by Mario Livio
Let’s, however, think for a moment about what Galileo’s friends and all the Church officials who were not (at least not yet) unsympathetic to him were advising him to do. In Galileo’s view, even though at that point he still lacked direct proof for the Earth’s motion, his discoveries had already achieved two things: First, some of the arguments of those who had claimed they had proof that the Earth was not moving (such as, that the Earth would have lost its Moon) had largely been shown to be false. Second, Galileo’s findings constituted for him so much of a “smoking gun” for the Copernican system that there was no question in his mind that this model had to be considered as being at least potentially correct. And correct not just as some mathematical abstraction that happened to somehow mimic nature, but as a true description of physical reality.
Galileo was fighting here opinions frozen by centuries in which science had been considered detached from observations. The term “to save the appearances” had been coined to describe scientific models that conveniently simplified observations but had no deeper significance. Bellarmino, Grienberger, Barberini, and others were asking Galileo to give up convictions that had been forged on the basis of painstaking scientific observations and brilliant deductions, only because they appeared to contradict some sacred, ancient, vague, poetic texts—and only when those texts were interpreted literally rather than figuratively. In other words, it is not true that Bellarmino and Grienberger were trying only to convince Galileo not to meddle in theology, as a few modern scholars have concluded. This is demonstrated, for instance, by the fact that when addressing the arguments that Galileo had presented in favor of Copernicanism, Grienberger told Dini that he was “worried about other passages of the Holy Writ,” and Bellarmino specifically mentioned that the Copernican doctrine should be presented solely as a pure mathematical expedient. Far from being annoyed merely by Galileo playing the theologian and his foray into biblical exegesis, these individuals were quite intent on crushing the Copernican challenge as a representation of reality because, from their perspective, they were vindicating the authority of Scripture in determining truth.
Can one be surprised, then, that Galileo refused to cooperate, at least initially? Should he have abandoned what he regarded as the only possible logical conclusions in favor of what amounted to a seventeenth-century version of political correctness? Recall that Galileo was right after all. Galileo never raised any doubts about the veracity of the biblical texts. At that point, he was still hoping for reason to prevail, and he did his best to prove that while interpretations of Scripture could be reformulated in alternative ways so as to agree with what nature was presenting, facts were facts.
UNEXPECTED SUPPORT WITH UNEXPECTED CONSEQUENCES
Galileo’s more open support for Copernicanism, starting in 1615, which went against the judgment of his friends and the advice he had received from church officers, was likely motivated, influenced, and encouraged by a surprising booklet published by Carmelite theologian Paolo Antonio Foscarini.
A native of Montalto Uffugo in Calabria, Foscarini had been known to have broad knowledge in topics ranging from theology to mathematics. Cesi sent Galileo a copy of Foscarini’s book on March 7, 1615. The very short publication had a very long title, part of which read Letter of the Reverend Father Master Antonio Foscarini, Carmelite, on the Opinion of the Pythagoreans and of Copernicus Concerning the Mobility of the Earth and the Stability of the Sun and the New Pythagorean System of the World, etc. The title referred to the fact that the first nongeocentric model of the cosmos was indeed suggested by the followers of Pythagoras—Pythagoreans—in the fourth century BCE. The philosopher Philolaus proposed that the Earth, Sun, and planets all moved in circular orbits around a central fire. Greek philosopher Heraclides of Pontus added, also in the fourth century BCE, that the Earth rotated around its axis too, while Aristarchus of Samos was the first to propose a heliocentric model in the third century BCE.
In terms of its logical exposition, Foscarini’s book was outstanding. He explained that there was no doubt that Galileo’s discoveries made the Copernican system demonstrably much more plausible than the Ptolemaic one. Assuming that Copernican cosmology was correct, and taking for granted that Scripture always represented the truth, Foscarini argued that there clearly could be no conflict between them, since there is only one truth. He concluded therefore that it had to be possible to reconcile those seemingly problematic biblical passages with Copernicanism. This was precisely what Galileo had been claiming all along. Foscarini, by examining many of the contentious biblical paragraphs and grouping them into six categories, was able to offer specific exegetical principles that he thought could be used to eliminate all the apparent contradictions. Foscarini’s motivation for writing the book was also remarkable: if Copernicanism were proven to be correct in the future, he argued, the Church would be able to use his new interpretations of the controversial texts to escape the inadmissible verdict that the Bible is wrong.
