Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking

D.G. Hewitt - November 25, 2019

Towards the end of the Middle Ages, something strange started happening across Europe. People started believing they were made from glass. They firmly believed that they could shatter if touched. This became known as the “glass delusion”, and most cases involved the rich and the powerful. But what caused this strange phenomenon? And why did it disappear almost as swiftly as it appeared? Here are 30 things you need to know if you want to understand the bizarre history of the glass delusion…

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
The King of Spain was all-powerful – so why did he think he was made from glass? Wikimedia Commons.

30. The Glass Delusion made even the most powerful feel fragile and powerless

As the absolute monarch, King Charles VI, was the most powerful man in all of France. He ruled over a kingdom of millions for 42 years, one of the longest reigns in French history. He led his armies into battle against the English during the Hundred Years War and played a key role in shaping the European political landscape of the time. However, Charles felt far from powerful. In fact, he truly believed he was made of glass and could shatter at any moment. And the truly weird thing? Charles wasn’t the only one to suffer from the “Glass Delusion”.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Europe in the Middle Ages was full of superstition and strange beliefs. Wikimedia Commons.

29. The delusion swept across Europe at the end of the Middle Ages, though no one can say for certain how it began

Nobody knows for sure when this bizarre psychiatric phenomenon began. Or indeed what was behind it? But King Charles VI of France was by far the most famous case. By most accounts, the “Glass Delusion” affected certain individuals across Europe from the end of the late Middle Ages into the start of the early modern period (that is between the 15th and 17th centuries). And while the recorded cases may have been spread across the continent, they all had one thing in common: the sufferer firmly believed that they were not flesh and bone, but instead made from fragile glass.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
This medical textbook by Robert Burton tried to explain the glass delusion. Time Out

28. The glass delusion featured in medical textbooks of the time – and was just one of many strange conditions

This particular delusion emerged at a time of heightened anxiety across Europe, especially among the ruling classes. The book The Anatomy of Melancholy, written by the Oxford University scholar Robert Burton and published in 1621, lists the glass delusion as just one of a number of strange beliefs of the time. Indeed, as well as men who worry “that they are all glass”, Burton also wrote of people who believed they were made out of cork. Others believed that they were “as heavy as lead” or had “frogs in their bellies”, while some feared their heads would fall off their shoulders.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
King Charles VI of France became convinced he was made from glass. Wikimedia Commons.

27. King Charles VI of France had absolute power – but felt like he could shatter at any time

To really understand the “Glass Delusion”, it’s best to start with its most famous – or infamous – “victim”. The record shows that Charles VI, who was born in December of 1368, had a relatively normal childhood and adolescence. Indeed, when he ascended to the French throne in 1380, there were no signs that he would soon become known as “Charles the Mad”. But then in his mid-20s, Charles started suffering from bouts of psychosis. Even then, however, the belief he was made from glass had not yet set in.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Charles VI of France gained a reputation for being a “mad” monarch. Wikimedia Commons.

26. A mental breakdown likely triggered King Charles into believing he was made entirely from glass

The King’s first – and most severe – breakdown came in 1392. Sent into a rage by the attempted murder of one of his closest friends, Charles went on a mini killing spree. As well as offing four of his own knights, he also attacked his own brother, the Duke of Orleans. After that, he was never the same. King Charles not only struggled to remember his wife, he also forgot his own name. And, of course, he started to believe he was made of glass. Unsurprisingly, this affected his life in every way.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
King Charles became increasingly reclusive due to his strange glass delusion. Wikimedia Commons.

25. Thanks to his strange delusion, the French monarch soon became known as “Charles the Mad”

King Charles VI’s strange delusion meant that he would never allow anyone – not even his own wife – to touch him. He genuinely feared that if he were manhandled in any way, he could shatter completely. The French King, by now widely known as “Charles the Mad”, rarely left his quarters. When he did venture out, he was terrified of bumping into a door or furniture. To protect himself, he had his tailors reinforce his clothes with extra padding and even steel rods. But not even this would make him feel safe. The monarch’s glass delusion had taken over his life.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Charles VI was far from the only European royal cursed with poor mental health. BBC History.

