After King Charles V of France died in 1380, his 11-year-old son Charles VI was next in line to inherit the throne. However, for the next 8 years it would be his uncles who ruled in his stead, spending money from the royal treasury and extorting heavy taxes from the common people. Overthrowing these avaricious regents and replacing them with highly competent advisors earned young Charles VI the title of ‘the Beloved’.

Just a few years later, this title would be replaced by one not so kind: ‘le fou’ or ‘the mad’. In 1392, Charles had what was thought to be the first psychotic episode of many. During a military expedition he became paranoid, and when a servant accidently dropped a lance, Charles turned around and began attacking his own knights, some of whom died.

In another episode Charles came to believe that he was made of glass – the glass delusion, which would occur intermittently throughout his life. Pope Pius II noted that Charles even had iron rods sewn into his clothes as reinforcement to stop him from breaking.

Although perhaps the most famous person to suffer from the glass delusion, Charles was by no means the only one – in the 15th to 16th centuries it was not uncommon for such delusions to be reported. Case numbers dropped after this period, and cases of the glass delusion are now rare.

Why do people have the glass delusion? In 1393, author Giovanni Boccaccio wrote: ‘We are all glass men, subjected to innumerable dangers. The slightest touch would break us, and we would return to nothing’.

Glass can be considered to have a number of meanings, which may aid us in analysis. At the time, glass was considered precious and almost untouchable, yet liable to shatter at the slightest jolt. The sufferers of this delusion in their ‘melancholia’ rejected the touch of other people, as the influence of others could easily cause them to shatter. Glass is also transparent, and this adds another dimension – that of the person who is both seen and unseen, someone who wants to hide from society. Perhaps the most significant factor was that in the 15th century glass was a new material and therefore more likely to become the subject of delusions. This would explain why cases started to decrease, and is analogous to cement delusions when cement was first discovered and more modern delusions about technology. In some ways, one could say that the content of delusions reflects contemporary culture.