Galileo and the Church

Galileo’s sentencing by the Inquisition was avoidable. The Church had no interest in prosecuting mathematical astronomers, but since Galileo had so little to contribute in that domain he foolishly got himself involved with Biblical interpretation. His scriptural interpretations not only got him into hot water: they are also scientifically unsound and blatantly inconsistent with his own science.

Subscribe to

Opinionated History of Mathematics

Or subscribe with your favorite app by using the address below


The Bible says basically nothing about astronomy. It has a lot more to say about righteous war. And it is in this context only that it has occasion to speak of the motions of heavenly bodies. In the Book of Joshua, we find our hero with the upper hand in battle, but alas dusk is drawing close. What a pity if some of the enemies “delivered up before the children of Israel” should be able to get away under the cover of darkness. “Then spake Joshua to the Lord,” and he said: “Sun, stand thou still.” “And the sun stood still until the people had avenged themselves upon their enemies.” That is what the Bible tells us. “The sun stood still in the midst of heaven,” so that Joshua and the chosen people could keep slaughtering infidels all night long.

This is the full extent of astronomy in the holy book. No further detail is provided anywhere in the Bible regarding the astronomical constitution of the universe or the motions of the heavenly bodies.

Obviously, serious scientists have little reason to engage with this passing and tangential allusion to cosmology in the Book of Joshua. But Galileo’s philosophical enemies saw an opportunity. By persistently and prominently accusing Galileo of proposing theories contrary to scripture they forced him into a dilemma: either let the argument stand unopposed, and hence let his enemies have the last word, or else get involved with the very dangerous matter of scriptural interpretation. Galileo foolishly took the bait. Now all the Aristotelians had to do was to sit back and watch Galileo march to his own ruin in this minefield.

So let’s see how Galileo proposes that we interpret the Biblical passage about the sun standing still. His interpretation is nuts. It is a prime example of his shameless drive to score rhetorical points at any cost. It is perfectly reasonable to argue that the phrase about the sun “standing still” should not be taken too literally. Indeed, it is commonly accepted, as Galileo observes, that various things in the Bible “were set down in that manner by the sacred scribes in order to accommodate them to the capacities of the common people, who are rude and unlearned.”

Indeed, if the Bible is read literally, “it would be necessary to assign to God feet, hands, and eyes,” as Galileo says. But those passages are only figures of speech, according to orthodox Christian understanding. When the Old Testament says that the commandments handed to Moses were “written with the finger of God,” the intended takeaway is of course not that God has an actual physical finger and that he needs it to write. It doesn’t make a whole lot of sense that he could create the entire universe in under a week, or flood the entire earth at will, yet if he has to write something down he has to painstakingly trace it out in clay with his finger.

So perhaps it is the same with the sun “standing still.” It’s just a phrase adapted to everyday speech, not a scientific account. In fact, even Copernicus himself speaks of “sunrise” and “sunset,” as Galileo points out, even though the sun doesn’t move in his system. So it is hardly unreasonable to think that “the sacred scribes” used this kind of common parlance as well, even if they knew that the sun is always stationary.

That’s all fine and well. But Galileo does not stop with this balanced and reasonable point. Instead he makes the outlandish claim that the Joshua passage in fact literally agrees best with heliocentrism rather than geocentrism:

“If we consider the nobility of the sun I believe that it will not be entirely unphilosophical to say that the sun, as the chief minister of Nature and in a certain sense the heart and soul of the universe, infuses by its own rotation not only light but also motion into other bodies which surround it. So if the rotation of the sun were to stop, the rotations of all the planets would stop too. [Therefore,] when God willed that at Joshua’s command the whole system of the world should rest and should remain for many hours in the same state, it sufficed to make the sun stand still. In this manner, by the stopping of the sun, the day could be lengthened on earth—which agrees exquisitely with the literal sense of the sacred text.”

This is a terrible argument. It is so unscrupulous that its absurdity can be exposed simply by quoting the words of Galileo himself, written in another context, in his Dialogue:

“If the terrestrial globe should encounter an obstacle such as to resist completely all its whirling motion and stop it, I believe that at such a time not only beasts, buildings, and cities would be upset, but mountains, lakes, and seas, if indeed the globe itself did not fall apart. This agrees with the effect which is seen every day in a boat travelling briskly which runs aground or strikes some obstacle; everyone aboard, being caught unawares, tumbles and falls suddenly toward the front of the boat.”

