If there is one thing we can say with confidence about medieval Europeans, it is that they were absolutely certain someone was out to get them. And not just any someone—an elaborately organized, diabolically clever, probably supernatural someone, working through networks so vast and secret that their very invisibility was proof of how powerful they must be.

In this respect, at least, we haven't changed much.

But medieval conspiracy theories had a quality that modern ones often lack: they were remarkably creative. Where we tend to blame shadowy government agencies or tech billionaires—rather unimaginative targets, really—the medieval mind could conjure networks involving demons, foreign sorcerers, poisoned spices, shape-shifting werewolves, and the occasional immortal monk. If you're going to be paranoid, you might as well be theatrical about it.

The Devil's Grand Alliance

To understand the medieval conspiracy mindset, you have to appreciate that for most people in, say, the fourteenth century, the Devil was not a metaphor. He was as real as the king, considerably more powerful, and much better organized. While earthly rulers squabbled over patches of territory and couldn't manage to collect taxes without starting a rebellion, Satan apparently ran a continent-spanning operation with the efficiency of a modern logistics company.

According to authorities like Johannes Nider, a fifteenth-century Dominican friar who really ought to have found better uses for his time, witches, heretics, and Jews were all working together in a single coordinated alliance with Satan himself. Their goal? Nothing less than the destruction of all Christian monarchies. How exactly a scattered collection of elderly village healers, theological dissenters, and marginalized religious minorities were supposed to accomplish this was never entirely clear, but that was rather the point. The conspiracy's very implausibility was evidence of dark supernatural backing.

The Cathars of southern France were particular targets of this thinking. Here was a group of Christians who believed, rather inconveniently for the Church, that the material world was the creation of an evil deity. They practiced vegetarianism, rejected the sacraments, and thought the cross was a symbol of torture rather than salvation—all of which suggested, to orthodox authorities, that they must be part of some underground anti-Church network coordinated directly by demons.

The Waldensians, another group of dissenters who had the radical notion that ordinary people should be able to read the Bible in their own language, were lumped into this same supposed conspiracy. Medieval authorities struggled to believe that separate groups might simply have arrived at similar conclusions independently. It had to be coordination. There had to be a network.

The Poisoners Among Us

If supernatural conspiracies were the domain of theologians and inquisitors, poison conspiracies belonged to everyone. And I do mean everyone. In medieval and Renaissance Europe, poison was the great universal explanation for anything bad that happened, particularly if it happened suddenly.

When the Black Death arrived in 1348, killing roughly a third of Europe's population, people were desperate to find someone to blame. The actual culprit—fleas on rats carrying the bacterium Yersinia pestis—would have seemed absurdly mundane even if anyone had thought of it. Instead, two groups bore the brunt of suspicion: lepers and Jews.

The theory went something like this: lepers, bribed by foreign enemies (sometimes the Muslim world, sometimes vaguely defined "Eastern powers"), were given packets of toxic powder to drop into public wells. The powder supposedly contained a mixture of human blood, urine, and herbs, which is both disgusting and—from a plague-transmission standpoint—entirely ineffective. But effectiveness wasn't really the point. The point was that someone, somewhere, had to be responsible.

Jewish communities faced even worse accusations. The "Synagogue of Satan" myth held that Jews across Europe were secretly coordinating against Christian kingdoms, receiving instructions through coded letters and possibly from demons. During plague years, this belief led to horrific massacres in hundreds of towns and cities. In Strasbourg alone, approximately two thousand Jews were burned alive in February 1349—months before the plague even reached the city.

This is the terrible thing about conspiracy theories: they don't require the conspirators to have actually done anything. The accusation itself becomes the evidence.

The Italian Method

If you wanted proper poisoning—the professional kind, where the victim actually died and the perpetrator actually benefited—you went to Italy. At least, that's what everyone north of the Alps believed.

The Medici family of Florence were said to maintain an entire network of poisoning resources: secret laboratories, disguised assassins, and court astrologers who could determine the most auspicious moment to murder someone. Whether any of this was true is almost beside the point. The Medici were rich, powerful, and politically ruthless. In the popular imagination, this had to mean poison.

Catherine de' Medici, who became Queen of France, inherited this reputation despite having limited evidence against her. Rumor held that she employed special perfumers who could craft lethal scents—perfumed gloves, poisoned pages of books, toxic bouquets. It was said you could die simply by smelling a gift from Catherine. This is, to be clear, not how poison works. But it's an excellent detail if you're writing court gossip, and Renaissance courtiers were nothing if not creative writers.

Venice's Council of Ten—the secretive committee that handled state security—had an even more terrifying reputation. Foreign observers believed the Council employed a vast network of spies in every European court, using methods that included (according to various accounts) poison, prostitutes, and "coded religious orders," whatever those might be. The Venetians, it should be noted, did absolutely nothing to discourage these rumors. Being feared was good for business.

The Scholars of Forbidden Things

The Renaissance is usually presented as a flowering of rationality and human potential—Michelangelo painting the Sistine Chapel, Leonardo designing flying machines, the general rediscovery of classical learning. What's often left out is that many of these same brilliant minds were also deeply invested in what we would now call the occult, and that their neighbors found this absolutely terrifying.

