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The Glass Delusion of the Late Middle Ages

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King Charles VI's glass delusion

King Charles VI's glass delusion

The Glass Delusion

A strange affliction passed through the ranks of European nobility starting in the late Middle Ages—the conviction by some that they were made of glass. Sufferers believed they were in danger of shattering into thousands of small pieces.

King Charles VI

King Charles VI

Charles VI of France

One of the earliest recorded cases of the glass delusion was a boy who ascended to the throne of France at the age of 11. Charles VI became king in 1380 and was known as both Charles the Beloved and Charles the Mad, with the latter nickname being a reflection of his mental health problems.

In 1392, Charles was struck by the first bout of insanity. While riding with his retinue, he flew into a rage and killed several companions with his sword. His courtiers were able to subdue him, but the psychotic episodes continued. In one, he forgot his own name; in another, he believed he was St. George. Then came the glass delusion.

Convinced he was made entirely of glass, he had metal rods sewn into his clothing to protect him from accidental bumps. He wrapped himself in thick blankets and remained perfectly still for hours at a time. When he did move, he did so with great caution.

Charles, of course, did not shatter like a fragile goblet; he died of malaria in 1422 at the age of 53. It’s widely assumed that Charles suffered from schizophrenia.

How did this belief spread?

How did this belief spread?

The Delusion Spreads

The malady that afflicted Charles soon began to show up among the ruling classes of Europe, and nobody knows for sure why this happened. Two prominent 16th-century physicians, Alfonso Ponce de Santa Cruz and Andre du Laurens, studied the phenomenon. They wrote about a royal, who they did not name, who had straw piled up in his living quarters in case he fell or stumbled.

Other members of the aristocracy were convinced they had glass body parts―feet, hearts, and even heads. Among males, a fear of having glass buttocks was quite common; the treatment for this ailment was to have pillows tied to their bums. Nicole de Plessis, a relative of Cardinal Richelieu, was one of those who believed he had a glass rear end.

Having a fragile rump presented certain difficulties that were not always immediately apparent. Those with the condition would not sit down without a fluffy cushion to protect their bottoms from turning into shards of glass. So, eliminating waste was a serious issue, but we don’t need to go into graphic detail.

There are stories of physicians using a tough-love cure for the glass derriere malady; a few powerful whacks with a stick convinced some sufferers they were not as breakable as they thought.

“We are all glass men, subjected to innumerable dangers. The slightest touch would break us, and we would return to nothing.”

— Giovanni Boccaccio (14th-century poet)

Delusion Connected to Innovation

Edward Shorter is a historian of psychiatry at the University of Toronto. He says the glass delusion is not unique and fits in with a pattern of similar complaints that are tied to the creation of new technologies.

History notes that when Charles VI was having his delusions, “glass—particularly clear glass—was a precious, novel commodity, mostly found in royal palaces, churches, and government buildings.”

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Before the glass delusion, there was a spell when some people suffered from the belief that they were made of earthenware. In the 19th century, the new miracle material was concrete, so people started believing their bodies were constructed out of cement, sand, and gravel.

The digital age has created a new crop of delusions; a quick internet search turns up plenty of people who are convinced that the government, or some other entity, has implanted tracking and thought-control devices in their brains.

The Phenomenon Explained

Psychiatrists are reluctant to diagnose mental illnesses without examining the patient, and, as Charles VI and other sufferers of the glass delusion have long since died, clear diagnoses are not possible.

By the middle of the 19th century, cases of the glass delusion all but disappeared, although a doctor in the Netherlands has uncovered a few contemporary cases. Psychiatrist Andy Lameijn has described treating a young man who had recovered from an accident only to develop the belief he was made of glass. The patient said he had the ability to turn himself into glass at will so he could “disappear.”

According to the BBC, Dr. Lameijn’s “conclusion was that the man in question was using this glass delusion as a sort of distance regulator―following the accident, his family had become over-protective, and the glass delusion was an attempt to regain privacy and hide from overbearing family.”

Psychoanalyst Adam Phillips postulates that the condition is an extreme manifestation of anxiety. This fits in with theories about how the delusion hit the nobility several centuries ago. People in positions of leadership had a profound fear of appearing vulnerable, although deep inside, that’s likely exactly how they felt. The result was a massive overdose of anxiety that surfaced as the belief that they were made of fragile glass.

In 2015, The Paris Review noted that “The glass delusion has powerful contemporary resonance in a society in which anxieties about fragility, transparency, and personal space are pertinent to many people’s experience of, and anxieties about, living in the modern world.”

Bonus Factoids

  • In 1613, Miguel de Cervantes published a novella under the title The Glass Candidate (El Licenciado Vidriera). It tells the story of Tomas, whose girlfriend gives him a dodgy love potion. Instead of turning him into the paramour a woman dreams of, the drink turns Tomas into a man who believes himself to be made of glass. Tomas became reclusive and almost starved to death before overcoming his delusion. Cervantes did not, however, deliver a happy ending. Poor Tomas joined the army and died in a battle.
  • The Dutch poet Constantijn Huygens also had a go at fictionalizing the glass delusion. He wrote that the central character in his work “fears everything that moves in his vicinity . . . the chair will be the death for him, he trembles at the bed, fearful that one will break his bum, the other smash his head.”
  • The Anatomy of Melancholy was published in 1621. The author, Robert Burton, wrote about people agonizing “that they are all glass, and therefore will suffer no man to come near them.”


  • “The People Who Think They Are Made of Glass.” BBC Magazine, May 8, 2015.
  • “The Delusion that Made Nobles Think Their Bodies Were Made of Glass.” Hadley Meares,, August 29, 2018.
  • “The Glass Delusion.”, February 4, 2020.
  • “Nobles Used to Suffer from ‘The Glass Delusion’ and Were Terrified of Breaking.” D.G. Hewitt,, undated.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2020 Rupert Taylor


Miebakagh Fiberesima from Port Harcourt, Rivers State, NIGERIA. on June 11, 2020:

People can think and believe anything their think their are made of. This thinking actually emerged when man realized he was dust and ash. But for an individual to think he/she is glass/mirrow is beyound the imagination and too weird. It must be a sign of mentaf imbalance. The most realistic thing to ponder is that you are water.

Ann Carr from SW England on June 11, 2020:

Fascinating! I'd never heard of this. I now understand the thinking behind such a delusion but I find it weird that someone would think they're actually made of glass.

You always manage to find unusual aspects of life and your presentation is educational yet humorous, so always a great read.


Miebakagh Fiberesima from Port Harcourt, Rivers State, NIGERIA. on May 23, 2020:

Rupert, I've never heard it nor read about it. Thanks for sharing.

Rupert Taylor (author) from Waterloo, Ontario, Canada on May 22, 2020:

When I stumbled on this Rochelle I thought it must be a prank, but, it turns out it was and is a real condition.

Rochelle Frank from California Gold Country on May 22, 2020:

Never heard of this before, but it makes some sense in a way. Humans are incredibly fragile in some ways and can even be shattered by an invisible virus. Sometimes even the rich and powerful can realize their vulnerability. Having a glass behind would be particularly inconvenient. Very interesting stuff, Rupert, as always.

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