In 1348, Philip VI sought plague answers—but not from doctors

The King's Strange Commission

On October 6, 1348, King Philip VI of France ordered the Faculty of Medicine at the University of Paris to investigate the cause of the pestilence sweeping his kingdom. But the monarch made an unusual demand: he wanted an astrological explanation, not a medical one. The resulting document, known as the Compendium de Epidemia, was completed by October 1348 and blamed the catastrophe on a planetary conjunction that had occurred more than three years earlier. At precisely 1:00 PM on March 20, 1345, the report claimed, Saturn, Jupiter and Mars had aligned in the sign of Aquarius, corrupting the earth's atmosphere and igniting poisonous vapors. The fifty-page treatise devoted only a handful of paragraphs to symptoms and remedies—the rest was astronomy, geometry and meteorology, complete with diagrams of celestial mechanics. Philip wasn't asking for a cure; he was commissioning a cosmic alibi that would absolve earthly rulers of responsibility for the worst mortality event in recorded history.

How Medieval Medicine Became Stargazing

The Compendium's authors were physicians, but they wrote like astrologers because that's what the king—and the era—expected. Medieval medical theory held that the heavens governed earthly health through the balance of four humors: blood, phlegm, yellow bile and black bile. Any catastrophic illness must therefore have a celestial trigger, and the 1345 conjunction fit perfectly. Saturn was cold and dry, Jupiter hot and moist, Mars hot and dry—their meeting in an air sign would naturally produce corrupted winds and miasmas. The report even cited Aristotle's Meteorologica to explain how earthquakes released subterranean vapors that rose to mix with the tainted air. The physicians recommended prayer, purging, and avoiding bad smells, but spent far more ink calculating angles between planets than discussing contagion. The document never mentioned rats, fleas, or person-to-person transmission—concepts that wouldn't emerge for centuries. Instead, it described a mechanical universe where geometry determined mortality, and kings could deflect blame skyward.

The Report That Defined an Era's Understanding

The Compendium became the single most influential explanation of the Black Death in medieval Europe, copied and translated into vernacular languages across the continent. Dozens of surviving manuscripts testify to its reach: versions appeared in English, French, German, Italian and Dutch, circulating among physicians, clergy and educated laypeople from London to Prague. When other kingdoms sought to understand the plague, they simply copied Paris's answer—sometimes verbatim, sometimes with local amendments blaming additional conjunctions or comets. The text's authority rested on its source: if the greatest medical faculty in Christendom said the stars were to blame, who could argue? This single commission shaped European intellectual responses for decades, embedding astrology so deeply into plague discourse that even skeptical physicians felt compelled to acknowledge planetary influences. The report's legacy was profound: it postponed serious investigation of contagion mechanisms, reinforced fatalism about divine or cosmic will, and gave rulers a ready-made narrative that transformed a public health disaster into an act of the heavens.

Why It Still Matters

The Compendium de Epidemia stands as a cautionary tale about how authority figures commission explanations that serve political ends rather than truth. Philip VI didn't want medical advice; he wanted a story that made the plague an inevitable cosmic event beyond any king's control. The document he received did exactly that, and its widespread acceptance reveals how narratives from prestigious institutions can shape collective understanding for generations—even when those narratives are fundamentally wrong. Modern historians see the report as a missed opportunity: the Faculty of Medicine had access to clinical observations from across Europe, but chose to ignore ground-level evidence in favor of celestial geometry that confirmed existing worldviews. The episode demonstrates how crisis responses often tell us more about power, anxiety and institutional incentives than about the crises themselves. Today's public health officials still grapple with the same dynamic—the pressure to provide explanations that comfort authority rather than confront uncomfortable realities.