Were conspiracy theories part of the medieval world? While today’s societies are saturated with suspicions of hidden agendas, shadow governments, and secret elites, the question of whether such thinking existed in earlier centuries is more complex. Cornel Zwierlein examines the extent to which the Middle Ages laid the groundwork for modern conspiracy theories. His conclusion: although medieval Europe was full of political oaths, factional violence, and religious scapegoating, fully developed conspiracy theories—as structured, intentional narratives—were extremely rare. But they were not entirely absent.

Zwierlein, a historian teaching at Ruhr University Bochum, begins by noting that conspiracies did exist in the Middle Ages – the plots and secretive alliances that were typical of kingdoms and principalities. But as Zwierlein argues, they were not yet conspiracy theories in the modern sense. Rather than being long-form narratives that aimed to explain large-scale historical developments through secret plotting, they were real-time power struggles. What was missing in the medieval period was a narrative structure that positioned such events as part of an intentional, hidden plan with broader explanatory power.

To qualify as a conspiracy theory, according to Zwierlein, a text must not simply relay a rumour or accusation. It must be “a longer and more or less carefully, consciously and purposefully crafted text that was circulating independently within a given communication context, such as decision-making circles of early modern governments or several public sphere(s).” By this definition, the Middle Ages had few if any conspiracy theories—at least in their fully articulated form.

Anti-Jewish Conspiracy Theories

Still, Zwierlein identifies moments in the Middle Ages where conspiracy-like thinking took shape. A significant area of focus is the anti-Jewish violence that flared up across Europe during periods of crisis, such as plague epidemics or political instability. In these moments, Jews were accused of acts such as poisoning wells, conspiring with Lepers or Muslims, or desecrating Christian symbols.

Zwierlein draws on the work of David Nirenberg and others to illustrate the complexity of these episodes. He notes that historians today understand such violence not as irrational panic or as top-down manipulation by elites, but as the widespread adoption of rhetoric that served social and political purposes.

“Nirenberg demonstrated that, in the kingdom of Aragon in this period, ‘although the form and vocabulary of stereotypes about and accusations against minorities (poison, magic, sexuality, and so forth)’ were also to be found there, there is no evidence of belief in large conspiracy ‘theories’ or plots; the outbreak of – partially conscious and organised – violence has to be understood as the enactment of ‘doing and stimulating cruelty with words.’”

These events, while horrifying, typically remained episodic and local. They did not often generate durable, wide-reaching narratives that crossed borders or were reproduced in other regions. Nor were they typically framed as all-encompassing plots designed to explain broader political or religious crises.

Yet there were exceptions that suggest the early development of conspiratorial thinking. In the late thirteenth century, for example, the chronicler Richer of Sens advanced the notion of a global Jewish plot against Christianity.

“In the late thirteenth century,” Zwierlein notes, “Richer of Sens wrote in the Gesta Senoniensis Ecclesiae that ‘in the whole world the Jews commit serious crimes’, claiming that these plans were constantly elaborated and cultivated ‘in their heart’, aiming, ultimately, for the ruin of Christianity.”

This vision of a unified, trans-regional conspiracy comes closer to what Zwierlein considers an early form of a conspiracy theory. However, he is careful to point out that even this did not amount to a widely circulated, self-sustaining narrative. Such “germs” of conspiracy theory, as he puts it, “rarely transcended the text that described them to a larger narrative.”

Magic and Crusades

Zwierlein also explores other areas of medieval suspicion and accusation, such as sorcery and magic. In the fifteenth century especially, the belief that individuals or groups might use magic to harm rulers or influence events appeared in chronicles and legal trials. Sometimes these accusations were tied to actual political plots—such as imagined or attempted regicides involving magic or poison. However, Zwierlein emphasizes that these cases remained largely episodic and did not evolve into general explanatory frameworks.

Even crusade propaganda and sermons, which framed Muslims and heretics as enemies of the faith, did not typically construct detailed conspiratorial narratives. According to Zwierlein, there was little need for this: theological frameworks already provided explanations for who the enemy was and why they should be resisted. As a result, conspiracy narratives never needed to emerge in full—doctrinal categories already fulfilled that role.

Still, things began to shift in the later Middle Ages as stories emerged, hinting at more structured conspiratorial thinking. Zwierlein links this change to the growth of manuscript communication and ideological conflict, especially during the Avignon Papacy and the Great Schism. A notable example is Marsilius of Padua’s Defensor pacis (1324), which cast ecclesiastical history as a story of papal usurpation. While Marsilius aimed to offer a historical explanation rather than a conspiracy theory, his narrative—framing the Church’s evolution as a deliberate deviation—suggested “a conspiratorial character,” as Zwierlein puts it. Still, such works were shaped by theological worldviews, and not every polemical or tendentious history should be treated as a conspiracy narrative.

In sum, the Middle Ages were rich in plotting, factionalism, stereotypes, and suspicion—but lacked the media conditions and intellectual frameworks to produce the kinds of enduring, explanatory conspiracy theories that would arise in the early modern period. Zwierlein concludes that in medieval Europe, “conspiracy theories could be detected only very seldomly, and in embryonic form.”

Cornel Zwierlein’s article, “Conspiracy Theories in the Middle Ages and the Early Modern Period,” appears in the Routledge Handbook of Conspiracy Theories, edited by Michael Butter and Peter Knight, and published in 2020.

You can read more of Zwierlein’s on his Academia.edu page

Top Image: Jews burned to death in Strasbourg during the Black Death after conspiracy theories that they poisoned wells. Miniature by Pierart dou Tielt illustrating the Tractatus quartus by Gilles li Muisit (Tournai, c. 1353)