So in this manner “Joshua would have destroyed not only the Philistines, but the whole earth,” if stopping the sun meant stopping the motion of the earth, as Galileo claims. Not to mention that the idea that the sun’s rotation on its axis is the only thing moving the planets is completely unsubstantiated in the first place. It seems that Galileo pretended to believe in this principle on this occasion solely for the sake of being able to make this scriptural argument. The hypocrisy and unbridled opportunism of Galileo’s forays into biblical interpretation are plain to see.

It is very difficult, if not impossible, to see his interpretation of the Joshua passage as a scientific argument that Galileo genuinely believed. The second quote I read, about everything collapsing like a house of cards if the earth stopped, that is from 15 years later. But surely Galileo realised this all along. If he didn’t, he was stupid. If he did, then he was clearly perfectly happy to fabricate scientifically nonsensical lies as long as it helped him score a satisfying rhetorical point.

This just goes to show how little all of this had to do with science. Galileo’s interpretation of the Joshua passage is terrible science, and he probably knew that perfectly well. This was a conflict between science and religion if by “science” you mean the ludicrous idea that stopping the sun’s rotation would immediately stop the earth dead in its tracks, and that the people on the earth would suffer no consequences of this whatsoever except that the day would became longer. This is the “science” in science versus religion, if we go by what Galileo wrote.

It was only because Galileo got involved with biblical interpretation that he ended up in the crosshairs of the Inquisition. Nobody minded mathematical astronomy, but the question of who has the right to interpret the Bible was the stuff that wars were made of. Luther challenged church authority and emphasised personal understanding of the Bible—“sola scriptura,” as the motto went. This was the core belief of protestantism, and eradicating protestantism was top of the agenda for the catholic church. This is right in the middle of the Thirty Years’ War, which was centered on this core conflict between protestantism and catholicism. A devastating war, comparable to the world wars in terms of per capita deaths.

Once Galileo’s enemies baited him into commenting on the Bible, it was all too easy for them to connect Galileo’s otherwise harmless dabbling to this heresy du jour. Because of the war and raging conflict, this was a matter on which the church could not afford to show any weakness.

There is only one mystery: Why did Galileo walk straight into such an obvious trap? The answer lies, as ever, in his mathematical ineptitude. Galileo was told by church authorities that “if he spoke only as a mathematician he would have nothing to worry about.” Galileo would presumably have followed this advice if he could. The problem, of course, was that he did not have anything to contribute “as a mathematician.” Since a mathematical defence of heliocentrism was beyond his abilities, Galileo was left with no other recourse than to roll the dice and try his luck in the dangerous and unscientific game of scriptural interpretation.

So the church was reluctantly drawn into these astronomical squabbles and had to do something. The Inquisition settled for a slap on the wrist: in the future, Galileo must not “hold, teach or defend [the Copernican system] in any way whatever,” they decided. They also ordered mild censoring of Copernicus’ book, namely the removal of a brief passage concerning the conflict with the Bible and a handful expressions which insinuated the physical truth of the theory. That was it. No book bans, no imprisonments. And Galileo got away with just a warning.

Galileo did indeed keep quiet for a number of years after being ordered to do so by the Inquisition. But times changed. After waiting for over a decade, Galileo felt it was safe to try the waters again. A new Pope was in power, Urban VIII, who was quite liberal. He even said of the 1616 censoring of Copernicus that “if it had been up to me that decree would never have been issued.” Galileo had good personal relations with this new open-minded Pope. So Galileo sensed an opening and obtained a permission to publish the Dialogue in 1632. Or rather, as the Inquisition would later put it, he “artfully and cunningly extorted” this permission to publish. For when the permission was granted the Pope did not know about the private injunction of 1616 for Galileo to keep off the subject. When this came to light the Pope was outraged and felt, with good cause, that Galileo had been deliberately deceitful and reportedly stated that “this alone was sufficient to ruin [Galileo] now.”

So the wheels of the Inquisition were in motion again. A special commission was appointed. It found many inappropriate things in the Dialogue, but this was not a major issue, they noted, for such things “could be emended if the book were judged to have some utility which would warrant such a favor.” The real problem was instead that Galileo “overstepped his instructions” not to treat heliocentricism.