Scholars like Marsilio Ficino and Pico della Mirandola were interested in Hermetic philosophy—a tradition they believed dated back to ancient Egypt and contained secrets about the nature of reality, the manipulation of cosmic forces, and possibly the achievement of immortality. They saw themselves as recovering lost wisdom. Their critics saw a hidden brotherhood of sorcerers attempting to control European politics through magic.

Heinrich Cornelius Agrippa, a German polymath of the early sixteenth century, wrote extensively on natural philosophy, skepticism, and the treatment of women—but became famous primarily for his book on occult philosophy. Rumors spread that he maintained a demonic familiar disguised as a black dog and that he had established a school teaching students to hypnotize nobles using magical symbols. The school did not exist. The dog was just a dog. But the rumors persisted for centuries.

John Dee, mathematician and advisor to Elizabeth I, genuinely did claim to communicate with angels through a complex system involving crystal balls and an assistant who could see visions. But his actual conversations with these angels—recorded in exhaustive detail—were mostly concerned with obscure theological questions and the proper pronunciation of mystical words. This did not stop contemporaries from believing he ran an "angelic espionage" network that gathered intelligence across Europe through supernatural means. Elizabeth's government did use him as an intelligence asset on his travels abroad, but through rather more conventional methods.

The legend of Faust—the scholar who sold his soul to the Devil for knowledge and power—captured this anxiety perfectly. Universities like Wittenberg and Prague were rumored to harbor entire cabals of scholars who had entered similar pacts, trading their eternal souls for earthly influence. Young men sent off to study theology might come back as servants of darkness. From a parent's perspective, this was rather more dramatic than worrying about excessive drinking and poor study habits, but perhaps no less anxiety-inducing.

The Problem with Princes

Royal courts generated conspiracy theories the way modern social media generates outrage: constantly, prolifically, and with minimal concern for evidence. Part of this was structural. Medieval and Renaissance succession was genuinely messy—kings died young, claimed heirs disappeared, pretenders emerged from nowhere claiming to be long-lost princes. In this environment, every explanation was a conspiracy theory.

Take the Princes in the Tower—the young Edward V of England and his brother Richard, who vanished from the Tower of London in 1483 after their uncle took the throne as Richard III. They almost certainly died there, probably murdered. But rumors persisted for decades that one or both had escaped. Multiple pretenders appeared claiming to be the younger prince, Richard of Shrewsbury, including one who managed to gain support from several European monarchs before being captured and executed.

Portugal experienced something similar with King Sebastian I, who disappeared during a disastrous military campaign in Morocco in 1578. His body was never definitively identified. For the next sixty years, pretenders appeared claiming to be Sebastian, returned to reclaim his throne. The belief that the king was still alive—that he would return to restore Portuguese independence—became known as "Sebastianism" and persisted in various forms for centuries. Hope, it turns out, is remarkably resistant to evidence.

Joan of Arc, the French peasant girl who led armies and was burned for heresy in 1431, generated her own conspiracy theory: that the English had actually burned a double while the real Joan escaped. A woman claiming to be her appeared several years later and was initially accepted by Joan's own brothers. Whether they genuinely believed her or simply found it useful to have a famous sister again is one of those questions history cannot answer.

The She-Wolves and Witch-Queens

Powerful women in the medieval period faced a particular form of conspiracy thinking: if they exercised influence, it must be through illegitimate means. Usually this meant witchcraft, seduction, or both.

Queen Isabella of France, who helped depose her husband Edward II in the 1320s, was nicknamed "the She-Wolf." Her political success was attributed to sorcery and foreign agents rather than to the rather obvious factors of her husband's disastrous rule, his extremely unpopular favorites, and Isabella's genuine political skill. A woman couldn't simply be capable; she had to have supernatural help.

Anne Boleyn, Henry VIII's second wife, faced similar accusations. When Henry's passion for her cooled and he needed grounds for her execution, charges of witchcraft proved convenient. She had allegedly used sorcery to seduce the king—which raised the interesting question of why, if she had such powers, she hadn't used them to produce the male heir Henry desperately wanted. But consistency was never the point.

Mary, Queen of Scots, Catholic claimant to the English throne, was believed to lead a covert network planning to assassinate Elizabeth I. In this case, there was actually something to the accusations—various Catholic conspiracies did form around Mary's claim—but the conspiracy thinking went far beyond the evidence, imagining vast international networks where often there were only small groups of desperate men with poorly conceived plans.

The Suspicious Stranger

The conspiracies we've discussed so far involved popes, princes, and sorcerers. But ordinary people had their own versions, tailored to local anxieties.

Traveling peoples—the Romani, itinerant beggars, wandering merchants—were widely suspected of operating secret intelligence networks. The belief held that they communicated through hand signals, concealed tattoos, and coded folk songs, passing information between towns and perhaps serving foreign masters. This justified all manner of harsh legislation against nomadic populations. The "evidence" for these networks was entirely circular: their movements seemed suspicious because authorities already believed them to be conspirators.