24. Was the French King’s glass delusion due to severe anxiety? Or schizophrenia maybe?

Charles died in 1422 having never gotten over his delusion. While modern-day healthcare professionals are always wary of diagnosing historical figures, it’s believed that Charles VI suffered from some degree of schizophrenia. Alternatively, some scholars believe that Charles’ glass delusion was the result of severe anxiety or even from the stress that came with being absolute ruler of France. Whatever the reason for it, Charles VI could at least take comfort in the fact that he wasn’t the only one who believed that they were made out of glass.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
The doctors of the time struggled to find cures for the mental health issues of the rich. Wikimedia Commons.

23. Most sufferers of the glass delusion were rich, powerful males, and many may have been faking it to be fashionable

According to the historian Gill Speak, the world’s foremost expert on the ‘glass delusion’, cases of this psychiatric disorder began to spread throughout Europe during the 16th century. Could it be that King Charles VI had made the belief fashionable? Did people genuinely believe they were made of glass, or did they just want to show off their similarities to royalty? Nobody will ever know for sure. But what is apparent is that it was mainly men – and mainly royals or members of the aristocracy – who suffered from this most bizarre of afflictions.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Royal court physicians tried a range of methods to treat cases of glass delusion. Wikimedia Commons.

22. Court physicians across Europe used their knowledge and influence to document cases of the glass delusion

At the start of the 16th century, two of Europe’s foremost physicians took a keen interest in the glass delusion. Andre du Laurens was the personal physician to Henry IV of France, while his friend and colleague Alfonso Ponce de Santa Cruz served in the court of Philip II of Spain. Together, they researched the phenomenon, listening out for cases and comparing notes. Most notably, they recorded the example of an unnamed royal who had a particularly bad case of glass delusion. His story became the stuff of a psychiatric legend.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
The royals of Europe were hit by a wave of mental health issues in the 16th century. Wikimedia Commons.

21. One crazed royal locked himself up in a padded cell to protect his ‘glass’ body from shattering

According to the doctor duo’s notes, as recounted by Speak, the confused royal followed the example of Charles VI and hold himself up in his room. Like the French king, he feared he would shatter if he bumped into something or someone, so he preferred not to take any chances. The poor man even ordered his servants to fill his private quarters with straw so to protect him if he were to accidentally stumble and fall. Before too long, however, the anonymous man’s doctor had enough and decided on that drastic action was needed to shatter his patient’s glass delusion.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Medieval doctors were not exactly known for their gentle bedside manner. Wikimedia Commons.

20. Tough love was often the best cure for the glass delusion – even if it meant setting fire to a royal patient’s private rooms

The exasperated court physician ordered the royal’s guards to set the straw on fire. He then locked the doors to the private quarters. He risked being charged with treason – or even murder should his patient die in the blaze. In the end, the panicked royal, desperate to be saved from the flames, banged on the door, begging to be let out. The clever doctor then asked the royal why, if he was indeed, made of glass, his hand had not simply shattered with all the violent banging.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Spanking a patient’s buttocks might help him see he wasn’t made of glass. Wikimedia Commons.

19. Doctors would try and convince patients of the absurdity of their delusions, including through harsh spanking sessions

And just like that, the delusion was broken. According to Elena Fabietti, another scholar who has researched the glass delusion, the spell was broken as soon as the royal was confronted with the absurdity of his beliefs. Faced with being burned alive, the royal quickly recanted his illogical belief in being made from glass. He reportedly yelled: “Open, I am begging you, my friends and dearest servants. I don’t think I am a glass vase but the most miserable of all men; especially if you will let this fire put an end to my life.”

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Cardinal Richelieu’s relative was a high-profile victim of the glass delusion. Wikimedia Commons.

