Hi, I'm Peter Adamson, and you're listening to the History of Philosophy podcast, brought to you with the support of the Philosophy Department at King's College London and the LMU in Munich.

Online at historyofolosophy.net.

Today's episode, The Men Who Saw Tomorrow, Renaissance Magic and Astrology.

When I was about 10 years old, I saw a documentary on television called The Men Who Saw Tomorrow, about the 16th century astrologer and suzerre Michel de Notre Dame, also known as Nostradamus.

It credited him with accurately predicting many historical events, from the French Revolution to the Kennedy assassination, and went on to suggest that he had also predicted a nuclear apocalypse in the decade to come.

I was absolutely terrified, still today I can remember being unable to sleep, convinced that World War III had already been foreseen in the Renaissance.

So I can imagine pretty well how people back in the Renaissance felt in the 1420s, when a number of astrologers warned of a great flood, owing to a conjunction of Mars, Saturn, and Jupiter in the sign of Pisces.

After the resulting panic proved to be unfounded, Martin Luther pointed out that, whereas the flood hadn't happened, there was a huge peasant uprising instead, of this no astrologer had breathed so much as a word.

Nowadays, most people over the age of 10 chuckle at the idea that astrological predictions could be accurate, even if most of us also know our star signs and peak at the horoscopes in the newspaper now and again.

But in the 15th and 16th centuries, as in antiquity in the Middle Ages, there was widespread, sincere belief in the efficacy of astrology, and the closely related practice of magic.

This conviction could be found at the highest echelons of society. You might recall that Christine de Pizzan's father was a professor of astrology, and went with his family to the court of Charles V, whom Christine called, wa-assolo-jien.

Predictions based on this science could enhance political legitimacy or have the reverse effect, which is why it was possible to get in serious trouble for predicting the death of rulers and popes.

In a study of the use of astrology in Milan, the scholar Monica Azzolini has shown how members of the powerful Sforza family retained astrologers to advise them.

When the sickly John Galiatso Sforza died prematurely in 1494, his doctors explained their failure to keep him alive in astrological terms. His modest life span was foretold and his nativity.

Still, they did their best to ward off this fate, constantly consulting the stars, at one point delaying treatment until a conjunction of the moon with Mars had passed.

But this noble patient's death was inevitable due to the terrible influence of the heavens. Besides which, John Galiatso refused to stop eating dangerous fruits, like pears, plums, and apples.

Had he also partake in a melon, the doctors would probably have considered it a suicide.

We can see from this example that astrology was closely connected to medicine. To cast the horoscope of one's patient was like taking a medical history, and observation of the stars could influence both diagnosis and prognosis.

This is illustrated well by the controversial notion of critical days, which goes all the way back to hypocrites and Galen.

Both ancient doctors asserted that there are pivotal junctures in the development of an illness, which fall on days 7, 14, and 20, when the patient will either take a turn for the worse or begin to recover.

Galen proposed that critical days are determined by the cycle of the moon, which is divided into periods of somewhat less than seven days, which is why the third critical day is the 20th and not the 21st.

Unfortunately, his explanation of the astronomy governing this was not very convincing, in part because he failed to take account of variation in lunar cycles, so attempts were made to fix up the theory.

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