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Galileo’s newly discovered letter shows his clever attempt to outsmart the Catholic Church

Galileo Galilei had a trick up his sleeve.
Galileo Galilei had a trick up his sleeve.
Image: Reuters/Tony Gentile
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When astronomer Galileo Galilei got in trouble with the Catholic Church over his theories of the universe in the 17th century, he didn’t have the benefit of a public-relations flack to help him with damage control. So he took matters into his own hands, and engaged in some old-fashioned trickery.

A newly discovered letter written by Galileo shows how the scientist attempted to get the Inquisition off his back. In an exclusive report for Nature, Alison Abbott explains that historians browsing the archives of the Royal Society have uncovered evidence that Galileo edited his own words to seem less critical of the Church.

The story begins in 1613, when Galileo wrote a famous letter defending the heliocentric model of the solar system, according to which the Earth and other planets rotate around the Sun. This theory had been proposed in 1543 by Polish astronomer Nicolaus Copernicus in his book On the Revolutions of the Heavenly Spheres, published on his deathbed. In the years since Copernicus’s death, Galileo had invented a powerful telescope and studied the heavens himself, finding evidence that the theory checked out.

This went against Church doctrine, which held that the Earth was the center of the universe—not the Sun. But in the 1613 letter Galileo wrote to his friend, the mathematician Benedetto Castelli, he said that the heliocentric model didn’t inherently contradict the Bible. Rather, “he argued that the scant references in the Bible to astronomical events should not be taken literally, because scribes had simplified these descriptions so that they could be understood by common people,” as Abbott explains for Nature.

Unfortunately, the Church was pretty into literal interpretations at the time. So when the Inquisition got ahold of a copy of the letter to Castellini in 1615, which had been forwarded by Dominican friar Niccolò Lorini, Galileo had reason to be concerned.

Here’s where our boy Galileo gets deliciously sneaky, according to the new evidence, uncovered by historians Salvatore Ricciardo, Franco Giudice, and Michele Camerota in a forthcoming article for the Royal Society journal Notes and Records. 

It seems Galileo went ahead and wrote a different, more delicately phrased version of his 1613 letter to Castelli. He then asked a friendly cleric in Rome, Piero Dini, to pass it along to the Vatican, saying that his enemies in the Church had doctored the original letter to make him look bad.

Among the key changes Galileo made to the Castelli letter, Abbott explains:

In one case, Galileo referred to certain propositions in the Bible as “false if one goes by the literal meaning of the words.” He crossed through the word “false,” and replaced it with “look different from the truth.” In another section, he changed his reference to the Scriptures “concealing” its most basic dogmas, to the weaker “veiling.”

Unfortunately, in the end the Church wasn’t so easily appeased. In 1616, the Inquisition ordered Galileo to abandon his defense of the heliocentric model. But in 1632, Galileo published the Dialogue Concerning the Two Chief World Systems, in which he compared the evidence for the Copernican system against evidence for the Church’s favored Earth-centric theory. (One guess as to which theory came out on top.)

The Inquisition put Galileo on trial. He was convicted of a “strong suspicion of heresy” in 1633, having sought to defend himself by arguing that his defense of the Copernican system was merely an intellectual exercise. He lived under house arrest until his death nine years later.

Still, the discovery offers insight into Galileo’s resourcefulness in attempting to navigate the political climate of his time while advancing scientific understanding. As Monty Python famously declared, “Nobody expects the Spanish Inquisition.” But Galileo expected the Roman one, and did his best to wriggle out from under it.