“Heresy, Witchcraft, Jean Gerson, Scepticism and the Use of Placebo Controls”, 2023-11-22 ():
Marthe Brossier, a royal commission and Michel Marescot (1539–661605419ya)
In 1599, in a small town in the Loire Valley in France, a young girl with extreme behavioral and verbal outbursts was examined by a medical commission dispatched by Henri IV. It had been alleged that Marthe Brossier was possessed by demons, so she had been subjected to daily exorcisms intended to cast out the demons and restore the girl to health. The exorcisms were performed by priests, often in front of large audiences who came to see the victim’s shocking behavioral displays. The King’s medical commission took Marthe to a private location where her responses to the exorcisms could be closely examined, without distractions.
The backdrop to the King’s medical commission was the violent conflict between Catholics and Protestants in France where demonic possessions were often being used for political purposes. Marthe belonged to a Catholic community and she had become (in)famous because her demons made aggressive claims about Protestants, asserting that they all belonged to Satan. As a powerful tool for the Catholic clergy, Marthe posed a risk to political stability and this prompted the King to send his agents to investigate the truth about her possession.
…The rationale for an exorcism is that a demon cannot tolerate direct contact with divine objects. The exposure to religious paraphernalia would thus cause the demon great pain and force it to leave the possessed person. Marescot and his commission had brought items that would allow them to compare Marthe’s reactions to genuine religious objects and to comparable sham objects. For example, these might include using unconsecrated water in a bottle normally used for holy water, or unconsecrated bread (wafers, or hosts) drawn from a box that usually contained only consecrated bread.
After a 40-day trial, the physicians concluded that Marthe could not have been genuinely possessed by a demon as she reacted similarly when exposed to both genuine and sham religious objects. The commission thus concluded that the allegation that she was possessed was false…Among the trick-trials was one conducted by a Bishop using a sham relic (an ordinary iron key wrapped up the way you would do with a true relic) presenting it to Marthe and telling her that inside was a piece of the true Cross (on which Christ was crucified).
…200 years after Jean Gerson had published his ideas about how to make fair comparisons in witch trials, the use of concealment and placebo controls was ‘repurposed’—from the identification of witches to the identification of charlatans. Anton Mesmer’s claims for the therapeutic value of his ‘animal magnetism’12 were debunked by Antoine Lavoisier, Benjamin Franklin and others.13–16 In 1800, John Haygarth used placebo controls to assess the veracity of Elisha Perkins’s therapeutic claims for this treatment for rheumatism.17,18 At the end of the 18th century, these scientists were acutely aware of the earlier placebo-controlled exorcism trick-trials used by inquisitors in early modern Europe.19 The veracity of genuine relics, consecrated bread and dramatic exorcisms of demons became a contested issue in the early modern era.
As far as we are aware, the writings of Jean Gerson are the earliest written sources describing methodological controls with comparators (such as trick-trials or placebo-controlled trials). The ‘trick-trials’ used to scrutinise alleged demonic possessions in 16th-century France,1 and the debunking of mesmerism13 and of Perkins’ Tractors are early examples of placebo-controlled trials.