When Benjamin Franklin Proved Hypnosis Works

Franz Anton Mesmer was a showman, a medical con artist, a self-promoter of the highest order, and the person most historians credit with laying the foundations of modern hypnosis. He wore lilac robes. He played a glass armonica during treatments. He convinced the wealthiest families in pre-revolutionary Paris that he could cure their ailments by waving his hands over a tub full of iron filings. He was, by almost any modern standard, a fraud. He was also more right than anyone would realize for another two hundred years. And the man who proved it, entirely by accident, was Benjamin Franklin.

The Showman

Mesmer arrived in Paris in 1778 with a medical degree from the University of Vienna and a theory that would make him both famous and infamous. He proposed that an invisible universal fluid, which he called "animal magnetism," governed the health of all living organisms. Disease was a blockage of this fluid. The cure was a trained practitioner who could manipulate its flow through physical "passes," force of will, and proximity to magnetized objects.

The theory was nonsense. The fluid did not exist. But the treatments worked, and that was the problem.

Mesmer's sessions were designed for maximum theatrical impact. Patients gathered around the "baquet," a large wooden tub filled with iron filings, ground glass, and bottles of "magnetized" water. Iron rods protruded from the lid, and patients grasped them or pressed them against their afflicted body parts. Mesmer moved through the room in his robes, making sweeping gestures, staring into patients' eyes, occasionally touching them on the forehead or abdomen. A glass armonica played eerie, wavering tones in the background. The room was dimly lit. The atmosphere was carefully controlled.

The intended result was the "crisis," a violent physical reaction that Mesmer believed signaled the moment the magnetic fluid broke through its blockages. Patients convulsed, shrieked, wept, fainted, and in many cases reported feeling dramatically better afterward. Mesmer treated thousands of patients. He charged the wealthy and treated the poor for free. His waiting list was months long. Paris was obsessed.

The medical establishment was furious.

The Commission

By 1784, Mesmer's popularity had become a political problem. The Faculty of Medicine in Paris had rejected his requests for formal investigation, but public demand and royal curiosity forced the issue. King Louis XVI appointed two commissions to determine, once and for all, whether animal magnetism was real.

The lead commission was extraordinary. Its chairman was Benjamin Franklin, then serving as the American ambassador to France and one of the most famous scientists in the world. Its members included Antoine Lavoisier, the father of modern chemistry, Joseph-Ignace Guillotin (whose name would soon be attached to a very different device), and several prominent physicians. This was not a cursory review. It was the Enlightenment's A-team, assembled to apply the scientific method to Mesmer's claims.

The commission did not actually investigate Mesmer himself. Mesmer had refused to cooperate, sensing the outcome. Instead, they examined the practice of Charles d'Eslon, Mesmer's most prominent student and a respected physician in his own right. D'Eslon practiced the same techniques and claimed the same results.

The Tests

What Franklin and his colleagues designed was, by the standards of 1784, remarkably sophisticated. They understood that the question was not whether patients felt better after treatment. That was already established. The question was whether the magnetic fluid was the cause. To answer it, they needed to separate what patients believed was happening from what was actually happening. They needed blind tests.

In the Blindfold Test, subjects were blindfolded and told they were being magnetized by d'Eslon. Some actually were. Some were not. The results were unambiguous: subjects reacted when they believed the operator was present, regardless of whether he actually was. A woman told she was being magnetized from behind a door experienced a full crisis. When d'Eslon was actually present but the subject did not know it, nothing happened.

In the Tree Test, conducted in Franklin's own garden in Passy, a young man known to be highly responsive to magnetism was led to a series of trees. He had been told that one specific tree had been magnetized by d'Eslon. He was asked to embrace each tree in sequence and report what he felt. At the first tree (not magnetized), he began sweating. At the second (not magnetized), he felt dizziness and pain. At the third (not magnetized), his symptoms intensified dramatically. At the fourth tree, twenty-four feet from the one that had actually been magnetized, he collapsed into a full crisis and had to be carried to the grass to recover. He never reached the magnetized tree.

In the Water Test, subjects were given cups of water, some of which had been "magnetized" by d'Eslon and some of which were ordinary. Again, subjects reacted based entirely on what they were told, not on what was in the cup. Ordinary water presented as magnetized produced powerful physical responses. Magnetized water presented as ordinary produced nothing.

The Conclusion They Drew

The commission's report, published on August 11, 1784, was definitive: the magnetic fluid did not exist. The effects observed in Mesmer's and d'Eslon's treatments were produced entirely by "imagination." The commissioners also noted that physical touch and emotional intensity played a role, and in a separate secret report delivered only to the King, they warned of the "danger to public morals" posed by the intimate physical contact between male magnetizers and female patients during the crisis state.

As a verdict on Mesmer's theory, the report was correct. The fluid was imaginary. No universal magnetic force governed human health. Mesmer's specific claims were wrong.

But as a verdict on what was actually happening in those treatment rooms, the report missed the point entirely.

What Franklin Actually Proved

Read the commission's findings carefully and a different story emerges. The blind tests did not show that nothing happened. They showed that something very real happened, and that the cause was the patient's own mind.

The woman behind the door experienced genuine physiological distress, convulsions and altered sensation, triggered by nothing more than the belief that she was being magnetized. The young man in Franklin's garden collapsed with real, observable symptoms at a tree that had not been treated, because he expected to feel something. The water test subjects reported genuine physical sensations from ordinary water, because they were told it had been prepared.

In every case, the commission documented that belief and expectation, delivered in the right context by a figure of authority, could produce measurable physical effects in the human body. Convulsions. Fainting. Pain relief. Altered sensation. These were not performances. The subjects were not faking. The commissioners acknowledged this. They simply categorized the mechanism as "imagination" and treated that as a debunking.

What they had actually produced was the first controlled experimental evidence of the power of suggestion. Two centuries before fMRI machines would confirm that hypnotic suggestion produces measurable changes in brain activity, Franklin's commission documented the same fundamental phenomenon: that the human mind, given the right conditions of belief, authority, and expectation, can alter its own physical experience. They proved that the mechanism was real. They just did not think the mechanism mattered.

The Aftermath

Mesmer left Paris within a year of the report's publication, his reputation in ruins. He spent his remaining decades in relative obscurity, dying in 1815 in Meersburg, Germany. The medical establishment considered the matter closed.

But the phenomena did not go away. Mesmer's students, particularly the Marquis de Puysegur, had already discovered something that Mesmer himself had overlooked. Instead of the violent "crisis," Puysegur found that some patients entered a calm, lucid, sleep-like state in which they could speak, follow complex instructions, and appeared to have heightened cognitive abilities. He called it "artificial somnambulism." It was the first clinical description of the hypnotic trance as we recognize it today, and it had nothing to do with magnetic fluid, iron rods, or lilac robes.

It would take another sixty years before James Braid in Manchester gave the phenomenon a proper scientific name. It would take another 150 years after that before neuroimaging confirmed what Franklin's commission had stumbled onto in 1784: that suggestion, delivered under the right conditions, produces genuine, measurable, physiological changes in the human brain and body.

Mesmer was wrong about nearly everything he believed. He was right about the one thing that mattered: that something real was happening in those treatment rooms. Franklin was right about what was causing it. He was wrong about whether it was important. Between the two of them, in a series of elegant experiments conducted in a garden outside Paris in the summer of 1784, they produced the foundational evidence for the science of hypnosis. Neither one of them knew it.