Mesmerism is the practice of “animal magnetism” invented by the physician Franz Anton Mesmer in the eighteenth century. Mesmer claimed that an invisible fluid ran through the universe and through the human body, and that illness came from a disturbance in its flow. He treated patients by touch, gesture and group sessions around a tub called the baquet, and many of them fainted or convulsed in what he treated as a curative “crisis.”
In 1784 a royal commission in Paris, led by Benjamin Franklin, tested the claim with experiments that were unusually careful for their day. The commissioners’ report survives in English. Reading what they actually did is better than any summary, and it shows that the story “Franklin debunked Mesmer” is accurate but incomplete.
Who Mesmer was and what he claimed
According to the historian-of-science essay by Urte Laukaityte in The Public Domain Review, Mesmer built a practice among upper-class patients in Vienna before falling into disfavor, and by 1778 he had moved to Paris. The medical profession there refused him a license, so he partnered with a licensed physician, Charles Deslon, the personal doctor to the king’s brother. His theory held that a special imperceptible magnetic fluid pervaded the universe and that most diseases came from an abnormal flow of it in the body. At first he used magnets; later he found that his hands or other objects worked just as well.
The commissioners’ own report quotes Mesmer’s description of the agent: a fluid universally diffused and a vehicle of mutual influence between bodies. The Public Domain Review essay describes the typical group session: patients seated around the tub, touching iron rods, linked by a rope, in a dim room with mirrors and music, and ending with a “crisis” of hiccups, sobs, coughing and fainting. The report describes the same crises, and attributes their spread partly to imitation.
The 1784 commission
The 1785 English translation of the report states that on 12 March 1784 the king named four physicians of the Paris faculty to examine and report on “the animal magnetism practised by M. Deslon,” and that at their request he added five members of the Royal Academy of Sciences: Franklin, Le Roy, Bailly, de Borie and Lavoisier. One commissioner died early and was replaced by the physician Majault. The report is dated Paris, 11 August 1784, and is signed by Franklin, Majault, Le Roy, Sallin, Bailly, d’Arcet, de Bory, Guillotin and Lavoisier.
Note what was examined: Deslon’s practice, plus some trials with another magnetiser, a Monsieur Jumelin, not Mesmer’s own sessions. That limit matters when people say the commission “debunked Mesmer.” It tested the claim of a magnetic fluid as these practitioners presented it, and its conclusions are about that fluid.
What the commissioners did
Sick patients at Franklin’s house. The commissioners had seven patients from the lower class treated by Deslon at Franklin’s house in Passy, with all the commissioners present. They then ran further trials. The report tallies the results across fourteen sick persons: five appeared to feel some effect and nine felt none. It also says one commissioner who had a headache and cold feet derived no benefit.
The blindfold test. In trials with Jumelin, the commissioners blindfolded a woman whose sensitivity to the treatment seemed established, so she could not know what was being done. The report says that once she was blindfolded the effects no longer matched the places toward which the magnetism was directed. With the bandage on and no operation performed at all, she still experienced the same effects.
The apricot tree. Deslon brought a boy of about twelve who was known to respond. The commissioners picked an apricot tree in Franklin’s orchard, far from other trees, and Deslon “magnetised” it while the boy waited in the house. The boy was then brought out blindfolded and made to embrace four other trees, none of which had been treated, for two minutes each. He reported mounting symptoms at each one, and at the fourth, which was about 24 feet from the magnetised tree, he fell into a crisis and fainted. The commissioners concluded that the crisis could not have a physical external cause, since the tree was not magnetised.
The sham treatment. At Passy, a woman with films over her eyes was blindfolded and told that Deslon had come into the room to treat her. He had not; a commissioner was pretending, and the others sat silent and watched. Within three minutes, the report says, she had a crisis with all the regular symptoms, shuddering, striking her hands together and stamping, which commissioners in the next room heard through a closed door.
The paper partition. A seamstress known to respond strongly to magnetism, Mademoiselle B., had fallen into a crisis in three minutes at Passy. Later she was seated against a paper-covered frame without knowing why, while a physician “magnetised” her from the other side for half an hour in the way Deslon prescribed. She chatted cheerfully and felt nothing. When the same commissioner then came into her room and openly repeated the operation in a direction that the theory said should produce no effect, she reported dejection, suffocation, hiccups and chattering teeth within three minutes.
