Bust of a bearded man in a ruff and cap made of clear glass with a fine crack, against a light grey background

DESCRIPTION: Glass delusion was the belief that one was made of glass and could shatter. Recorded cases, the theory of melancholia, Cervantes, Descartes and what the sources reveal from a psychiatric perspective.

Delusion of being made of glass: the history of a delusion and its psychiatric interpretation

Between the 15th and 17th centuries, chroniclers, doctors and poets reported on people who were convinced that they were made of glass. The best-known case is that of King Charles VI of France. The medical community of the time attributed glass delusion to melancholia; Cervantes turned it into a novella, whilst Descartes cited it as an example of madness. What can be said about those affected based on these sources depends on the nature of the source in question.

Glass delusion: clinical presentation and the evidence

The accounts follow a recurring pattern. Those affected believe their body, or part of it, to be made of glass: the head, the legs, the buttocks, sometimes the entire body. Some believe themselves to be a glass vessel. Their behaviour stems from this conviction. They avoid being touched, pad their clothing and seating, refuse to sit down or will only sit on soft surfaces, and demand that others keep their distance.

Gill Speak compiled the historical record in 1990, covering the years 1440 to 1680. Three types of source are included. Chronicles and letters report on individual cases, often second-hand and decades later. Medical textbooks collect examples to illustrate a disease theory. Literary and philosophical texts use the ‘glass man’ as a character or as an argument. But even if one adds up these three categories, one does not obtain any case statistics. It is impossible to estimate from the sources how many people were actually affected.

Charles VI and Caspar Barlaeus: two documented cases

Charles VI (1368–1422) fell ill in 1392 whilst on a military campaign against Brittany. Near Le Mans, he attacked his own companions and killed several of them. Further episodes followed right up until his death. In the course of his illness, the ‘glass delusion’ was just one episode amongst many.

The source for this account is Enea Silvio Piccolomini, later Pope Pius II (1405–1464), in the sixth book of his *Commentarii*. Piccolomini names the illness explicitly. During the campaign, the king was suddenly seized by the illness, ‘quem vocant mania’, which is called mania. He spoke foolishly, attempted even more foolish things and gave no sensible answers to questions. In Paris, his condition worsened day by day. Then comes the sentence on which all later accounts are based: ‘Existimabat nonnunquam se vitreum esse’. At times he believed himself to be made of glass, would not allow himself to be touched, had iron rods sewn into his clothing, and took various measures to protect himself so as not to shatter should he fall.

Piccolomini continues: the king had moments of lucidity, ‘dilucida intervalla’. When he came to his senses, he is said to have been ashamed of his earlier behaviour and therefore sought solitude. There is no mention of melancholy at this point. Piccolomini wrote decades after the events and was not an eyewitness. His account is nevertheless the oldest source concerning the king’s delusion of being made of glass. Later embellishments, such as the claim that Charles wrapped himself in blankets, do not appear in his account.

Caspar Barlaeus (1584–1648), poet, humanist and professor at the Athenaeum Illustre in Amsterdam, which opened in 1632, suffered repeatedly from severe melancholic crises. His letters were edited by F. F. Blok in 1976. In the secondary literature, he is attributed with ‘glass mania’. Speak considers this attribution to be unsubstantiated, as it is based solely on a speech from 1635 in which Barlaeus describes the ‘glass man’ as a symptom of melancholia: a person who believes himself to be made of glass and, full of fear, recoils from anyone who comes near him. Barlaeus’s case illustrates how a melancholic scholar can be portrayed as a ‘glass man’ in the literary tradition. His contemporary Constantijn Huygens mocked the ‘glass man’ delusion in 1622 in his satire ’t Costelick Mal. The motif was therefore well known in these circles.

Melancholy and scholarship in Ficino and Burton

The theory of the humours provides the interpretative framework. Marsilio Ficino devotes the first book of *De vita libri tres* (1489) to the health of scholars. According to Ficino, study, working at night and the influence of Saturn cause black bile to predominate, and those who think a great deal become melancholic.