The same report also points out that Galileo had disrespected the Pope on another point as well. The Pope had asked Galileo to include the argument that since God is omnipotent he could have created any universe, including a heliocentric one. So even though the church does not agree with Copernicus, their own logic, namely belief in God’s omnipotence, can be used to legitimate at least considering the possibility of this hypothesis. So that’s a useful argument that Galileo could have used to try to find at least a little bit of common ground with his opponents. But instead of using it for such purposes of reconciliation as intended, Galileo used it to fuel the fires of conflict even more. He made had placed the Pope’s favourite argument “in the mouth of a fool,” the commission observed. He made Simplicio, the dumb character in the Dialogue who constantly expresses the wrong ideas and is proven wrong at every turn, be the one who spoke the Pope’s words. He hardly did himself any favours with this disrespectful move.

Following these findings, the second Inquisition proceedings took place in 1633: 17 years after the first Inquisition where Galileo had gotten off easy, and the year after the publication of his inflammatory Dialogue in defence of Copernicanism. The outcome was a forgone conclusion. Galileo’s defence was transparently dishonest. He pretended that, in the Dialogue, “I show the contrary of Copernicus’s opinion, and that Copernicus’s reasons are invalid and inconclusive.” This is of course pure nonsense. In private correspondence shortly before, Galileo had spoken more honestly, and stated that the book was “a most ample confirmation of the Copernican system by showing the nullity of all that had been brought by Tycho and others to the contrary.” But now before the Inquisition he had to pretend otherwise. In light of the accusations, Galileo continued, “it dawned on me to reread my printed Dialogue,” and “I found it almost a new book by another author.” These transparent lies did little to save him. He was forced to abjure. The Dialogue was prohibited, but not for its contents but rather, in the words of the Inquisition’s sentence, “so that this serious and pernicious error and transgression of yours does not remain completely unpunished” and as “an example for others to abstain from similar crimes.”

There is a popular myth that Galileo muttered “eppur si muove”—”yet it moves” (the earth moves, that is)—as he rose from his knees after abjuring before the Inquisition. But this is certainly false. Obviously the Inquisition would not have tolerated such insubordination, especially since the whole point the trial in the first place was to punish Galileo for his defiance. Galileo had been shown the instruments of torture, and such a rebellious exclamation would have been the surest way to have them dusted off for the occasion. Today no historian believes the myth that Galileo mumbled these words before the Inquisition. Yet it remains instructive in warning us of the lengths many Galilean idol worshippers are willing to go to, who do not want to admit the many ignominious historical facts about their hero. The sheer multitude of such myths now universally regarded as busted should leave us open to the distinct possibility that we have not gotten to the end of them yet.

A similar myth, which has been appealing to anti-religion ideologues, is that “the great Galileo groaned away his days in the dungeons of the Inquisition, because he had demonstrated the motion of the earth.” That’s a quote from Voltaire. But in reality Galileo was sentenced more for his provocateurism than for his science, and furthermore he was never imprisoned in any “dungeon.” He was sentenced to house arrest. A visitor “reported that [Galileo] was lodged in rooms elegantly decorated with damask and silk tapestries.” Soon thereafter he retired to “this little villa a mile from Florence,” where “nearby I had two daughters whom I much loved” and where he also received many friends and guests. Many today would pay dearly for such a retirement. Galileo got it as a so-called “punishment.”

So that’s the story of the Inquisition proceedings. Let’s look at some lessons from this.

Galileo’s conflict with the church was entirely unnecessary. It arose precisely because Galileo was a lampooning populariser rather than a mathematical astronomer and scientist. “[Galileo] was far from standing in the role of a technician of science; had he done so, he would have escaped all trouble,” as Santillana says in his book, The Crime of Galileo. The church establishment had no interest in prosecuting geometers and astronomers. Copernicus’ book had long been permitted, and Galileo’s own Letters on Sunspots of 1613 had been censored only where it referred to scripture, not where it asserted heliocentrism. In reality, “a major part of the Church intellectuals were on the side of Galileo, while the clearest opposition to him came from secular ideas” and philosophical opponents.