What they concluded
The commissioners wrote that they had shown “by decisive experiments” that imagination without magnetism produces convulsions and that magnetism without imagination produces nothing. They concluded unanimously that the existence of the fluid was “absolutely destitute of proof,” that a fluid with no existence can have no use, and that the symptoms seen in the public sessions come from compression, imagination and a tendency to imitate. They also warned that the crises were potentially harmful and that watching them was dangerous for the same reason.
Why it matters beyond Mesmer
The experiments were designed so that the subject either received the treatment without knowing it or believed they were receiving it when they were not. The Public Domain Review essay argues that this makes the Franklin commission an early example of blinded, placebo-style testing, and that the commissioners treated suggestion as a rival explanation to the fluid. That is the essay’s reading, not the commissioners’ own vocabulary; the report speaks of “imagination,” not placebo.
The same essay adds that two reports were written in 1784, one public and one kept secret for the king’s eyes because of its “indecent” elements, and that the report raised moral concerns about the setting, in which a male magnetiser treated mostly female patients at very close range. It also argues that although the fluid did not survive, animal magnetism marked the beginnings of hypnosis and psychological suggestion.
What the commission did not show
- It did not show patients felt nothing. The report treats the sensations and crises as real events in the patients’ bodies and attributes them to imagination, touch and imitation. It does not say the patients were lying; it uses the phrase “real or pretended” and does not try to settle which.
- It did not test every claim of cure. The experiments were short trials on a small number of people. They address whether a physical fluid was acting, not what happened to patients over months.
- It tested Deslon’s practice. Mesmer’s own sessions were not the subject of these experiments.
- Part of what we know comes secondhand. We have the report in a 1785 English translation. The Public Domain Review essay is a modern interpretation, and we cite it as such.
The story did not end in 1784. The Marquis de Puységur, a follower of Mesmer, defended animal magnetism in a memoir the same year; the modern English edition of that memoir carries the phrase “artificial somnambulism” in its title, naming the trance-like state he reported. We keep the sources for that on Puységur’s Animal Magnetism Files. For another example of how easily attention and expectation shape what people report seeing, read our guide to change blindness.
Common questions
What is mesmerism?
Mesmerism is the practice of animal magnetism developed by Franz Anton Mesmer, who held that a universal magnetic fluid in the body could be redirected to heal disease. Patients were treated by touch and gesture, often in groups around a tub called the baquet.
Who investigated Mesmer’s claims in 1784?
A royal commission appointed by the king of France, including Benjamin Franklin, Jean-Sylvain Bailly and Antoine Lavoisier, examined the animal magnetism practised by Charles Deslon. It reported on 11 August 1784.
What did the Franklin commission find?
It found no evidence that a magnetic fluid existed and concluded the crises and sensations came from imagination, touch and imitation. In its experiments, subjects showed effects when they believed they were being treated but nothing was done, and none when they were treated without knowing it.
Is mesmerism the same as hypnosis?
Not exactly. Mesmerism was built on a theory of a magnetic fluid that the commission rejected. A modern essay on the commission argues that animal magnetism marked the beginnings of hypnosis and psychological suggestion, so the two are historically linked.
Sources & Further Reading
- Report of Dr. Benjamin Franklin, and other commissioners, charged by the King of France, with the examination of the animal magnetism, as now practised at Paris (London: J. Johnson, 1785) — full English text on Project Gutenberg. Primary source for the commission’s membership, experiments and conclusions.
- Urte Laukaityte, “Mesmerising Science: The Franklin Commission and the Modern Clinical Trial,” The Public Domain Review (20 November 2018) — modern interpretive essay; source for Mesmer’s career outline, the session description, the secret report and the link to modern trial design.
- Final Vestige, Puységur’s Animal Magnetism Files — our source files on Puységur’s 1784 memoir.
- Wikimedia Commons: “Le Baquet de Mesmer,” Wellcome Collection — CC BY 4.0.