Robert Burton takes up this idea in 1621 in *The Anatomy of Melancholy*. He devotes a separate section to excessive study as a cause of melancholy. Among the psychological symptoms, he lists the melancholic’s fear of being made entirely of glass and therefore of not letting anyone get close to them. He places this ‘glass delusion’ amongst a range of fears, and elsewhere Burton attributes to this fear itself the power to dominate the imagination.

These texts provide evidence for a contemporary theory. They link glass mania with melancholy, and melancholy with the life of a scholar. The fact that the recorded cases are concentrated amongst the educated and the nobility stems in part from this theory itself. Doctors sought out melancholy where scholarship led them to expect it. The educated read the same books and described their suffering in the terms found therein. And those who could not write and had no personal physician left no medical records behind.

Du Laurens and the collection of medical case studies

André du Laurens (1558–1609), Chancellor of the Faculty of Medicine at Montpellier and personal physician to Henry IV, published a *Discours des maladies mélancoliques* in 1597. In it, he explains melancholy as arising from the coldness and dryness of black bile and describes various cases. One such case is that of a ‘glass man’ who was wasting away on a bed of straw so as not to shatter. According to du Laurens, a fire quickly brought him back to his senses.

For the medical community of the time, this ‘glass man’ delusion thus served as a case study: an absurd conviction that could be dispelled by a sudden fright. Du Laurens’s treatise was translated and reprinted many times, and later authors, including Burton, drew upon it. Consequently, some of the 17th-century case reports repeat the same examples.

Cervantes’ Licenciado Vidriera: the ‘glass man’ as a literary figure

In the *Novelas ejemplares* of 1613, Miguel de Cervantes tells the story of Tomás Rodaja, a gifted student from Salamanca. A woman whose advances he had rejected gives him a love potion in a quince. Tomás survives and from then on believes himself to be made of glass. He demands that people speak to him from a distance and, in winter, sleeps buried up to his neck in straw.

He becomes famous as the ‘Glass Man’. He answers questions with scathing judgements on doctors, judges, actors and courtiers, and people flock to him. After his recovery, he returns under his real name and wishes to practise as a lawyer. No one listens to him any more. He goes to Flanders as a soldier and dies there.

Cervantes takes little interest in the illness itself. The delusion of being made of glass grants his character the freedom of a fool, and the novella is about how society listens to the madman but turns its back on the man who has been cured.

Descartes: Glass Men in Methodical Doubt

In the first of the *Meditations on First Philosophy* (1641), René Descartes asks whether he can doubt that he has a body and hands. He refers to madmen who believe themselves to be kings, even though they are poor, or who believe they are pumpkins or *ex vitro conflatos*, made of glass. Descartes immediately rejects the comparison, because he does not wish to model himself on such people, and moves on to the dream argument.

The ‘glass man’ is an example here that every reader is familiar with. Its function is philosophical: it marks the boundary beyond which methodological doubt is no longer considered reasonable. In 1961, Michel Foucault interpreted this passage as signifying the exclusion of madness from modern thought. Jacques Derrida contradicted him in 1963, interpreting the passage as an intermediate step in a more far-reaching doubt. The dispute shows how firmly the glass man was anchored in the imaginative world of the time. John Locke, too, cites him in 1690 in his *Essay Concerning Human Understanding* as an example of madness.

Why glass? Crystal glass, windows and lenses

The most common explanation points to the cultural history of the material. Around the middle of the 15th century, an almost colourless, clear glass known as ‘cristallo’ was successfully produced on Murano. In the 16th and 17th centuries, glass windows became widespread in middle-class homes; spectacles had been known since the late 13th century; and around 1609, Galileo and others turned the first telescopes towards the heavens. Glass was precious, transparent and fragile all at once.