Today many take for granted that a fundamental rift between science and religion was unavoidable. Some have imagined for instance that Galileo defied the worldview of the church by demoting the earth from its supposedly “privileged” position. 20th-century playwright Bertolt Brecht appreciated the dramatic flare of framing the conflict in such terms when he wrote a play about Galileo. He has one of the characters argue the privilege point passionately:

“I am informed that Signor Galilei transfers mankind from the center of the universe to somewhere on the outskirts. Signor Galilei is therefore an enemy of mankind and must be dealt with as such. Is it conceivable that God would trust this most precious fruit of his labor to a minor frolicking star? Would He have sent His Son to such a place? The earth is the center of all things, and I am the center of the earth, and the eye of the Creator is upon me.”

But historically this is nonsense, to be sure. Nobody was concerned about this at the time. In fact, classical cosmology clearly stipulated that the Earth was not at all in a privileged position but rather condemned to its very lowly place in the universe. Doesn’t everybody know that hell is just below the surface of the earth, while heaven is way up above? Clearly, then, being at the center of the universe is nothing to be proud of.

It was a commonplace argument in Galileo’s time “that the earth is located in the place where all the dregs and excrements of the universe have collected; that hell is located at the centre of this collection of refuse; and that this place is as far as possible from the outermost empyrean heaven where the angels and blessed reside.” That’s a quote from a book review in the latest issue of the Journal for History of Astronomy. You can go there and find entire books about this.

Even Galileo himself added to the pile of such descriptions. Here is what he says: “after the marvellous construction of the vast celestial sphere, the divine Creator pushed the refuse that remained into the center of that very sphere and hid it there lest it be offensive to the sight of the immortal and blessed spirits.”

Many of Galileo’s contemporaries reasoned alike. Let me quote one more such example: considering “the Vileness of our Earth,” it “must be situated at the center, which is the worst place, and at the greatest distance from those Purer and incorruptible Bodies, the Heavens.” That’s a quote from John Wilkins, an Anglican bishop. This is obviously the very opposite of the argument retrospectively imagined by Brecht and other modern minds, about the supposedly privileged position of the earth.

Here’s another take you sometimes hear: Maybe Galileo brought revolutionary progress by outlining the modern conception of the relation between science and religion. Was it Galileo who showed how faith and science can coexist? How they need not undermine or conflict with one another since one is about the spiritual and the other about the physical? Galileo indeed makes such a case. But those points are common-sense platitudes, not a new vision for the place of science in human thought.

Let’s listen to Galileo’s words from his famous and widely circulated Letter to Duchess Christina of 1615. Here is what Galileo says:

“Far from pretending to teach us the constitution and motions of the heavens and the stars, the authors of the Bible intentionally forbore to speak of these things, though all were quite well known to them. The Holy Spirit has purposely neglected to teach us propositions of this sort as [they are] irrelevant to the highest goal (that is, to our salvation). The intention of the Holy Ghost is to teach us how one goes to heaven, not how heaven goes.”

Even a recent Pope praised Galileo for his supposed insight on this subject: “Galileo, a sincere believer, showed himself to be more perceptive [in regard to the criteria of scriptural interpretation] than the theologians who opposed him.” That’s Pope John Paul II, who said this in 1992.

I disagree with this papal statement on two grounds. First of all, Galileo was not pioneering a new vision for the roles of science and religion more perceptively than anyone else. Rather, he was merely recapitulating elementary ideas that were virtually as old as organised Christianity itself. McMullin has a chapter on this in the Cambridge Companion to Galileo. He concludes that: “[Galileo’s] exegetical principles were not in any sense novel, as he himself went out of his way to stress. They were all to be found in varying degrees of explicitness in Augustine”—twelve centuries before Galileo—”and, separately, they could call on the support of other [even] earlier theologians.” Galileo indeed quotes at great length from Augustine and the church fathers. Not that Galileo knew anything about the history of biblical interpretation: “He had no expertise whatever in that area, so he evidently asked his Benedictine friend, Castelli, to seek out references that would support the exegetical principles he had outlined.” So there was no novelty or insight in Galileo’s treatment of the relation between science and religion.

