belief system is part of the belief system of many cultures and religions.
Requested and performed exorcisms had begun to decline in the Western world by the 18th century due to advancements in medicine.
But there was a sharp rise in demand for the services of exorcists in the latter half of the 20th century. Spurred on by increased media attention, the 60s and 70s saw a 50% rise in demand worldwide for exorcisms.
HOLLYWOOD’S love affair with exorcists kicked off in the 60s, spurning hundreds of low-budget horror flicks which reached its peak in the following decade.
The all-time classic is William Friedkin’s The Exorcist, a controversial 1973 spine-chiller that spooked an entire generation of movie-goers.
It’s graphic nature was deemed inappropriate for Irish audiences, and cinema-goers had to wait until 1998 until they got to see the uncut original for the first time.
Other chilling exorcism movies include The Exorcism of Emily Rose, which was based on the tragic real-life story of Anneliese Michel,a German girl who died in an exorcism.