Barber-surgeons, who performed medical procedures along with haircuts and shaves, faced accusations of running a murder guild. They were said to deliberately bleed patients to death, then sell the corpses to alchemists seeking raw materials. It's easy to see how this belief arose: barber-surgeons worked with blood, their treatments often failed (medieval medicine being what it was), and they did sometimes provide bodies for anatomical study. The conspiracy made a kind of terrible sense if you didn't know how disease actually worked.

Even relatively mundane trades fell under suspicion. Italian spice merchants were believed by some northern Europeans to be deliberately poisoning Christian populations through saffron, pepper, and sugar. The German clockmakers' guilds were rumored to possess occult knowledge about time itself, manipulating fate and seasons through their mysterious mechanisms. Weavers were accused of stitching coded messages into tapestries for foreign spies.

What's striking about these beliefs is how they combined legitimate anxieties—foreigners with unclear loyalties, practitioners wielding specialized knowledge—with fantastical elaborations that transformed everyday workers into agents of darkness. The medieval mind didn't distinguish sharply between natural and supernatural explanations. A clockmaker might just be very good at his craft. Or he might be manipulating the fabric of time. Both seemed possible.

The Books That Shouldn't Exist

Medieval conspiracy theories often centered on forbidden knowledge—texts that supposedly granted terrible powers to those who possessed them.

The "Grimoire of Pope Honorius" was believed to be a papal book that taught priests to command demons. The fact that no copy could be produced—that the book's existence was attested only by rumor and accusation—only enhanced its mystique. If you could find it, you'd have power over the forces of Hell. Various texts claiming to be this grimoire circulated in later centuries, but the original remained tantalizingly out of reach.

The "Egyptian Book of Thoth" was another supposed text of power—an ancient Egyptian manual granting control over spirits, immortality, and dominion over princes. Renaissance occultists were believed to pass it secretly from master to apprentice, forming an invisible chain of initiated sorcerers stretching back to the pharaohs. The Hermetic texts that scholars like Ficino actually studied were considerably less dramatic, dealing mainly with philosophical cosmology, but rumor improved on reality.

Even the Cathars were believed to possess a sacred relic or book capable of bringing down the Church—hidden when their last fortress fell, waiting to be discovered by the right (or wrong) seeker. The treasure of Montségur has inspired treasure hunters and conspiracy theorists ever since, despite no evidence that anything more valuable than ordinary Cathar believers was present when the fortress surrendered.

Dante's Divine Comedy was interpreted by some readers as containing coded predictions, blueprints for revolutions, and hidden attacks on powerful families. Secret societies supposedly used the text as a guide, extracting meaning that ordinary readers missed. This tradition of finding hidden messages in literature has never really stopped—it just moved on to other texts, from Shakespeare to The Da Vinci Code.

Written in Stone

Cathedral architecture proved irresistible to conspiracy theorists. The great Gothic churches rising across Europe were expensive, technically demanding, and decorated with imagery that required expertise to interpret. This combination—specialized knowledge, vast resources, mysterious symbols—practically begged for conspiratorial interpretation.

Stonemasons, it was believed, had embedded secret teachings in their work: in the patterns of labyrinths, in the arrangement of gargoyles, in the geometry of rose windows. The teachings were variously attributed to the Knights Templar (who had supposedly survived their suppression to work in secret), to precursors of the Freemasons, or to ancient Druids passing down wisdom from the pre-Christian past.

There is, as it happens, some truth mixed into this fantasy. Medieval stonemasons did use geometric systems that were kept within the craft, and some imagery in churches does draw on older traditions. But the conspiracy theory version transformed technical knowledge and artistic creativity into a continent-spanning secret society manipulating Christian worship from within.

Why We Believe

It would be comforting to think that medieval people believed these things because they were ignorant—that education and scientific understanding have made us immune to such errors. But this isn't quite right.

Medieval conspiracy theories served the same psychological functions as modern ones. They explained misfortune in a world that often seemed arbitrary and cruel. They identified enemies when the real causes of suffering—disease, economic forces, the weather—were impersonal and therefore unsatisfying. They created community by defining who was inside and who was outside, who could be trusted and who must be watched.

And they were often encouraged by authorities who found them useful. Witch trials consolidated Church power. Anti-Jewish conspiracy theories distracted populations from genuine grievances against their rulers. Rumors of foreign poisoners justified wars and persecutions that served political ends.

The conspiracy theory, in other words, was not simply a mistake. It was a tool—one that could be wielded by the powerful against the powerless, but also by ordinary people trying to make sense of a bewildering world. The specific beliefs have changed, but the underlying patterns remain remarkably consistent.

We no longer worry about the Devil coordinating heretics and Jews in a continental alliance against Christianity. But we have our own versions: shadowy elites manipulating elections, corporations suppressing miracle cures, networks of evildoers embedded in institutions we should be able to trust. The faces change; the structure persists.

Perhaps the most valuable thing about studying medieval conspiracy theories is not the window they provide into the past, but the mirror they hold up to the present. The medieval mind, it turns out, looks rather uncomfortably familiar.