The story of the conflict between Galileo Galilei and the Catholic Church is a classic one, often cited as primary evidence for the historical conflict between science and religion. In 1992, after 359 years, the Church finally admitted that Galileo was right. Here is a quick summary of the affair in the New Scientist:

In 1633, the Inquisition of the Roman Catholic Church forced Galileo Galilei, one of the founders of modern science, to recant his theory that the Earth moves around the Sun. Under threat of torture, Galileo – seen facing his inquisitors – recanted. But as he left the courtroom, he is said to have muttered, ‘all the same, it moves’.

This is the Hollywood version of history. Galileo never muttered the famous line, “all the same, it moves” or any version of it (at least there is no record of such a statement, and how could there be?). It is also not accurate to say that Galileo recanted under threat of torture. But – the core of the story, it turns out, is true. Here is the short version from Creation.com:

The reality, however, is quite different. At the time of Galileo’s trial, the scientific evidence did not support his assertion that the earth moves, and his ‘proof’ that it did was based on a flawed argument. It was only many years later that scientists were able to confirm that he was right. Galileo was foolish and arrogant in the way he argued his case; he made enemies unnecessarily and threatened the establishment’s hold on the education system. Even at the time, many considered that he was the victim of politics rather than attempts to safeguard Christian doctrine.

This version of events is completely false. This is the equivalent of saying that the American civil war was not really about slavery. Fortunately, the trial of Galileo is a well-documented event. This is one advantage of having an institution that survives for centuries – they can keep accurate records. We actually have transcripts and reports from the trial itself, and letters written by the key players, including Galileo. Galileo was already famous at the time, and there was great interest in the trial. The Church itself wanted the results of the trial to be widely known – that was kinda the idea.

Here is a great summary by Richard Blackwell who walks the reader through the trial and cites the key documents to support his narrative. The documents really leave zero doubt as to the big picture. Of course, there is always more complexity. I’m sure there was a lot of politics and backroom dealing going on that did not get documented, but nothing could change the broad brushstrokes of what happened. I will give a much briefer summary, but if you are interested in all the details read Blackwell’s article. It is interesting reading and not that long.

The primary charge of the Inquisition against Galileo was heresy, that he himself believed in the heliocentric Copernican model of the universe, and that he promoted that belief through his book, Dialogue Concerning the Two Chief World Systems. This was published in 1632, and was fashioned after a Platonic dialogue. There are three characters: Salviati, who effectively defends the Copernican system, Simplicio, who stubbornly defends the geocentric system, and Sagredo, a neutral third party who wants to hear the arguments and is there to ask questions. I actually took an entire course on this book in College – there is no question that Galileo favored the heliocentric system. Even the same, “Simplicio”, was meant to convey that he was a simpleton. But the deliberate brilliance of writing the book as a dialogue was plausible deniability, and that was a central point to the Inquisition trial.

The first part of the trial centered around the question of whether or not Galileo violated the orders of the Church based upon a Decree from 1616. The prosecutor had the Decree from the Pope which essentially said that spreading Copernicanism was banned. Here is the relevant quote, so that there is no doubt about this:

It has come to the attention of this Sacred Congregation that the Pythagorean doctrine of the mobility of the earth and the immobility of the sun, which is false and completely contrary to the divine Scriptures, and which is taught by Nicholas Copernicus in his De revolutionibus orbium coelestium and by Diego de Zuñiga in his Commentary on Job, is now being divulged and accepted by many….Therefore, lest this opinion spread further and endanger Catholic truth, it is ordered that the said Nicholas Copernicus’s De revolutionibus orbium and Diego de Zuñiga’s Commentary on Job are suspended until corrected; also that the book of the Carmelite Father Paolo Antonio Foscarini is completely prohibited and condemned; and also that all other books teaching the same thing are prohibited, as the present Decree prohibits, condemns, and suspends them all respectively. (Blackwell 1991, 122)

That’s pretty clear. This seems to therefore be an open-and-shut case against Galileo. But, Galileo brought his own document to the court. He had a letter written to him in 1616 from Cardinal Bellarmine which said that it was permissible to talk about the heliocentric idea as a hypothesis, as long as you don’t go so far as to say that it was actually true, and that you don’t believe it yourself.  This created an impasse of dueling documents, and there was no resolution. Later in the trial, however, Galileo weakened his position, for some reason, by saying that it is possible he was given verbally stronger restrictions by the Church but doesn’t remember because it was so many years ago.

The second point of the trial was whether or not Galileo violated Church law by publishing the book at all. But, Galileo had obtain an “imprimatur” (literally, “let it be published”) on two separate occasions. So twice the Church said it was OK to publish the book, and so could hardly condemn Galileo from doing so. The prosecutor and the Inquisition were heading for an embarrassing outcome to their trial, and they knew that the world was watching.

The final point of the trial was what Galileo believed himself, because if he believed in heliocentrism, that is heresy. This is where torture comes in, because the Inquisition had recently started using torture to determine what suspects truly believed. The Pope, who was a personal friend of Galileo’s, ordered that Galileo, due to his advanced age and poor health, not be tortured but only the threat of torture be used.

In any case, this is where the wheeling and dealing starts. Galileo insisted that the Dialogue was not an argument for heliocentrism (this is the plausible deniability) but just a discussion. In fact, he maintained, that he presented the arguments for heliocentrism so that they could be refuted. Anyone reading or studying the book would have a hard time accepting this interpretation – Galileo clearly favored heliocentrism. The final agreement, to get around the impasse, was that Galileo would officially state that he did not believe in heliocentrism, and that the Dialogue was not meant to promote heliocentrism. This is what he said:

Now I freely confess that it appeared to me in several places to be written in such a way that a reader, not aware of my intention, would have had reason to form the opinion that the arguments for the false side, which I intended to confute, were so stated as to be capable of convincing because of their strength, rather than being easy to answer. (Finocchiaro 1989, 278)

I think today this would be characterized as a “notpology”. He accidently overstated the arguments for heliocentrism so that an unwary reader might misconstrue his purpose. OK, sure. He was also convicted of “possible heresy” rather than actual heresy, a lesser crime that does not require execution. He was sentenced to prison, where he spent one day and then the sentence was commuted to house arrest, where he spent the rest of his days. The Church then widely publicized their version of events, saying that the famous Italian scientist, Galileo, says the church and geocentrism are correct.

There is a lot more detail, but these are the important bits. The key lessons remain intact – The Church gave itself the authority to proclaim what books could be published, what arguments could be put forward, and even what people were allowed to think and believe. Everything must conform to their interpretation of “Holy Scripture”. They jealously guarded their authority, and would prosecute, even unto death, any heresy. But it is also true that the Catholic Church, despite its structure, was not monolithic – there were many orders and opinions within the Church, and the Church was not uniformly anti-science. In fact, they promoted science and scientific thought in many ways. The Jesuits, in particular, were very academic. But in the end, the Pope and his advisors determined what was heresy, and would not allow any thought that violated dogma.

Despite all this, Galileo won in the end. His ideas prevailed, at least the ones that were correct. He did popularize heliocentrism, and the Dialogue remains a classic of literature. While more complex and nuanced than the simple version, the story, at its core, does reflect the conflict between science and religion, between dogma and scientific freedom, and between arguments from authority and arguments based in logic and evidence.