In conclusion, Foscarini made two important observations. First, regarding the interpretation of the biblical language:
Scripture serves us by speaking in the vulgar and common manner; for from our point of view, it does seem that the earth stands firmly in the center and that the sun revolves around it, rather than the contrary. The same thing happens when people are carried in a small boat on the sea near the shore; to them it seems that the shore moves and is carried backwards, rather than that they move forwards, which is the truth.
Foscarini’s second significant point was quite astonishing in its boldness: “The Church,” he said, “cannot err, in matters of faith and our salvation only. But the Church can err in practical judgments, in philosophical speculations, and in other doctrines which do not involve or pertain to salvation.”
Cesi thought that Foscarini’s book “could not have appeared at a better time, unless to increase the fury of our adversaries is damaging, which I do not believe.” Galileo’s subsequent actions indicate that he believed the same, at least initially. Unfortunately, they were both wrong. Church official Giovanni Ciampoli, later the correspondence secretary of Pope Urban VIII and a member of the Lincean Academy, predicted in a letter he wrote to Galileo on March 21, 1615, that Foscarini’s book would be condemned by the Holy Office. (Ciampoli may have had some inside information.)
The first reaction to Foscarini’s book came in the form of the opinion of an unnamed theologian. In the first paragraph, he labeled Foscarini’s views on Copernicanism as “rash.” In his documented Defense, Foscarini vehemently rejected this characterization, stating forcefully again that there is a clear distinction between matters of faith and morals, and those related to natural philosophy and science. Concerning the latter, Foscarini repeated his position that “the Sacred Scriptures ought not to be interpreted otherwise than according to what human reason itself established from natural experience and according to what is clear from innumerable data.”
Foscarini sent a copy of the book and of his Defense to Cardinal Bellarmino for comment, and Bellarmino answered on April 12, 1615, emphasizing three points:
First, it seems to me that Your Paternity and Mr. Galileo are proceeding prudently by limiting yourselves to speaking suppositionally and not absolutely, as I have always believed that Copernicus spoke. For there is no danger in saying that by assuming the earth moves and the sun stands [the Copernican model], one saves all the appearances better than by postulating eccentrics and epicycles [the Ptolemaic model]; and that is sufficient for mathematicians.
This language clearly implied more a form of advice rather than praise, to both Foscarini and Galileo—even though Bellarmino’s letter wasn’t even addressed to Galileo.
“However,” the cardinal was quick to add, “it is different to want to affirm that in reality [emphasis added] the sun is at the center of the world and only turns on itself without moving from east to west, and the earth is in the third heaven [meaning the third orbit in terms of its distance from the Sun] and revolves with
great speed around the sun.” Bellarmino then explained why, in his view, claiming that the Copernican scenario represented reality was “a very dangerous thing.” This was, he said, since it was “likely not only to irritate all scholastic philosophers and theologians, but also to harm the Holy Faith by rendering Holy Scripture false.”
Bellarmino’s second point had to do with interpretations of the biblical texts. Here he started with something he regarded as obvious: “As you know, the Council [Trent] prohibits interpreting Scripture against the common consensus of the Holy Fathers.” Then, however, he delivered an exegetical bombshell. In response to Foscarini’s claim that the Holy Fathers’ authority in interpreting the Bible applies only to matters of faith and morals but not to topics such as the motion of the Earth, Bellarmino offered a startling expansion of what should be called “matters of faith”:
Nor can one reply that this [the motion of the Sun or the Earth] is not a matter of faith because of the subject matter, it is still a matter of faith because of the speaker [emphasis added]. Thus, anyone who would say that Abraham did not have two sons and Jacob twelve would be just as much a heretic as someone who would say that Christ was not born of a virgin, for the Holy Spirit has said both of these things through the mouth of the Prophets and the Apostles.
