Fake news in the Middle Ages: 10 legends that stand the test of time

Before dark web conspiracy theories, people had the tavern. Information in the Middle Ages traveled slowly, mutating with every retelling. What we now call urban legends back then were terrifying theological myths that thousands accepted as facts. Discover ten of the most famous medieval legends that shaped the worldview of Europe for centuries.

In the mid-13th century, there was a rumor that a woman had successfully disguised herself as a man, climbed the ranks of the Catholic Church, and reigned as Pope for several years in the 9th century.

According to the legend, John Anglicus was in fact an exceptionally brilliant English woman who mastered theology. Her secret was supposedly uncovered during a papal procession through Rome, when she went into sudden labor and gave birth right in the middle of the street. While modern historians believe the story is just satire or folklore, it was widely accepted as historical truth during the late Middle Ages.

The urban legend of a noble outlaw who outsmarted the corrupt sheriff of Nottingham and stole from the rich to give to the poor began circulating in oral ballads around the 14th century.

Modern audiences know him as a cheerful hero in green tights, but early medieval versions of Robin were much grittier, violent, and anti-clerical. Historians have spent centuries looking through court records trying to find a definitive Robin Hood. Most conclude he was a complex figure, the medieval manifestation of rebellion against an unfair system.

Originating in the late 12th century through the French romances of Chrétien de Troyes, the Grail was described as the sacred chalice used by Jesus Christ at the Last Supper, and later used to collect his blood during the Crucifixion.

The legend claimed that this vessel possessed miraculous healing powers, granted eternal youth, and provided infinite food. It became an obsession across Western Europe. Knights and nobles genuinely believed the Grail was hidden somewhere in a secluded castle, waiting for a perfectly pure warrior to find it.

Did a heroic king once rule Britain from a golden castle called Camelot, surrounded by a Round Table of knights? The legend of Arthur was popularized in the 1130s by Geoffrey of Monmouth’s History of the Kings of Britain, a mixture of vague fragments of real 5th-century Celtic warlords and doses of pure fiction.

Arthur became the gold standard for medieval chivalry. The urban legend expanded to include his magical sword Excalibur, the wizard Merlin, and the tragic betrayal by his queen, Guinevere. The myth was so powerful that English monarchs, including Edward I, used Arthurian imagery to legitimize their rule, even claiming to have discovered Arthur’s tomb at Glastonbury Abbey in 1191.

The idea of a magical spring capable of reversing aging and curing all sickness is an ancient one, but it became a dominant urban legend during the Middle Ages. The myth was blown up by the Alexander Romance, a fictionalized collection of stories about Alexander the Great that circulated in Europe at the time.

According to these tales, Alexander and his armies searched for the "Water of Life" on the outer edges of the known world. Medieval travelers and mapmakers speculated that this fountain existed somewhere in India or the mythical lands of the East. This legend laid the groundwork that, centuries later, would drive Spanish explorers like Juan Ponce de León to hunt for it in the Americas.

Medieval life was deeply preoccupied with sin, demonic temptation, and the supernatural. When people experienced terrifying nightmares or sleep paralysis, they didn’t have modern psychology to explain it. Instead, they blamed the incubus and succubus.

An incubus was a male demon believed to prey upon sleeping women, while a succubus was a female demon that seduced men. These entities weren’t just folklore, they appeared in serious medieval theological texts. Church scholars even argued about how these demons operated, warning that they could steal human material to create monstrous offspring.

Following the Assyrian conquest of the Kingdom of Israel in the 8th century BCE, ten of the twelve Jewish tribes vanished from the biblical narrative. In the Middle Ages, this historical mystery became a geopolitical urban legend.

European Christians and Jews alike shared the thought that the Ten Lost Tribes were living out past the edges of the mapped world. They were said to be trapped behind the mythical Sambation River, a river made of stones and sand that only stopped flowing on the Sabbath. A major component of this legend was the fear or hope that these millions of hidden warriors would one day cross the river.

The Wandering Jew is one of the most tragic urban legends of the time, first appearing in written European chronicles around the 13th century. The story goes that a Jewish shoemaker or guardsman named Cartaphilus (or Ahasuerus in later versions) taunted Jesus as he carried his cross to Calvary, telling him to hurry up. Jesus supposedly replied: "I am going, but you will wait until I return."

As a result, the man was cursed with immortality and doomed to walk the earth without rest until the Second Coming of Christ. Throughout the Middle Ages, people across Europe claimed to have met this sorrowful traveler, describing him as a knowledgeable man who spoke every language.

