Quick answer: When the Black Death reached Europe in 1348, the medical faculty of Paris blamed a great conjunction of Saturn, Jupiter and Mars in 1345, which they held had corrupted the air. It is a striking example of how medieval mundane astrology explained epidemics. This is history, not medical or predictive advice.
Faced with the deadliest catastrophe of the age, the most learned physicians in Europe reached for the stars. Their answer was wrong, but it was not careless: it was the leading science of causes, applied with rigor to a disaster no one could stop. The episode is one of the clearest windows we have onto medieval astrology at work.
The Verdict of the Paris Masters
In October 1348, at the order of King Philip VI of France, the medical faculty of the University of Paris issued a report on the causes of the pestilence. Its first cause was celestial. On 20 March 1345, they wrote, a conjunction of Saturn, Jupiter and Mars had gathered in the sign of Aquarius, and this rare massing of the three superior planets had drawn up corrupt vapors from earth and sea, poisoning the very air that people breathed. The learned world accepted the reasoning; the conjunction became the standard first cause of the Black Death across Europe.
Great Conjunctions and the Fate of Nations
The framework was conjunctionist astrology, the reading of history by the meetings of Jupiter and Saturn. The two slowest visible planets conjoin about every twenty years, and their cycle was used to time the rise and fall of dynasties, religions and disasters. The ninth-century astrologer Abu Ma'shar had built this doctrine into a full theory of epochs, the ancestor of the great conjunctions of Jupiter and Saturn still studied today. When Mars, the lesser malefic of heat and pestilence, joined the pair, the omen turned grave. This is mundane astrology, the branch that reads the sky for whole peoples rather than persons.
Corrupted Air and the Humors
The astrology did not replace medicine; it fed it. The reigning theory of disease was miasma, the idea that epidemics spread through corrupted air. A malign conjunction was thought to spoil the air on a vast scale, and breathing that tainted air unbalanced the humors of the body, opening it to fever and death. This is why prevention focused on the air: fleeing bad places, burning aromatic woods, carrying sweet-smelling herbs. The chain ran from the heavens to the air to the humors to the sick body, each link taken from the same shared physics of qualities.
The Plague Doctor
The famous beaked costume, engraved here as Doctor Schnabel of Rome in 1656, is the miasma theory made visible. The long curved beak was packed with aromatic herbs and spices so the physician breathed only sweetened air, and the waxed coat and staff kept the corruption at arm's length. It is a later image than 1348, but it dresses the same idea the Paris masters set down: that the danger was in the air, and the air had been fouled from above.
What the Episode Teaches
Read honestly, the 1348 report is not an embarrassment but a lesson in how a coherent worldview explains a shock. Astrology was the era's science of celestial causes, and the physicians used it as carefully as their evidence allowed. They were mistaken about the cause of the plague, which we now know to be a bacterium carried by fleas, yet their method, seek the highest cause and trace it down to the body, was the reasoning of their science. It also marks a limit: this was explanation after the fact, not a forecast that saved anyone.
History, Not a Forecast
Nothing in this belongs to the present. Planetary conjunctions do not corrupt the air, cause disease or predict epidemics, and this article makes no such claim. It is a piece of the history of astrology and medicine, offered for understanding, not for guidance. For anything touching health or disease, rely on qualified medical and scientific authorities; astrology and epidemiology are entirely separate domains.
Frequently Asked Questions
Why did people blame the Black Death on a conjunction?
The Paris medical faculty, reporting in 1348, held that a conjunction of Saturn, Jupiter and Mars in 1345 had corrupted the air, which then unbalanced the humors and spread the plague. Conjunctionist astrology treated the meetings of the slow planets as causes of great events, so a rare triple massing was a natural first cause to reach for.
What is a great conjunction?
A great conjunction is the meeting of Jupiter and Saturn, which recurs about every twenty years. Medieval and Renaissance astrologers used the cycle to read the rise and fall of dynasties and eras, and when Mars joined the two the omen was read as especially severe.
Does astrology explain epidemics today?
No. The causes of disease are studied by medicine and science, not astrology, and planetary positions do not cause or predict epidemics. This article is historical, and for any matter of health you should rely on qualified medical authorities.
Explore the History
To see how the slow planets and their cycles are read in a chart, cast a free birth chart or explore the tradition through a personality report. For more classical technique explained plainly, browse the blog, and hold all of it as history and symbol, never a claim about disease or the future.