Simply put, Bellarmino contended that not only is everything said in Scripture true, but that everything, including the most banal factual detail (as long as its meaning is clear) is also a “matter of faith”! Clearly, under this much broader definition of “matters of faith” by the most influential cardinal of the day, even the Earth’s motion became a matter of faith.
Thirdly, Bellarmino admitted that “if there were a true demonstration that the sun is at the center of the world and the earth in the third heaven, and that the sun does not circle the earth but the earth circles the sun, then one would have to proceed with great care in explaining the Scriptures that appear contrary, and say rather that we do not understand them, than that what is demonstrated is false.” However, Bellarmino also proclaimed: “But I will not believe that there is such a demonstration until it is shown to me,” emphasizing that it would definitely not be sufficient “to demonstrate that by assuming the sun to be at the center and the earth in the heaven one can save the appearances.” To add further weight to this last statement, the cardinal went on to say that it was King Solomon “who not only spoke inspired by God, but was a man above all others wise and learned in the human sciences” who wrote in Ecclesiastes 1:5: “The sun also ariseth, and the sun goeth down, and hasteth to his place where he arose.” Consequently, Bellarmino concluded, it was highly unlikely that the Sun, in fact, did not move, especially since every scientist “experiences that the earth stands still” and sees “that the sun moves.”
Bellarmino’s answer to Foscarini has been scrutinized, analyzed, and interpreted by numerous Galileo scholars, and opinions on it span the entire range from high praise, claiming that Bellarmino had demonstrated the open-mindedness of a forward-thinking scientist who anticipated the relativism of later centuries, to complete dismissal, arguing that he exhibited conservative narrow-mindedness. We shall return to the theological points later, but for the moment, let’s concentrate more critically on Bellarmino’s scientific reasoning.
His opening statement appeared to be quite promising: “if there were a true demonstration that the sun is at the center… then one would have to proceed with great care in explaining the Scriptures.” In fact, had he finished with this passage, he would have exhibited an intuitive awareness of what was to become a guiding principle in science: when new observations contradict existing theories, the theories need to be reexamined. The problem was that he immediately followed that paragraph with text indicating that he believed such a demonstration to be eternally unachievable. Bellarmino gave a few reasons for this misguided conviction, all patently nonscientific. First, he stated that “saving the appearances” in astronomy did not constitute proof of the Earth’s motion. Even this seemingly convincing point went against genuine scientific thinking. If two different theories explain all the observed facts equally well, scientists would prefer to adopt, even if tentatively, the simpler one. Following Galileo’s discoveries, such a process would have definitely favored the Copernican system over the Ptolemaic one, which was what Galileo had been championing all along. The requirement of simplicity would have also given an advantage to Copernicanism over Tycho Brahe’s hybrid geocentric-heliocentric model. Of course, the ultimate test would have been to find direct proof for the Earth’s motion or for the two theories to make some predictions that could then be tested by subsequent observations or experiments. In contrast, Bellarmino preferred to stick with the theory favored by the Church’s orthodoxy.
The cardinal’s second argument had really nothing to do with science. It advocated a blind acceptance of authority: on one hand, through the adoption of the interpretation of the Holy Fathers, and on the other, relying on the presumed infinite wisdom of King Solomon, who supposedly had written the book of Ecclesiastes. Both of these reasonings were manifestations of an attitude that was completely foreign to the spirit of science and entirely antithetical to what Galileo was espousing. In other words, far from being a forward-thinking scientist, faith trumped science in Bellarmino’s world.