18. Another of France’s most powerful men was a notable sufferer of the glass delusion

Again, this was not an isolated case of a well-to-do gentleman believing that they were made out of glass. Indeed, several decades after Charles VI had suffered from his glass delusion, the psychiatric disorder was once again seen in France. This time around, the sufferer was Nicole du Plessis. Not only was he rich, he was also incredibly well-connected. Family ties to Cardinal Richelieu, the power behind the French throne, gave him influence and power. Du Plessis should have felt indestructible. Instead, he felt fragile and at risk of being shattered into a million pieces.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Chateau du Breze was the home of Nicole de Plessis, a victim of glass delusion. Pinterest.

17. Like many sufferers, Nicole du Plessis wore padded clothes to protect his ‘glass’ buttocks from harm

Like the French King before him, Nicole du Plessis believed that he was made from glass. Or more specifically, he believed that his buttocks were made from glass. As a result of this, he would carry a large, soft cushion around with him everywhere that he went. He would also keep his distance from other people and, like most other sufferers, wore specially-adapted clothes. Sadly, like most other cases of glass delusion, the story of Nicole du Plessis remains something of a mystery. Nobody knows for certain if he was cured of his delusions – or whether he lived the remainder of his life believing he was made from glass.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Charles VI was one of many sufferers who believed they had glass buttocks. Research Gate.

16. The buttocks were a particularly sensitive area for sufferers of the glass delusion – making everyday life extremely stressful

Curiously, concern over the fragility of the buttocks was quite common among sufferers of the glass delusion. Medical notes dating back to 1561 tell of one man, a resident of the Saint Germain suburb of Paris, who was so convinced that his backside was made of glass that he was even too afraid to sit on a toilet. In the end, a doctor’s tough love cured him of his affliction: rather than pandering to his patient’s whimsy, the physician simply thrashed him, proving that the man’s buttocks were indeed made of human flesh rather than glass.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
The Spanish literary giant Cervantes found inspiration in the glass delusion. Wikimedia Commons.

15. The craziness of the glass delusion understandably inspired the top artists and writers of the time

Though the actual number of sufferers might have been small, the glass delusion nevertheless captured the popular imagination across Europe. Understandably, it inspired many artists, including some of the continent’s finest writers. Miguel de Cervantes, best known as the author of Don Quixote, penned a novella called The Glass Graduate. The Spaniard’s work, which came out in 1613 – arguably at the height of the glass delusion craze – tells the story of a young peasant called Tomas whose dreams of becoming a lawyer are thwarted when his paramour slips him a badly-made love potion.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Cervantes’ tale of a poor man with a glass delusion did not give the reader a happy ending. Pinterest.

14. The author of Don Quixote penned perhaps the most famous fictional account of the glass delusion

Far from arousing his desires, the potion simply makes the protagonist of Cervantes’ story delusional. Before long, he becomes a complete hermit, believing himself to be made entirely from glass. Tomas not only loses his lover, he also loses his career, shuns shoes and clothes and almost starves himself to death out of fear of going outside. The Glass Graduate ends with Tomas becoming a celebrity before regaining his sanity. To escape his notoriety as the ‘glass man of Spain’, he joins the army, only to be killed on the field of battle.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Dutch poet Constantijn Huygens was another artist who addressed the glass delusion. Wikimedia Commons.

13. Poets also used their prose to try and understand the absurdity of the glass delusion sweeping Europe

And it wasn’t just authors who were inspired by the glass delusion. Poets also used the affliction as a subject matter. The most famous example of this is that of the Dutch poet Constantijn Huygens. In his work Costly Folly, which came out in 1622, the protagonist has a serious case of glass delusion. Through his prose, Huygens describes the symptoms in detail. He writes of a man who “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”.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Descartes took things further by exploring the philosophical meaning of the glass delusion. MIT.

