Exorcism and the entanglement of the rational and religious world-view

People affected by paranormal activity sometimes contact the clergy to perform a blessing or an exorcism. These practices attract criticism on the grounds that they are not based on evidence but are led by assumptions: that the source of the activity is supernatural rather than natural; or that prayers and blessings can have any effect.

Looking into the topic a little more deeply, I’ve been surprised to discover just how much science owes to exorcism; and also how the exorcist’s world-view can appear similar to that of the rationalist.

In 1784, Benjamin Franklin and Antoine Lavoisier undertook what are now recognised as the first placebo-controlled experiments. Franz Anton Mesmer had claimed the discovery of ‘animal magnetism’, which he described as a ‘fluid’ that could be directed at his patients to produce physical, healing effects. Franklin and Lavoisier debunked these claims by presenting patients with water the patient had been told was ‘magnetised’ – when it wasn’t – whilst also surreptitiously applying water to them that had been magnetised. Guess what? The untreated water was observed to cause an effect, whereas the treated water produced no reaction whatsoever. And thus, the placebo-controlled experiment was born: the validity of a treatment was being determined by leaving the patient in the dark as to whether he or she were actually receiving the treatment, or merely being told that they were.

Franklin Routs The Mesmerists

Franklin Routs The Mesmerists (Le magnétisme devoilé. Bibliothèque Nationale de France).

However, Franklin and Lavoisier did not claim to have invented this procedure. They were imitating the well-known techniques of exorcists from almost 200 years before. In 1598 Henri IV had formalised a peace with the Huguenots, but the following year, when a woman became so badly possessed by demons she was subject to almost daily exorcisms, and she began declaring that all Huguenots belonged to Beelzebub, Henri dispatched a commission to remedy the situation. Its members gave the woman ordinary water from a vessel presented as holy water, and she contorted in pain; when they read her Latin verses from the Aeneid, after telling her they were from the Bible, she squirmed in agony, etc., etc. And so the problem was neutralised.

Although they wouldn’t have understood it in these terms, Henri’s ‘exorcists’ had demonstrated that any efficacy exorcism has is due to the placebo effect. Today, when people are concerned enough to call in an exorcist, their willingness to assume that it will work is often enough in itself to ensure that it does. But although placebo is now an acceptable rational explanation, rationality owes its ability to discern the placebo effect to the methods and procedures of the exorcists.

A recent study of the methods of Christian exorcists in present-day North America gives an equally interesting insight into the mind-set on the other side of the fence.

The study surveyed 170 and interviewed in detail 15 Christian exorcists of various denominations, uncovering that although exorcism might be carried out more commonly than we would expect (the exorcist with the least experience had dealt with 11 cases; the most experienced dealt with 1,000), it rarely involves the props of holy water, oil and crucifixes, and there is now a special emphasis on follow-up work, which aims to keep the subject in touch with the church in order to prevent future recurrence.

Nowhere in the study is there any mention of ‘ghosts’ or ‘paranormal phenomena’. Because although non-religious people might consider the church a natural ally against paranormal activity, Christianity awards very little credence to ‘ghosts’. Dead people are viewed as awaiting Judgement and as being unable to return to earth. Passages concerning exorcism in the Bible instead deal exclusively with demons. These are beings created by but which no longer serve God, whose aim is to destroy human beings by leading them into sin and delusion.

The approach of the Christian exorcist and the rational investigator are oddly similar – at least in respect of the reluctance of either to rule out natural explanations, and their shared sensitivity to the possible role of misperception (or delusion). For instance, if someone were to report sightings of a dead relative, the Christian assumption (barring any natural explanation) might be a demonic influence seeking to torment the bereaved person.

The crucial difference, of course, is that whereas the exorcist might blame the tendency toward delusion onto a supernatural agency, the rational investigator considers human misperception in itself a sufficient cause.


Ted J. Kaptchuk, Catherine E. Kerr & Abby Zanger (2009). The art of medicine: placebo controls, exorcisms, and the devil. The Lancet. Vol. 374 (October 10).

Kenneth D. Royal (2012). Investigating the practice of Christian exorcism and the methods used to cast out demons. The Journal of Christian Ministry. No. 4.