Animal magnetism was an 18th-century healing theory based on the idea that an invisible magnetic fluid flows through all living things, and that illness results when this fluid is blocked or out of balance. The concept was developed by German physician Franz Anton Mesmer, and while the magnetic fluid was never scientifically validated, the practices built around it led directly to the discovery of hypnosis and the modern understanding of the power of suggestion. Today, the phrase also lives on as a colloquial way of describing someone with an almost inexplicable physical charisma or presence.
Mesmer’s Theory of Universal Fluid
Franz Anton Mesmer first floated the concept in 1776 under the name “animal gravitation,” borrowing from Isaac Newton’s ideas about gravitational forces acting at a distance. By 1779, he had renamed it “animal magnetism” and laid out its principles in 27 formal propositions. The core claim was simple: a universal magnetic fluid permeated the natural world, connecting humans, animals, and celestial bodies. Health depended on the free flow of this fluid through the body, and disease occurred when the flow was disrupted.
Mesmer developed hands-on techniques to treat patients. He used “magnetic passes,” slow sweeping hand movements directed over the body, to supposedly redirect the fluid toward diseased areas. In group sessions, patients would sit around a large tub filled with iron filings and water, holding iron rods believed to conduct the magnetic force. Many patients reported dramatic responses: convulsions, crying fits, fainting, and, in some cases, relief from their symptoms. These dramatic episodes were called “crises,” and Mesmer considered them essential to the healing process.
How It Accidentally Led to Hypnosis
One of Mesmer’s students, the Marquis de Puységur, stumbled onto something far more interesting than magnetic fluid while practicing animal magnetism in 1784. When he magnetized his servant, a man named Victor, instead of producing the usual convulsive crisis, Victor entered a calm, sleeplike state. He could speak, follow instructions, and even appeared to diagnose illnesses in himself and other patients. But when he woke up, he remembered nothing.
Puységur called this the “tranquil crisis,” later known as artificial somnambulism. What he had actually discovered, without fully realizing it, were the core phenomena of hypnosis: a trance-like state, heightened suggestibility, rapport between practitioner and subject, and spontaneous amnesia afterward. Victor’s behavior during these sessions, including what he and others interpreted as clairvoyance and the ability to predict the course of illness, became foundational case studies. Historians of psychiatry now consider Puységur’s 1784 memoir one of the earliest documented explorations of the unconscious mind, and some scholars call it the true origin point of hypnosis as a practice.
The Royal Commission That Debunked It
Animal magnetism became enormously popular in Paris in the early 1780s, which made the French scientific establishment nervous. In 1784, King Louis XVI appointed a Royal Commission to investigate. The panel was stacked with intellectual heavyweights, including Benjamin Franklin, then the American ambassador to France, and Antoine Lavoisier, the father of modern chemistry.
The commissioners faced an immediate problem: the magnetic fluid was, by definition, invisible and intangible. It had no measurable physical properties and couldn’t be detected by any of the senses. The only way to observe it was through the effects it supposedly produced in patients. So the commission designed a series of controlled experiments, some of which are now considered early examples of blinded trials. In one test, patients were told they were being magnetized when they weren’t, and they still experienced dramatic physical reactions. In another, patients were magnetized without their knowledge and felt nothing at all.
The conclusion, made public on August 11, 1784, was unambiguous. The commissioners declared animal magnetism “une invention illusoire, vaine et funeste” (an illusory, vain, and dangerous invention). The effects patients experienced were real, but they came from the power of suggestion and imagination, not from any magnetic fluid. Franklin himself had already suspected the cures were psychological in nature. This was one of the first times a scientific body formally identified what we now call the placebo effect as the explanation for a medical treatment’s apparent success.
Why the Phrase Stuck Around
Despite being scientifically dismantled in the 18th century, “animal magnetism” entered everyday language as a metaphor for personal allure. When someone says a person “has animal magnetism,” they mean a raw, physical attractiveness that feels almost like a force of nature. The metaphor works precisely because of Mesmer’s original claim: that some people radiate an invisible energy that draws others in and exerts influence over them. The idea that charisma operates like an unseen force, pulling people in without their full awareness, maps neatly onto Mesmer’s framework, even though the literal theory was debunked centuries ago.
Mesmer’s name also gave us the word “mesmerize,” meaning to captivate or hold someone’s attention completely. It’s one of the rare cases where a discredited scientific theory left a deeper mark on language and culture than it ever did on medicine.
What Modern Science Says
No biological magnetic fluid exists. The human body does generate extremely weak magnetic fields from the electrical activity of the heart and brain, but these are millions of times weaker than a refrigerator magnet and have no demonstrated healing properties. Mesmer’s specific claims about a universal fluid connecting all living things have no support in physics or biology.
What does hold up is the underlying mechanism the Royal Commission identified: suggestion. The placebo effect is now one of the most extensively studied phenomena in medicine, and hypnosis, the direct descendant of Puységur’s “artificial somnambulism,” is a recognized therapeutic tool used in pain management, anxiety treatment, and behavioral change. Mesmer was wrong about the cause, but he accidentally demonstrated something genuinely powerful about the relationship between belief, expectation, and physical response in the human body.