You might have used the term “animal magnetism” to describe the je ne sais quoi that allows only a lucky few people to consistently charm the pants off their audiences, literally or figuratively.

According to the term’s 18th-century inventor, animal magnetism is a very real thing that exists in all of us as a magnetized liquid—one that empowers us, of course, but that can also form dangerous clots that will give your cosmic alignment the spins.

To understand the theory of animal magnetism, its cultural impact, and just how the latter managed to be so big, we’ll start with a quick time-and-space hop to where the pseudoscientific craze really caught on: pre-revolutionary Paris.

THE CITY OF LIGHT, LOVE, AND ANIMAL MAGNETISM

It was the turn of the swingin’ 1770s. The French (in large majority) were suffering under worsening food shortages and a growing financial crisis; Marie Antoinette was spending ever more time fabulously entertaining guests at the Petit Trianon in Versailles (her favorite niche in a palace that employed 10,000 for upkeep); French fashions, architecture, furniture, and writings were taking the continent by tempête.

The curtains were also coming down on the Enlightenment era, much of which found its legs in the cafes, salons, and clubhouses of the French capital. Critic Stephen Jay Gould points out that, when it came to brand new ideas, Paris was “the most 'open' and vibrant capital of Europe” at the time—a city that “[embraced] intellectual ferment of the highest order combined with quackery at its most abject: Voltaire among the fortune tellers; Benjamin Franklin surrounded by astrologers; Antoine Lavoisier amidst the spiritualists."

Enter German physician Franz Anton Mesmer, who’d left Vienna (where he’d been in hot water over failing to cure—and likely seducing—a young, blind pianist) and traveled to Paris in 1778 with his distinctive charm, private money, and seemingly innovative ideas in tow.

WHO IS THIS GUY, AND WHY DOES HE WANT ME TO DRINK IRON FILINGS?

Prior to his arrival in Paris, Mesmer had already mostly developed his grand theory, which, “insofar as one can find coherence in his ideas at all,” Gould says, “claimed that a single (and subtle) fluid pervaded the universe, uniting and connecting all bodies." This unifying fluid had different names depending on its context: the planets orbited according to its force in the form of gravity, its manifestation as simple magnetism determined a compass’ course, and, as the fluid that flowed in all living things, it was called “animal magnetism.”

While this “subtle” fluid couldn’t actually be extracted and studied, it was thought to nevertheless affect the human body in a big way. Mesmer argued that blockages in a person’s magnetic flow could cause any number of diseases and conditions, ranging from the physical and the psychological to the simply intangible (many of his disciples also later suggested these blockages were the only cause of illness).

To remedy magnetic imbalances and blockages, Mesmer and subsequent trained practitioners (or “mesmerists”) treated patients in several different ways. In a one-on-one session, Mesmer would locate the magnetic “poles” on a person’s body (something he could do thanks to his own “unusually strong magnetism,” Gould says). He would then touch, hold, or massage the parts of the patient’s body that contained those poles in order to discharge excess energy and/or restore balance—often while staring deeply into her eyes (most of his patients were women, but not all). In some cases, he’d prescribe his patients to drink “magnetized” water that contained iron filings, or pass magnets over their bodies.

He also developed cost-effective group treatments for righting personal magnetic imbalances en masse. In a salon setting, Mesmer would instruct as many as 20 people to each take a thin metal rod from a baquet (or vat) of supposedly magnetized water—sometimes garnished with metal shavings—and pass it over their body’s poles. If the gathering were larger than 20, Gould reports, he’d “loop a rope from those who surrounded the baquet (and held the iron rods) to others in the room [...and] then instruct the roped group to form a ‘mesmeric chain’ by holding a neighbor’s left thumb between their own right thumb and forefinger,” thereby letting magnetic impulses flow through the entire linked group.

Not to be accused of only using his treatment for profit among the wealthy, Mesmer also reportedly “magnetized” a number of trees so that lower-class sufferers of illness could touch them at their leisure and discharge any surplus magnetism.

DID IT WORK?

There are many semi-documented cases (mostly by Mesmer himself) of patients who seemed to recover after receiving mesmeric treatments. However, science-minded individuals at the time and in the centuries since have suggested that any positive effects from his services should be credited not to magnetism but rather to psychological means, i.e. psychosomatic healing through the power of suggestion. Dr. Mesmer certainly seemed to encourage this, using not just his palpable charm but also well-placed mirrors and “music played on the ethereal tones of a glass harmonica, the instrument that Benjamin Franklin had developed," to heighten the effect.

Mesmerism definitely had an observable impact, though. After receiving treatment, some patients (mostly women) would enter a frenzied state, flailing and moaning as their bodies’ animal magnetism levels redistributed. Mesmer encouraged this, and even provided softly furnished “crisis rooms” where guests—delivered there by a team of assistants—could comfortably work through their mesmeric fits. It was this sort of joyous, freeing hysteria brought on by mesmeric treatments that also led a good portion of Mesmer’s many critics to suspect his practice of promoting a very unseemly, unbridled female sexuality that just wouldn’t do (that, and all the knee-cupping).

Ultimately, two commissions appointed by King Louis XVI unequivocally rejected the science of Mesmer’s animal magnetism (with Benjamin Franklin, inventor of the glass harmonica, sternly sitting on the second), and the practice had effectively faded away in France by the end of the decade. The infection had already taken hold, however, and dedicated mesmerists continued touting the benefits of well-managed animal magnetism elsewhere in Europe ‘til the early 1850s.

ONE LAST MAGNETIC DISCHARGE

Gould points out that "wrenching a person from his own time and judging him by modern standards and categories" isn't particularly fair or useful, especially when taking into account the fact that "the lines between science and pseudoscience were not so clearly drawn in Mesmer's time." Due to few records on the German doctor having survived, we just don't know "whether he was a simple charlatan, purveying conscious fakery for fame and profit, or a sincere believer, deluded no less than his patients."

Mesmerism’s also had lasting benefits and worth to scholars in various disciplines as either a forerunner, a counter-balance, or simply a case study; it’s provided food for thought for a wide range of philosophers, historians, and psychologists, and even led to the development of a statistically more useful practice that lives on today: hypnotism.

And if, despite generations of naysayers throughout the sciences, you’re still intrigued enough by the idea to want to try it out, there’s probably no harm in linking thumbs with friends, touching trees, or getting a particularly magnetic pal to massage your knees; stay away from the iron-filing cocktails, though.