The Theory of Heliocentrism

Back in Florence again, Galileo no longer had to worry about money, and was thus free to pursue his research interests full-time. As had long been the case, these involved primarily terrestrial physics and astronomy. For a while, he concentrated on the former. In 1612, he published a short book about buoyancy, in which he expanded upon his dawning theories of specific gravity. Surprisingly in light of the international attention that The Starry Messenger had brought him, he chose to write this book in Italian rather than Latin, thus sharply limiting its potential readership. He would continue to write almost exclusively in his mother tongue for the rest of his life. It seems he was content to be an Italian natural philosopher, had no desire to be a continent-bestriding colossus like Tycho Brahe over the long term. And indeed, his fame would slowly decline in the rest of the Europe, even as he would remain a much-discussed and increasingly controversial figure in Italy. Bold though he was in his thoughts and opinions, he appears to have been something of a homebody, if not a rank Italian chauvinist, in his personal life. Throughout his long life, Galileo would never once leave the southern peninsula of Europe on which he had been born.

His provincialism was sometimes to the detriment of his research. By the time he returned to Florence following his second sojourn in Rome, he had already ended his brief correspondence with Johannes Kepler, by peremptorily informing his interlocutor that he intended to publish only in Italian henceforward, meaning that the two men could no longer be part of the same broader conversation. Not long afterward, a colleague from Rome took the time to write to him and tell him about Kepler’s system of elliptical orbits and the many difficulties it solved. Even now, though, Galileo gave it no serious consideration. He had convinced himself that the orbits of the planets had to be perfectly circular, not because he necessarily thought that God could only have made them that way but because he had gotten it into his head that such unending motion could only be circular according to the laws of physics.

Ironically, Galileo was arguing at the very same time that the universe was imperfect and mutable in most other ways, pointing to the sunspots he could see through his telescope, constantly moving around on the surface of the brightest heavenly body of them all, as the ultimate evidence for this. He put this argument into print for the benefit of his fellow Italians in 1613, in a pamphlet entitled Letters on the Sunspots. Elliptical orbits would have fit nicely into his emerging picture of a messy, asymmetrical universe, if only he would have taken the time to read Kepler’s book.

Even as it was, Galileo was well aware that his theories were viewed less than favorably by many on religious grounds. A prominent conservative philosopher and theologian named Ludovico delle Colombe had made it his special mission to discredit heliocentrism and everything that had sprung from it, by saying that it could in no way be reconciled with the infallible words of the Bible. Psalm 105 spoke of a God “who laid the foundations of the Earth, that it should not be removed forever.” Chronicles I said that “the world also shall be stable, that it be not moved.” Ecclesiastes said that “the Sun also ariseth, and the Sun goeth down, and hasteth to his place where he arose.” Genesis said that “God made two great lights, the greater light to rule the day and the lesser light to rule the night,” thus proving that the Moon was by nature like the Sun rather than like the Earth, as Galileo wished to claim.

Galileo responded to such arguments, very reasonably, that it was a fool’s errand to take every single word of the Bible absolutely literally.

Scripture cannot err, but its interpreters can, especially when they would always base themselves on the literal meaning of the words. For in this way not only many contradictions would be apparent, but even grave heresies and blasphemies, since then it would be necessary to give God hands and feet and eyes, and human and bodily emotions such as anger, regret, hatred, and sometimes forgetfulness of things past, and ignorance of the future.

Here we see Galileo the rapier-witted intellectual jouster displaying his talents to fine effect. The argument he makes here is subtle but persuasive, as fine a riposte to fundamentalist readings of the Bible in our own day as it was in his. He begins with a nod to the Bible’s many irreconcilable internal contradictions. (These start to show up as early as Chapter 2 of the Book of Genesis, which first says that God made the animals before making the first human, then turns around to state that he made them after Adam.) But then, perhaps knowing that this is a dangerous path to pursue too far, Galileo pivots to safer ground, pointing out how God is constantly described in human terms in the Bible, even though he is in actuality an ineffable being who, all Christians can agree, is infinitely far beyond human comprehension. These anthropomorphized depictions are metaphors, aids to human understanding, deeply imperfect though they are when applied to the splendid perfection of the divine being. If we accept scripture as metaphorical in this respect — accept that God doesn’t literally have hands and feet and eyes like we do, doesn’t really experience the world he made in anything like the way that we do — then why can we not accept descriptions of a stationary Earth and a peripatetic Sun as well as mere shortcuts to mortal comprehension?