12. Renowned philosopher Rene Descartes gave the glass delusion serious consideration in his meditations

As well as inspiring creative types across Europe, the glass delusion also provided the continent’s philosophers with food for thought. Most notable among these was Rene Descartes. The Frenchman was fascinated by the idea of perception and reality. In his landmark 1641 work Meditations on First Philosophy, Descartes used the glass delusion to show that we all perceive the world differently. The book asks the reader to consider the case of an insane man who genuinely believes himself to be made from glass: is his knowledge of the world wrong or simply different to the knowledge of the majority?

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
One of Germany’s top scientists believed he found proof that man could turn to glass. Wikimedia Commons.

11. Scientists were also fascinated by the glass delusion: could it really be possible for humans to be made out of glass, they wondered…

The glass delusion may have emerged as Europe was moving towards the Age of Enlightenment, but some men of science still investigated it thoroughly. The German alchemist Johann Becher was especially fascinated by the phenomenon. In his 1669 work Physica Subterranea, he even went so far as to claim that he had found the secret to turning humans into glass. Or, more specifically, Belcher boasted of knowing how to turn dead bodies into glass objects.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Belcher hoped to find a way of turning human bodies into glass. University of Oregon.

10. The German scientist Johann Belcher believed he found a way to turn dead bodies into beautiful glass objects

Turning cadavers into glass may seem strange, but Belcher had his reasons. He believed that his studies could be of great value to society. That is, he hoped that his research could be used to turn bodies into beautiful glass objects. This way, people could surround themselves with their deceased relatives. Of course, Belcher was very, very wrong. Nevertheless, he was correct in his belief that silicon – the element used to make glass – can be found in the human body, but only in tiny, insignificant amounts.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
From an early age, Princess Alexandra suffered from poor mental health. WikiArt.

9. It wasn’t just wealthy men who suffered from the glass delusion – one young princess was also hit by the mental illness

Again, the vast majority of cases of the glass delusion involved wealthy men. But it wasn’t a wholly male phenomenon. Women also suffered too, as the case of Princess Alexandra Amalie of Bavaria shows. Born in 1826, Princess Alexandra was the fifth daughter of King Ludwig I of Bavaria. She was a great beauty and should have had her pick of dashing princes. However, from an early age, Alexandra struggled with mental illness. She suffered a number of afflictions, including one of the most curious cases of the glass delusion ever recorded.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
The young Bavarian royal believed she had a glass piano inside her. Wikimedia Commons.

8. Princess Alexandra believed that if she fell, a glass piano inside her would shatter

When she reached her 20s, Princess Alexandra became fixated on the idea that, as a child, she had swallowed a grand piano made entirely of glass. However much her father the King or his physicians tried to persuade her otherwise, she was convinced that this glass piano remained inside her and was terrified that it could shatter at any moment. To stay safe, Alexandra became something of a recluse, devoting herself to her literary endeavors. She died at the age of 49 having never overcome her unique glass delusion.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
It is said the great Russian composer was terrified his head would fall off. Wikimedia Commons.

7. Was the great composer Tchaikovsky another sufferer of the glass delusion? The evidence suggests he was

Another notable figure who suffered – or is said to have suffered – from a variation of the glass delusion was the composer Peter Ilyich Tchaikovsky. According to several accounts, most of which have surely been exaggerated over the years, the Russian was convinced that his body was extremely fragile, and might even be made from glass. Above all, Tchaikovsky worried that his head would fall off if he did not hold onto his chin. Of course, this made conducting an orchestra extremely problematic, and it’s said he had to work hard to finally overcome his deep-seated fears and pick up the baton.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
The dawn of the Enlightenment brought the end of the glass delusion. Or did it? HistoryCrunch.