These characteristics explain why glass was a suitable subject for delusions. Fragility aligns with anxiety; transparency with the fear of being seen through; and preciousness with the self-image of a learned or noble person. In the earliest case, however, this explanation does not hold water. Charles VI fell ill half a century before the ‘cristallo’. Even before Murano, glass was a luxury good and a symbol of fragility; yet the dating calls for caution regarding overly simplistic inferences drawn from the history of technology. The history of materials explains the form an illness might take, but leaves open the question of why a particular person fell ill.

What the descriptions reveal from a psychopathological perspective

The descriptions allow only a partial classification. They are insufficient for a diagnosis of Charles VI, Barlaeus or any other ‘glass man’, as details of the course of the illness, accompanying symptoms and the accounts of those affected regarding their own experiences are missing.

Firstly, this is a body-related delusion: an unshakeable conviction regarding the nature of one’s own body. Secondly, those affected consistently base their behaviour on this conviction. Anyone who has iron rods sewn into their clothing is certain of their cause. Thirdly, in many accounts the delusion is confined to a single theme, whilst the rest of their thinking remains intact. Fourthly, the accompanying emotion is anxiety, and contemporaries classified this presentation as melancholia.

This pattern corresponds to several modern categories. A circumscribed body delusion with an intact personality is consistent with a delusional disorder of the somatic type. A body delusion occurring within severe, anxiety-tinged depression is consistent with psychotic depression. Its closest relative is Cotard’s syndrome, which Jules Cotard described in 1880 as a delusion of negation within a severe, anxious form of melancholia. Those suffering from Cotard’s syndrome believe their body to be dead, empty or non-existent. The ‘glass man’ believes his body to be alive, but fragile and under threat. In the case of Charles VI, the source provides more detail than for the other cases: an acute onset whilst on a military campaign, disorganised speech and behaviour, recurrent episodes with lucid moments, and shame regarding one’s own behaviour once the episode has subsided. A phasic course with insight into the illness during remission is consistent with bipolar disorder. However, Piccolomini’s term ‘mania’ does not support this, as in the 15th century it referred to frenzy in any form. Even Charles’s case is insufficient for a diagnosis.

Coenaesthesia in Huber: a comparison

In 1957, Gerd Huber described a coenaesthetic form of schizophrenia in which abnormal bodily sensations are prominent: numbness and stiffness, pain, sensations of electric shocks and heat, feelings of abnormal heaviness or lightness, and the sensation that parts of the body are shrinking or expanding. Those affected experience these as distinct, alien sensations on or within the body.

A comparison suggests itself because Huber shows how an abnormal bodily sensation can give rise to a delusional interpretation. A sensation of stiffness or numbness, interpreted within the imaginative world of the Renaissance, could lead to the conviction that one is made of glass. The accounts of ‘glass people’ describe conviction and action; sensations are scarcely mentioned in them. Whether a bodily sensation was the starting point cannot be deduced from the sources. The comparison describes a possible mode of origin and does not claim any historical continuity between the ‘glass people’ and Huber’s patients.

Decline and later cases

After the 17th century, reports became less frequent. Isolated cases of ‘glass people’ still emerged in the 19th and 20th centuries, such as one reported by the Hispanist Raymond Foulché-Delbosc from a Parisian institution. Speak found only two such cases in the modern era, both of which remain unconfirmed.

There are two possible explanations for this decline. It may be that fewer people suffered from this particular delusion because other materials and techniques took the place of glass, which had previously been regarded as exotic. Patients in the 19th and 20th centuries spoke of electricity, apparatus and rays. It is also possible that the category under which such cases were classified simply ceased to exist. With the decline of humoural theory, the old concept of melancholy crumbled, and a 19th-century ‘glass man’ ended up in a different category. What is certain is that the content of delusions follows the prevailing ideas of their time. Glass delusion is the clearest historical example of this.

Key points in brief

• Glass delusion is the belief that one consists wholly or partly of glass. It is primarily documented from the 15th to the 17th centuries.