Alas, such reasonable arguments weren’t satisfying to everyone. A slow-roiling debate about heliocentrism and the rest of Galileo’s claims took place inside the halls of power in Rome over the course of several years. In April of 1615, Cardinal Bellarmine took up his pen to offer his opinion.

The words “the Sun also ariseth, and the Sun goeth down, and hasteth to his place where he arose,” etc., were those of Solomon, who not only spoke by divine inspiration but was a man wise above all others and most learned in the human sciences and in the knowledge of all created things. His wisdom was from God, and it is not likely that he would affirm something that went against some truth that was already demonstrated or likely to be. Now, if you tell me that Solomon spoke only according to appearances, and that it seems to us that the Sun goes around when actually it is the Earth that moves, as it seems to one on a ship that the shore moves away from the ship, I shall answer that though it may appear to a voyager as if the shore is receding from the vessel on which he stands rather than the vessel from the shore, yet he knows this to be an illusion and is able to correct it because he sees clearly that it is the ship and not the shore that is in movement. But as to the Sun and the Earth, a wise man has no need to correct his judgment, for his experience tells him plainly that the Earth is standing still and that his eyes are not deceived when they report that the Sun, the Moon, and the stars are in motion.

This paragraph is a master class in circular logic; Bellarmine never bothers to clarify the nature of the “experience” that is supposed to tell his terrestrial stargazer that the Earth is standing still. Bellarmine manages to demonstrate only that he understands the relativity of impressions of motion well enough to know better.

But even as he was indulging in borderline nonsensical arguments like this, Bellarmine said that heliocentrism was fine with him if it was employed only as what was known as an instrumental system, a means of calculating the subjective positions of the heavenly bodies overhead at any given instant for purposes of timekeeping, astrology, or any other practical function. This was the reason, he said, that Nicolaus Copernicus’s On the Revolutions of the Heavenly Spheres could still be found in Church libraries. By so explicitly making it possible to view Copernicus’s universe as just an abstract system for calculation, with no necessary connection to physical truth, Andreas Osiander had done the author more of a service in his controversial preface than Georg Joachim Rheticus might ever have wanted to admit.

The debate to which we are bearing witness here is an incredibly important one about the very nature of truth and how we discern it — in fact, easily one of the most important debates in the entire history of human thought. Is truth best discerned by turning to existing sources of authority or through empirical observation and experimentation? In this present context at least, the two sides of the debate were mirror images of one another. Cardinal Bellarmine and his compatriots said that the Bible — a collection of revealed wisdom that constituted the ultimate in arguments from authority in this time and place — presented physical truth, while empirical investigation could reveal only instrumental truths, more or less useful in themselves but never to be taken literally when they came into conflict with the statements of the Bible. Galileo and his compatriots said that it was the Bible’s truths that were metaphorical — or, if you like, instrumental — while physical truth could only be discerned through empirical investigation. The epistemology that we now call science is of course predicated on this latter belief. But in the early sixteenth century, it was extremely controversial to claim the truths of science to be as or more valid than the truths of the Bible, even when it came to statements made in passing in scripture that had little to do with the major tenets of the Christian faith. For the conservatives of the Catholic Church, this was a slippery slope to be avoided at all costs. It seemed to them a small slide from saying that Solomon had been mistaken when he mentioned a stationary Earth to musing that maybe Mary hadn’t really been a virgin when she gave birth to Jesus Christ, or even that Jesus hadn’t really been the son of God. Sheared of its supernatural claim to absolute authority, the Bible would become a mere book of moral philosophy.

There lurked an existential threat to the Church  in all of these claims of Galileo — or so people like Cardinal Bellarmine believed. Every time they perused The Starry Messenger or Letters on the Sunspots, they saw another can of worms which they would rather not have opened. If, as Galileo said, the Moon was so similar to the Earth as to have mountains and valleys of its own, did that mean that it had people living on it too? And if it had people distinct from those who lived on Earth, how could they be descended from Adam? And if not descended from Adam, how could they be saved and redeemed by Jesus Christ? And if they were not saved and redeemed by Jesus Christ, how could the Church call itself “Catholic,” a word which literally meant “universal?” When you follow this chain of reasoning, it begins to seem no great wonder that Pope Paul V, one of the most unbending pontiffs of his century, placed at the heart of his agenda a policy of zero tolerance toward any notion of the Bible as a book containing anything but literal truths.