And here’s a second reason to disagree with the Pope. It is highly doubtful whether Galileo genuinely was “a sincere believer,” as he purported to be. David Wootton has made a compelling case for “two Galileos, the public Catholic and the private sceptic.” Here’s his argument:

“The only decisive document we have [is a 1639 letter to Galileo from] Benedetto Castelli, Galileo’s old friend, former pupil and long-time intellectual companion. … If anyone was in a position to know if Galileo was or was not a believer it was Castelli. … [Castelli writes in his letter that he] has heard news of Galileo that has made him weep with joy, for he has heard that Galileo has given his soul to Christ [in his old age—Galileo was 75 at this point]. Castelli immediately refers to the parable of the labourers in the vineyard: even those who were hired in the last hour of the day received payment for the whole day’s work. … Then … he turns to the crucifixion, and in particular to the two thieves crucified on either side of Christ. One confessed Christ as his saviour and was saved; the other did not and was damned. … Castelli’s [point] is clear and unambiguous. He believes Galileo is coming to Christianity at the last moment, but not too late to save his soul. There is no conceivable interpretation of this letter which is compatible with the generally held view that Galileo was, throughout his career, a believing Catholic.”

That’s David Wootton’s argument in his book on Galileo. It is not a mainstream view but I am inclined to believe it.

The Cambridge Companion to Galileo poses for itself the question: “What did Galileo actually do that made his image so great and so long-standing?” Its answer is not a list of great scientific accomplishments but rather: “Certainly his was the first main effort that fired the vision of science and the world that went well beyond limited intellectual circles.” Galileo was a populariser, in other words. “It was to the man of general interests that Galileo originally addressed his works,” as Stillman Drake says. Indeed, Galileo embraced this role, praising himself for “a certain natural talent of mine for explaining by means of simple and obvious things others which are more difficult and abstruse.”

I agree with these learned authors that Galileo wrote for the vulgar masses. I must add only one point, which they omit, namely that Galileo was driven to turn to popularisation because he was so bad at mathematics. “Galileo scarcely ever got around to writing for physicists,” Drake says. Yes, and he was scarcely able to do so either. The two are not unrelated.

Take for instance the “new stars” (or supernovas, as they would be called today) that appeared in Galileo’s lifetime. One appeared in 1572. It was studied with great care by Tycho Brahe. Another appeared in 1604, when Galileo was 40 years old and an established professor of mathematics. But Galileo didn’t make a contribution based on serious astronomy as Tycho had done. Instead he gave public lectures on the nova to a layman audience totalling more than a thousand people. This is precisely the difference between Galileo and the mathematicians. In modern terms, Galileo is less of a scientist and more of a presenter of TV specials.

Galileo’s little science extravaganzas were a hit at bourgeois dinner parties. Here’s how a contemporary witness describes it:

“We have here Signor Galileo who, in gatherings of men of curious mind, often bemuses many concerning the opinion of Copernicus, which he holds for true. He discourses often amid fifteen or twenty guests who make hot assaults upon him. But he is so well buttressed that he laughs them off; and although the novelty of his opinion leaves people unpersuaded, yet he convicts of vanity the greater part of the arguments with which his opponents try to overthrow him. What I liked most was that, before answering the opposing reasons, he amplified them and fortified them himself with new grounds which appeared invincible, so that, in demolishing them subsequently, he made his opponents look all the more ridiculous.”

Again: Galileo’s speciality is burlesque astronomical road shows, not serious science. If you are an Italian aristocrat who enjoys seeing the learned establishment lose face but don’t want to rock the boat yourself, then you can live vicariously through Galileo’s snappy comebacks and provocations. To this end it matters little whether they are scientifically sound or not.

This is the context in which we must understand Galileo’s conflict with the Church. If we want a parallel of the Galileo trials today we should not think of some totalitarian regime imprisoning intellectuals. A better parallel is cancel culture in popular media. Galileo is a charismatic TV personality. Many enjoy listening to him make fun of the other team. But sometimes he is politically incorrect. So his enemies organise a social media campaign, making a lot of noise. And Galileo is too hot-headed for his own good so he joins in the mud-fight with a bunch of @-replies on Twitter that he didn’t vet with his legal department first. That’s exactly what his opponents were fishing for, and now they got their gotcha quotes that they can take to the network executives and get Galileo cancelled.

Altogether a regrettable spectacle, but one that has not all that much to do with science.