6. After peaking in the 16th century, the glass delusion steadily vanished, coinciding with the rise of science as a true academic discipline

After the famous cases of Princess Alexandra of Bavaria and the legendary Russian composer Tchaikovsky, instances of people suffering from glass delusion disappear from the history books. According to some scholars, the end of the delusion coincided with the rise of science as a proper academic discipline. Glass was no longer a wondrous substance, and neither was the human body a complete mystery. So, just as the Enlightenment brought an end to many of the more bizarre superstitious beliefs held by the peoples of Europe, so too did the dawn of the scientific age herald the end of the glass delusion.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
At the start of the industrial age, some people believed they were made from cement. CIS.

5. After the glass delusion came the ‘cement delusion’, when people thought they were made of the new and wondrous construction material

Interestingly, the belief that the glass delusion was caused by a fear of the unknown – in this case when glass was new and seen as wondrous or even magical – is lent further weight by the rise of the “cement delusion” of the 19th century. Again, cement was a new material, being used everywhere for construction. Physicians in London and across Europe recorded instances of patients believing their limbs were made from cement! And, once again, these soon disappeared when cement was no longer so new and mysterious.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Cases of the glass delusion have been found in medical notes from the 20th century. WBEZ.

4. Research has found that the glass delusion perhaps didn’t die out in the 19th century after all…

But has the glass delusion gone for good? Perhaps not. Research carried out in the Netherlands has found that, while it went out of fashion, there were still some cases of glass delusion well after the 1830s. According to Professor Ady Lameijin, former director of the Endegeest Psychiatric Hospital in the Dutch city of Leiden, his predecessors were treating people for the condition well into the 20th century. Most intriguing is a case dating from the 1930s – a full century after it’s widely acknowledged the glass delusion vanished for good.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
How many European asylums housed patients with glass delusions into the 20th century? Wikimedia Commons.

3. One class case of glass delusion occurred in 1930s Holland, and this time it involved a normal woman instead of a mad king

According to the old case notes from the 1930s, the woman was treated at the Leiden institution after telling her doctor that she felt her legs were made of glass. She also thought her back was made from glass. She hated people touching her and was becoming increasingly reclusive. At least this case has a happy ending. Professor Lameijin’s research found that she made a full recovery. Evidently, psychiatric treatment in 1930s Netherlands was far better than it was in the 16th century.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
Would Princess Alexandra have a different kind of delusion if she lived today? Wikimedia Commons.

2. Reports of people suffering from the glass delusion have been found as recently as the 1960s

The most recent recorded case of glass delusion dates back to 1964. Again, it was uncovered by Professor Lameijin. Indeed, it was he who personally treated the patient. A young man showed the classic signs of suffering from a full-on glass delusion. Not only did he feel fragile, he also felt transparent. Speaking to the BBC, Lameijin revealed that the patient was using the delusion as a coping mechanism to keep his overbearing family at bay. With careful psychiatric help, he was able to make a full recovery.

Nobles Used to Suffer from “The Glass Delusion” and Were Terrified of Breaking
King Charles VI made the glass delusion famous, but scholars are still trying to really understand it. JSTOR.

1. Could the glass delusion – or something like it – be set for a comeback

Despite being one of the strangest episodes of 16th century European history, relatively little research has been done into quite what caused the glass delusion. Was it simple superstition? Were royals and other powerful men scared of the rising mob? Or were they scared of glass, a wondrous invention back then? Nobody can say for sure. However, according to some psychiatrists, the modern world could see an outbreak of a similar delusion. As one 2015 article in the respected Paris Review noted: “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.”


Where did we find this stuff? Here are our sources

“The Glass Delusion”, Eleanor Morgan, The Grant Museum of Zoology, UCL, December 2014.

“An odd kind of melancholy: reflections on the glass delusion in Europe.” Gill Speak, The History of Psychiatry, 1990.

“The Delusion That Made Nobles Think Their Bodies Were Made of Glass” Hadley Mears,, December 2017.

“The ‘Glass Delusion’ Was The Most Popular Madness Of The Middle Ages.” Gizmodo, September 2014.

“The people who think they are made of glass.” BBC News, May 2015.

“Glass Delusions – Once a Common Form of Madness.” The Paris Review, May 2015.