In the year 1212, a wave of religious hysteria swept through France and Germany. The resulting story became one of the most heartbreaking urban legends of the era: the Children’s Crusade. The popular tale stated that thousands of unarmed children, inspired by visions, marched toward the Mediterranean Sea, believing the waters would part for them so they could peacefully reclaim Jerusalem. When the sea failed to part, corrupt merchants supposedly loaded them onto ships and sold them into slavery in North Africa.

Beginning in the mid-12th century, rumors spread of Prester John, a wealthy Christian king who ruled a utopian empire somewhere in the heart of Asia or Africa.

The legend reached a peak when a forged letter, supposedly written by Prester John himself, circulated among European monarchs. The letter described a kingdom with rivers filled with gold, the Fountain of Youth, and a mirror through which the king could see his entire empire. During the Crusades, European armies hoped that Prester John’s legions would march from the East to save them.

Mind games

The scruffy barber and the swift tortoise—does reality even make sense?

Image: 愚木混株 cdd20

Some ideas challenge what we think we know—paradoxes twist logic until reason bends or breaks. These classic thought experiments, from ancient puzzles to modern contradictions, expose gaps in philosophy, math, time, and perception. Here are 10 paradoxes that’ll warp your mind and leave you questioning reality.

Image: Josh Sorenson

If a barber shaves everyone who does not shave themselves, who shaves the barber? If he shaves himself, he must not; if he doesn’t, he must.

This self-referential paradox, posed by Bertrand Russell in 1918, demonstrates a fundamental problem in set theory. It inspired Russell's theory of types, which aimed to avoid such contradictions in formal logic and mathematics. Perhaps the barber will simply choose to grow a beard.

Image: Joshua Hoehne

The statement "This sentence is false" cannot be true or false. If true, then it’s false; if false, then it’s true.

Known since ancient Greece as the Epimenides paradox, it underpins challenges in many logical systems. Although it seems simple at first, deeper thought reveals there is no resolution. Many have tried to solve or circumvent it, yet it remains unsolved.

Image: Zoltan Tasi

If you replace every part of a ship, is it still the same ship? What if you reassemble the old parts into a second ship?

This metaphysical problem dates back to Plutarch. It challenges identity and continuity, and has many analogs in biology (e.g., human cells constantly replacing themselves) and even AI (replicated minds in machines).

Image: Luca Ambrosi

Achilles and a tortoise race each other. As a courtesy, Achilles gives the tortoise a head start. However, Zeno argues Achilles can never catch it, because he must first reach where the tortoise was before, infinitely.

Although this paradox seems crazy and absurd—in real life, obviously Achilles would win the race—what Zeno is pointing to are the infinite gaps between finite numbers. The absurd argument, being that all motion is impossible due to infinite division, helps illustrate the limits of mathematical models of the world.

Image: Gianluca Carenza

If you went back in time and killed your grandfather before your parent was born, how could you exist to do it in the first place?

This classic time travel paradox highlights the problems with causal loops. Theoretical physics offers some resolutions, such as branching timelines (as in the "many-worlds interpretation") or even stranger concepts like "closed time-like curves"—but its true resolution is still debated today.

Image: Caryn Sandoval

The unexpected hanging paradox involves a judge sentencing a prisoner to be hanged on an unknown day of the following week, but the execution must be a surprise. The prisoner logically deduces he cannot be hanged on the last day, nor the day before, and so on, concluding he will not be hanged at all. The next week, to the prisoner’s surprise, the executioner knocks on the prisoner's door at noon on Wednesday.

The unexpected hanging paradox, also known as the surprise test paradox, concerns a person’s expectations about the timing of a future event they are told will occur unexpectedly. It poses a problem in epistemic logic—our knowledge about what we know—and has no widely accepted resolution.

Image: Max Muselmann

A time traveler brings a copy of Shakespeare’s Hamlet to the past before Shakespeare wrote it. Who actually authored it?

This paradox suggests that time travel allows the emergence of information or objects with no discernible origin. It is a common trope in science fiction and defies causality, sparking heated debates in temporal logic.

Image: Maximus Meadowcroft

Can an all-powerful being create a stone so heavy that it cannot lift it?

This simple question highlights one of the main paradoxes behind the concept of omnipotence. Some resolve it by limiting omnipotence to what is logically possible; others reframe omnipotence as maximal power rather than the ability to create contradictions.

Image: Sarah Doffman

Removing one grain of sand doesn’t make a heap cease to be a heap. So, when does it stop being a heap?

This problem highlights the issue of vague definitions. At its core, it challenges not logic itself, but our use of language and the way we categorize concepts.

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A hotel with infinite rooms is full, but can still accommodate new guests by shifting each one to the next room.

This paradox, created by David Hilbert, illustrates the strange properties of infinite sets—whether rooms or any infinite collection of objects. It is used in set theory to demonstrate how infinities can behave in non-intuitive ways.