Galileo did have friends in Rome, who warned him that this was an argument he couldn’t win in the current intellectual climate, one that could be personally perilous for him to persist with. All he had to do, they said, was present his ideas as theoretical abstractions rather than physical truth, and he would be fine. Galileo responded, reasonably enough, that this would leave him muzzled and marginalized against those who denied his empirical findings: they would be able to condemn him with impunity, while he would not be able to say a word in his own defense, much less take the attack back to them.

For a verbal jouster like Galileo, this was intolerable. In December of 1615, he went to Rome to make his case in person, against the advice of many around him. A friend lamented that “he gets fired up with his own opinions, he becomes extremely passionate in his commitment to them, and he shows little strength and prudence in knowing when to get control of them, so that being here in Rome, especially as things are at the moment, is very dangerous for him. He will put himself in harm’s way, and with him all those who give him their support or allow themselves to be persuaded to do as he wants them to.” The Tuscan ambassador to Rome wrote in a letter to Galileo’s august patron Cosimo II de’ Medici that “this is no place to come and argue about the Moon and, especially in these times, arrive with new ideas.” But Galileo was determined to do just that.

He turned up in fine fettle, with his wit sharpened and primed for the joust. Feeling himself still well-protected by his closeness to the first family of Tuscany — he was staying in the Medicis’ Roman villa, and was transported around the city in a luxurious litter bearing the Medici crest — Galileo made the rounds of Rome’s intellectual upper crust, as reported in a letter written by an admiring nobleman-about-town to an unusually open-minded cardinal.

You would be delighted to hear Galileo argue, as he often does, in the midst of some fifteen or twenty persons who attack him vigorously, now in one house, now another. He is so well buttressed that he laughs them off, and although the novelty of his opinion leaves people unpersuaded, yet he shows that most of the arguments with which his opponents try to overthrow him are spurious. Monday in particular, in the house of Frederico Ghisilieri, he performed marvelous feats. What I liked most was that, before answering objections, he improved on them and added even better ones, so that, when he demolished them, his opponents looked all the more ridiculous.

This was tantamount to walking into a lion’s den and poking it with a stick; it was bound to draw the ire of Pope Paul and his most favored deputy, Cardinal Bellarmine.

Nevertheless, aware that Galileo had powerful patrons of his own, Bellarmine handled him far more cautiously than he once had Giordano Bruno. On February 26, 1616, he summoned Galileo to a meeting in his own residence, to give him fair warning and the chance to avoid a lot of unpleasantness for everyone before the Roman lion was forced to bite his head off. It would be fascinating to have witnessed this face-to-face encounter between these two leading exponents of the old and new way of discerning truth — and not just for the inherent drama of the scene. For the fact is that we do not know exactly what was demanded of Galileo at the meeting, nor what precisely he agreed to.

That said, one thing is very clear. If he had come to Bellarmine’s house expecting to engage in another sporting verbal joust, Galileo was quickly disabused of that notion. Bellarmine intended only to lay down the law. According to the Church’s official records, Galileo was ordered “to relinquish altogether the opinion that the Sun is the center of the universe and at rest and that the Earth moves; nor henceforth to hold, teach, or defend it in any way, verbally or in writing.” Galileo would later say that he remembered the injunction differently: that he must merely not claim Copernicus’s heliocentrism to be a physical — as opposed to instrumental — truth. For our part, we can only speculate about what was really said. Galileo’s 21st-century biographer David Wootton proposes that the message that was conveyed at this meeting may have been more muddled than either the official record or Galileo’s remembrance lets on, a case of both sides hearing what they most desired to hear. The Church functionaries who spoke to Galileo may not even have been entirely in agreement among themselves about what they were demanding. As we have seen, Cardinal Bellarmine had said earlier that he had no problem with Copernicus’s theory if it confined itself to the realm of instrumental truth; others who were present, who were even more reactionary than he was, may not have been willing to cede even this much ground.