Finally, Bellarmino’s third remark represented a misunderstanding coupled with parochial thinking. He declared that we all experience that the Earth does not move, rather than recognizing that all we can say is that it appears to us not to move. To prove his point, and referring to the example given by Foscarini in his book, he claimed that “when someone moves away from the shore, although it appears to him that the shore is moving away from him, nevertheless he knows that this is an error and corrects it, seeing clearly that the ship moves and not the shore.”
Following ideas he inherited from Copernicus, Galileo could not accept this line of reasoning. In the same way that one couldn’t tell whether it was the Sun or the Earth that was moving, only that there was relative motion between them, he insisted that no experiment performed inside a sealed room moving at a constant speed along a straight line could tell whether you are standing still or moving. This insight is familiar to anybody who watches from a train window another train moving on a parallel track. It later became an essential pillar of Einstein’s theory of special relativity, in which he showed that the laws of physics are the same for all observers moving at a constant relative velocity. One can, of course, argue that Bellarmino could not have anticipated in the seventeenth century what Einstein would discover and prove centuries later, but Bellarmino’s position was extremely rigid. He did not believe that a proof of Copernicanism could ever be found. This was in stark contrast to what even Foscarini, a theologian himself, spelled out perspicuously: “Since something new is always being added to the human sciences, and since many things are seen with the passage of time to be false which previously were thought to be true, it could happen that, when the falsity of a philosophical opinion has been detected, the authority of the Scriptures would be destroyed.” That is to say, while Foscarini understood that new discoveries and the knowledge gained from science could render models prevailing at the time (and thereby biblical interpretations) false, Bellarmino hid behind a dogmatic assurance.
Galileo addressed some of the theological issues in detail in his Letter to the Grand Duchess Christina, but it is worth pointing out that Bellarmino’s letter to Foscarini contained ab initio a surprisingly weak argument even when it came to theology. This forced him to adopt something that we would refer to today as the “nuclear option.” Bellarmino relied on the “common consensus of the Holy Fathers” and on the decree by the Council of Trent. However, as both Galileo and Foscarini noted perceptively, the council’s pronouncement had specifically spoken about “matters of faith and morals, pertaining to the edification of Christian Doctrine,” while the Earth’s motion had nothing to do with faith or morals, nor had the Holy Fathers ever discusse
d or reached consensus on this topic. Apparently, even Bellarmino himself was aware of this shortcoming of his reasoning, since otherwise there is no convincing explanation for his amplification of the definition of “matters of faith” far beyond the usual religious issues, to include essentially everything in the Bible.
Galileo managed to see Bellarmino’s letter to Foscarini, and at one point, he even articulated a response in a series of notes that he may have intended to send to Foscarini. But those undated notes were never published. Galileo’s main point addressed Bellarmino’s new, sweeping definition of “matters of faith” with razor-sharp logic:
It is replied that then everything which is in Scripture is a “matter of faith because of who said it,” and thus in this respect ought to be included in the regulations of the Council [of Trent]. But this is clearly not the case, because then the Council ought to have said, “The interpretations of the Fathers must be followed for every word in the Scriptures,” rather than “in matters of faith and morals.” Thus having said “in matters of faith,” it seems that the Council’s intention was to mean “in matters of faith because of the subject matter.” It would be much more “a matter of faith” to hold that Abraham had sons, and that Tobias had a dog, because the Scriptures say so, than to hold that the earth does not move, granting that the latter is found in the Scriptures themselves. The reason why the denial of the former, but not of the latter, would be a heresy is the following. Since there are always men in the world who have two, four, six, or even no sons, and likewise since someone might or might not have dogs, it would be equally credible that someone has sons or dogs and that someone else does not. Hence there would be no reason or cause for the Holy Spirit to state in such propositions anything other than the truth, since the affirmative and the negative would be equally credible to all men. But this is not the case concerning the mobility of the earth and the stability of the sun, which are propositions far removed from the apprehension of the common man. As a result, it has pleased the Holy Spirit to accommodate the words of the Sacred Scripture to the capacities of the common man in such matters which do not concern his salvation, even though in nature the fact be otherwise.