• The sources include chronicles and letters, medical textbooks, and literary and philosophical texts. They provide varied accounts and do not yield any case statistics.

• Charles VI’s glass delusion is recorded in the sixth book of Pius II’s *Commentarii*. Piccolomini refers to the condition as *mania* and describes lucid intervals. Caspar Barlaeus’s glass delusion is unsubstantiated.

• Ficino, du Laurens and Burton attributed the ‘glass mania’ to melancholia and melancholia to a life of scholarship. The prevalence amongst the educated is partly attributable to this theory.

• Cervantes uses the ‘glass man’ as a figure of the fool, whilst Descartes employs him as a borderline case of doubt.

• From a psychopathological perspective, the sources describe a circumscribed, anxiety-laden delusion concerning the body. They do not allow for specific diagnoses.

• Reports become less frequent after the 17th century. The content of the delusions reflects the prevailing ideas of their time.

Sources

· Speak, G. (1990): An odd kind of melancholy: reflections on the glass delusion in Europe (1440–1680). History of Psychiatry 1 (2), 191–206. https://doi.org/10.1177/0957154X9000100203

· Charles VI of France: the Glass King. Psychiatry in history. British Journal of Psychiatry. https://www.cambridge.org/core/journals/the-british-journal-of-psychiatry/article/charles-vi-of-france-the-glass-king-psychiatry-in-history/5E29BAD20220B0C7C2DEF6A0D3395A5D

· Sanderson, T.: Fear and Fragility. The Glass Delusion and Its History. The Public Domain Review. https://publicdomainreview.org/essay/fear-and-fragility-the-glass-delusion-and-its-history/

· Pius II (Enea Silvio Piccolomini): *Commentarii rerum memorabilium, quae temporibus suis contigerunt*. Rome 1584, Book VI, p. 272. https://archive.org/details/bub_gb_Ru1Ws-B7bqIC

· English: Memoirs of a Renaissance Pope. The Commentaries of Pius II, Books VI–IX, trans. by F. A. Gragg. Smith College Studies in History 35 (1951), p. 425.

· Speak, G. (1990): ‘El Licenciado Vidriera and the Glass Men of Early Modern Europe’. *The Modern Language Review* 85 (4), 850–865.

· Huygens, C. (1622): Satyra. Dat is ’t Costelick Mal. Middelburg. In: De Gedichten van Constantijn Huygens, ed. by J. A. Worp, vol. 1, Groningen 1892, p. 246, lines 103–108.

· Barlaeus, C. (1635): De animae humanae admirandis. In: Orationum liber, Amsterdam 1643, p. 111.

· Blok, F. F. (1976): Caspar Barlaeus. From the Correspondence of a Melancholic. Assen: Van Gorcum.

· Ficino, M. (1489): De vita libri tres.

· Du Laurens, A. (1597): Discours de la conservation de la vue, des maladies mélancoliques, des catarrhes et de la vieillesse. Paris. English 1599, facsimile Oxford 1938, p. 102.

· Burton, R. (1621): The Anatomy of Melancholy. Part 1, Section 2, Chapter 3, Subsections 5 (Fear as a Cause) and 15 (Excessive Study). Part 1, Section 3, Chapter 1, Subsection 2 (Symptoms of the Mind, Delusions of Opacity).

· Cervantes, M. de (1613): El licenciado Vidriera. In: Novelas ejemplares.

· Descartes, R. (1641): *Meditations on First Philosophy*, Meditation I.

· Locke, J. (1690): An Essay Concerning Human Understanding, Book II, Chapter 11, § 13.

· Cotard, J. (1880): On hypochondriacal delirium in a severe form of anxious melancholia. Annales médico-psychologiques.

· Huber, G. (1957): Coenaesthetic schizophrenia. Advances in Neurology, Psychiatry and Related Fields 25, 491–520.

· Foucault, M. (1961): A History of Madness in the Classical Age.

· Derrida, J. (1963): Cogito and the History of Madness. Reprinted in: Writing and Difference (1967).