At any rate, it does seem clear that the starkness of his situation came as a shock to Galileo, who prior to this point had consistently minimized the peril he was placing himself in with his loud and dogged arguments against the traditional understanding of the Bible. For his hosts’ injunctions came complete with a threat: if he didn’t agree to them, right then and there, he would be immediately arrested and handed over to the Inquisition for trial. All of Galileo’s legendary bravado seems to have deserted him the moment he heard those words. He meekly acquiesced. He had, after all, been told often of the horrors of Bruno’s last couple of hours on Earth. Now that the prospect of imprisonment and torture by the Inquisition had been laid so indelibly before him, he realized more clearly than ever that he had no desire to share that fate. And honestly, who can blame him? Galileo was not made of the stuff of martyrs. When push comes to shove, very few of us are. Faced with a choice of future abodes between a dank prison cell and a fancy Florentine villa, Galileo chose the latter.

But he was still a proud man. Perhaps because he wished to avoid the appearance of having been chased out of Rome, he did not cut his visit short. He did, however, keep a much lower profile during the second half of his stay. The same vivacious nobleman who had recently crowed about his success on the city’s debate stages now laughed about how “Galileo’s arguments have vanished into alchemical smoke, for the Holy Office has declared that to maintain this opinion is to dissent manifestly from the infallible dogmas of the Church. We now know that, instead of imagining that we are spinning in outer space, we are at rest at our proper place, and do not have to fly off with the Earth like so many ants crawling around a balloon.”

In the meanwhile, Pope Paul and Cardinal Bellarmine took steps to make geocentrism the ironclad law of the land throughout Catholic Europe. On March 5, 1616, they published an edict that would go on to become one of the most embarrassing in all the long lifetime of the Catholic Church.

The view that the Sun stands motionless at the center of the universe is foolish, philosophically false, and utterly heretical, because contrary to holy scripture. The view that the Earth is not the center of the universe and even has a daily rotation is philosophically false, and at least an erroneous belief.

That same day, a number of books advocating heliocentrism were placed on the Church’s Index of Forbidden Books for being “false and altogether opposed by holy scripture.” Surprisingly, none of Galileo’s were among them. To be included on this list was the kiss of death for any author; a pledge not to place The Starry Messenger and Letters on the Sunspots on the Index may thus have been one of the carrots that accompanied the stick of the Inquisition at Bellarmine’s meeting with Galileo. Kepler’s The New Astronomy also went unmentioned, presumably because it had received such poor distribution that Bellarmine was unaware of it. Copernicus’s On the Revolutions, the slow-rolling snowball that had gotten everyone here, was a special case, what with its undeniable usefulness for astrology. It was agreed that it would be pulled out of circulation only until certain passages which seemed to imply too plainly that heliocentrism was a physical rather than instrumental truth could be “corrected.” Said corrections, mostly amounting to no more than drawing a line through the offending sentences, would indeed be sent out to the libraries of Catholic Europe, although not until 1620. During the interim, many librarians chose to overlook the book’s presence on the Index and leave it on the shelves — an indication that, although the Church was definitely powerful in its sphere, its ability to set the terms of discourse writ large was far from absolute, especially outside of Italy.

If escaping the Index of Forbidden Books really was a carrot that Bellarmine offered to Galileo, it wasn’t the only one. He was allowed to spend an hour walking and talking in public with Pope Paul, a demonstration to the world that he had been well and truly restored to the Church’s good graces. And on May 26, 1616, as Galileo was finally preparing to leave Rome, Bellarmine provided him with a letter formally exonerating him from any charge of heresy now that he had accepted the divine truth of the Bible over the truth that he had once thought to be revealed by his telescope, that profoundly imperfect man-made instrument. All told, Galileo had done what he felt he had to in order to stay alive and out of prison. And again, before any of us rush to condemn him for it, we should ask ourselves whether we are really so certain that we would have done any differently.

Unfortunately for Galileo, his deal with Bellarmine had won him only a reprieve, not a permanent end to his tribulations. For he was still a man who liked to say what was on his mind, even as the Church was monitoring his words more closely than ever.

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(A full listing of print and online sources used will follow the final article in this series.)