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The Glass Delusion of Early Modern Europe

Who were the Glass Men and what caused their fears?

Illustration by Vincent Tsui
Source: Illustration by Vincent Tsui

Blondie taught us about the dangers of having a heart of glass, but for some people, that wasn’t a metaphorical problem. King Charles VI of France (1368-1422) literally believed he was made of glass. He wore reinforced clothing to protect his fragile body, and he refused to let courtiers come near in case they accidentally shattered him.

He wasn’t alone. Well-known public figures like the Dutch polymath Caspar Barlaeus suffered from a series of glass-related breakdowns, and physicians, playwrights, and writers like Miguel de Cervantes filled books with these so-called “Glass Men.”

The “glass delusion” was a regularly recorded condition in early modern Europe, especially between the fifteenth and seventeenth centuries. Fears of broken buttocks, shattered arms, and fragile heads were so common that the delusion almost seemed like an epidemic.

What made this condition so prevalent, and why, after centuries in the public eye, did it mostly disappear?

The Glass Delusion

In 1621, the English scholar Robert Burton published The Anatomy of Melancholy, a masterwork dedicated to low moods and their related illnesses. According to Burton, the glass delusion was one way in which melancholy-induced fear manifested. Melancholics frequently experienced paranoia, believed in imminent danger, and kept people at a distance out of disgrace and terror.

During the early modern period, the predominant model of the body placed great importance on melancholy. It was closely tied to black bile, one of the four fluids essential to health (a.k.a., “humors,” a term derived from the Latin word for “moist”).

Black bile was thick and sludgy, so if your body produced it in excess, you would feel sluggish, heavy, and sad. When heated, black bile took on a glassy sheen, which might partially explain its connection to this particular delusion.

Black bile was also the humor most commonly associated with the intellect, and medical knowledge at the time held that many scholars, poets, and philosophers tended toward a melancholic disposition. Well into the eighteenth century, physicians claimed that over-use of the mind and under-use of the body led to poor physical and mental health.

Therefore, the glass delusion was rooted in melancholy, and more specifically, in the single-minded devotion to intellectual pursuits. That explained why it was prevalent among wealthy, educated men.

But there’s more to the story. We still have to consider: why glass?

The Power of Glass

In the sixteenth and seventeenth century, few things were more prized than glass. After the Venetians discovered the art of making clear, colorless glass in the fifteenth century, wealthy individuals across Europe went ga-ga for it. Mirrors were soon born, and in the quest to create King Louis XIV’s fabled Hall of Mirrors, ministers engaged in espionage, kidnapping, and even murder to secure the trade secrets of the finest glassmakers.

It was so precious that glass was frequently treated as a mystical or alchemical object. Even sand and dirt could become a delicate, transparent substance through the skillful application of fire. Glass represented the transformation of something base to something wondrous.

Likewise, the Glass Men saw themselves as “a fragile container housing something ineffable and fundamental to being.” They were vessels of intellect and life, which had been destroyed and remade by a purifying fire. Indeed, some Glass Men also suffered from fire-related fears, worrying that they would melt.

In the early modern period, glass wasn’t just a fragile substance. It was valuable. Coveted. Powerful. By turning into glass, these fine men were literally becoming fine objects. Their melancholy made them delicate — and priceless.

The Vectors of a Transient Illness

Ian Hacking has studied “transient mental illnesses,” which appear in specific places and times and later fade away. As with the Glass Men, these illnesses are often prevalent among certain social classes or genders.

Hacking suggests that these kinds of conditions thrive in environments where four main vectors coincide. One vector is medical: the disease must fit within existing medical models. In the case of Glass Men, the existing framework of humors and melancholy accommodated the illness.

Cultural polarity is the second vector—the illness must fall between two opposing elements of contemporary culture. For example, the gentleman scholar was a respected, virtuous figure of the early modern period, but taken to excess, his virtues became pathological. His intellect became his undoing.

A third vector requires that the disease is observable. The popularity and prevalence of Glass Men cases put the illness in the public spotlight. Doctors warned their patients about excess, scholars dutifully studied the men afflicted with the condition, and broad audiences laughed at plays featuring “foolish” and tragic Glass Men.

Hacking’s final vector requires that “the illness, despite the pain it produces, should provide some release that is not available elsewhere in the culture in which it thrives.” Arguably, the glass delusion allowed prominent men to accomplish two goals simultaneously: 1) display their education and wealth, since this was a condition that afflicted gentleman scholars, and 2) free themselves from the rigid norms of social propriety and etiquette.

That’s not to say that the men afflicted by the glass delusion were conscious of these vectors. By all accounts, these men suffered terribly with their conditions, and tragically, some even committed suicide. What Hacking shows, though, is that social, cultural, and medical pressures can, at certain moments, create an environment just right for a particular illness to flourish.

When those conditions subside, so does the illness in question.


Burton, Richard. The Anatomy of Melancholy. (1621)

DeJean, Joan. The Essence of Style: How the French Invented High Fashion, Fine Food, Chic Cafés, Style, Sophistication, and Glamour. New York: Fress Press, 2005.

Gallant, James. “Disorders of Literary Men: An Approximate Synopsis of the 1825 Work by Chandler Robbins, MD.” Raritan 38, no. 4 (Spring 2019): 32-39.…

Hacking, Ian. Mad Travelers: Reflections on the Reality of Transient Mental Illnesses. Cambridge: Harvard University Press, 1998.

“The People Who Think They Are Made of Glass.” BBC Magazine. May 8, 2015.

Soth, Amelia. “The French King Who Believed He Was Made of Glass.” JSTOR Daily, March 29, 2018.

Speak, Gill. “’El licenciado Vidriera’ and the Glass Men of Early Modern Europe.” Modern Language Review 85, no. 4 (October 1990): 850-865.

Tissot, Samuel. De la santé des gens de lettres. (1768)

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