Mesmer Royal Commission (1784): Franklin Tests Mesmerism

The Mesmer royal commission of 1784 was an official French investigation into animal magnetism, the fashionable healing system of the German physician Franz Anton Mesmer. Appointed by Louis XVI and including Benjamin Franklin and Antoine Lavoisier, the commissioners ran careful experiments in Paris and Passy. Their verdict, that the effects came from the imagination rather than a hidden fluid, is remembered as a landmark in testing medical claims.

Mesmer and animal magnetism

Franz Anton Mesmer (1734–1815) trained in medicine at Vienna, where his 1766 thesis discussed the influence of the planets on the human body. In the 1770s he began treating patients with magnets and then with his hands alone. He argued that a subtle, invisible fluid filled the universe and flowed through every living body, and that disease arose when its flow was blocked.

After a controversial case in Vienna involving the blind pianist Maria Theresia von Paradis, Mesmer moved to Paris in February 1778. In 1779 he published a short memoir setting out 27 propositions about his “discovery”. Parisian society embraced him. Patients, many of them wealthy, gathered around the baquet, a large wooden tub filled with water and iron filings, from which iron rods projected for patients to touch.

Sessions were dramatic. Soft music played, assistants made passes with their hands, and some patients fell into “crises” of shaking, crying or fainting, which Mesmer considered a necessary step to a cure. In 1783 his supporters Nicolas Bergasse and Guillaume Kornmann founded the Society of Harmony, whose members paid large fees to learn the secret.

Why the king ordered an inquiry

The medical establishment regarded Mesmer as a charlatan, and his growing popularity worried the government. In March 1784 Louis XVI appointed a commission drawn from the Academy of Sciences and the Faculty of Medicine of Paris. A second commission of the Royal Society of Medicine was set up shortly afterwards, in April.

The Academy commission was remarkable. Its members included Benjamin Franklin, then the American minister to France and Europe’s most famous electrical experimenter, the chemist Antoine Lavoisier, the astronomer Jean-Sylvain Bailly and the physician Joseph-Ignace Guillotin. Mesmer refused to take part, so the commissioners studied the practice of his former disciple Charles Deslon, a member of the Faculty of Medicine.

The experiments

The commissioners first tried to detect the fluid itself. It could not be seen, felt or measured with any instrument. They then underwent magnetisation themselves and felt nothing unusual, so they turned to the key question: did the effects depend on magnetism or on what patients believed was happening?

Many trials took place at Franklin’s house in Passy, outside Paris. Subjects were blindfolded and told they were being magnetised when they were not, or magnetised without being told. Reactions followed belief, not the actual procedure. In a famous test a boy was led blindfolded to trees in Franklin’s garden, one of which Deslon had magnetised. He grew dizzy and fainted at a tree that had not been treated.

Other subjects drank from cups or touched objects they were told had been magnetised and reacted strongly, while genuinely “magnetised” items given without their knowledge produced nothing. For the commissioners, the pattern was clear.

The verdict

The report, written by Bailly and signed on 11 August 1784, concluded that there was no evidence for animal magnetism as a physical fluid. The commissioners attributed the crises to imagination, imitation and the effects of touch. They warned that the convulsive scenes around the baquet could be harmful. A separate confidential report to the king raised concerns about the moral risks of intimate treatments given by male magnetisers to women patients.

The report was printed in large numbers and widely read. The Royal Society of Medicine commission reached a similar conclusion, though one member, the botanist Antoine-Laurent de Jussieu, issued a dissenting opinion arguing that touch could have real effects.

Consequences and legacy

The reports damaged Mesmer’s reputation, and he left Paris around 1785. He spent his later years in Switzerland and Germany and died at Meersburg on Lake Constance in 1815. His followers, however, did not disappear. In 1784 the Marquis de Puységur described a calm “magnetic sleep” in which patients seemed to talk and act while entranced, and magnetism societies spread across France.

That trance state was the root of later hypnotism, named by the Scottish surgeon James Braid in the 1840s, who explained it without any fluid. Historians such as Robert Darnton have also shown how mesmerism mixed with radical political ideas in the years before the French Revolution.

The fates of some commissioners were tragic. Bailly became mayor of Paris in 1789 and was guillotined in 1793, and Lavoisier, whose work is described in Lavoisier and the Chemical Revolution, was executed during the Reign of Terror in 1794. Guillotin’s name became attached to the execution machine, though he did not invent it.

Myths and facts

A common claim is that the commission proved Mesmer’s patients were faking. In fact the commissioners accepted that the reactions were real; they denied only that a magnetic fluid caused them. Another myth is that Franklin led every session. He was ill with gout and many trials took place at his home, but the report was drafted by Bailly. Franklin had a long record with electricity, seen in his kite experiment, which made his judgment widely respected.

Timeline

• 1766: Mesmer completes his medical thesis in Vienna.
• 1778, February: Mesmer arrives in Paris.
• 1779: Mesmer publishes his memoir with 27 propositions on animal magnetism.
• 1783: The Society of Harmony is founded to teach Mesmer’s method.
• 1784, March: Louis XVI appoints the royal commissions.
• 1784, 11 August: The Academy commission’s report, written by Bailly, is signed.
• 1785: Mesmer leaves Paris.
• 1815, 5 March: Mesmer dies at Meersburg.

Why it matters

The 1784 commission was one of the first organised attempts to test a medical treatment with blinded trials. By separating belief from physical cause, it described what medicine now calls the placebo effect, and its method remains a model for testing extraordinary claims.