Galileo Revisited

Andrew Schuman and Robert Cousins

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The uneasy coexistence between science and religion dates back hundreds of years. Throughout the centuries, the two traditions have clashed on numerous occasions, but none has received more attention than the conflict between Galileo Galilei and the Roman Catholic Church during the early seventeenth century. This confrontation has come to define the schism between science and religion. Indeed, Galileo now represents modern science’s fight to free itself from the shackles of organized religion, blind faith, and superstition. 1 In reality, however, Galileo was an ardent Catholic; he counted the Pope among his closest friends and considered heresy “more abhorrent than death itself.” 2 The pursuit of scientific knowledge, which was then called natural philosophic knowledge, was framed only in the context of religious speculation. How, then, did this pious man of learning become an icon for those who stand for the so-called incompatibility between science and religion?

Nicolas Copernicus published On the Revolutions of the Heavenly Spheres in 1543, twenty one years before Galileo’s birth. In this seminal work, Copernicus proposed the first mathematical model of a sun-centered cosmos. First posited in the fifth century B.C. by students of the Greek mathematician Pythagoras, the heliocentric model was largely ignored in favor of the geocentric—that is, Earth-centered—model supported by Aristotle and later Ptolemy. Copernicus readily admitted hesitancy about his counterintuitive hypothesis. “The newness and absurdity of my opinion almost drove me to abandon a work already undertaken.” 3 But he thought it even more absurd that a supremely rational God would create a world in which astronomical calculations were so difficult and confusing, writing:

I began to be annoyed that the philosophers had discovered no sure scheme for the movement of the machinery of the world, created for our sake by the most systematic Artist of all. 4
Copernicus believed not only that the world was inherently systematic—governed by immutable laws that stemmed from the rationality of the Godhead—but also capable of comprehension and explanation. It was for this reason that he, “Began to consider the mobility of the earth…even though the idea seemed absurd.” 5

Copernicus was, like many other natural philosophers of his day, a deeply religious man. He saw no conflict between knowledge attained through science and knowledge revealed through Scripture. Indeed, the inherent compatibility between science and religion as two paths to the same truth was a fundamental doctrine of the Roman Catholic Church. First enunciated by Augustine in the fourth century, this doctrine of the unity of truth sprang from the belief that, “There is no teacher of truth but God, no matter where it comes to light.” 6

Despite its radicalness, the heliocentric model did not incur official disapproval until long after Copernicus’ death. In fact, when Copernicus first presented his new system to Pope Clement VII in 1553, it was met with immediate praise. Impressed by the mathematical precision of the calculations based on the heliocentric premise, the Pope urged Copernicus to publish his work. He also requested that Copernicus use his new astronomy to revise the calendar, something that was urgently desired at the time. The Pope’s approval of the Copernican hypothesis was representative of its success elsewhere; people who understood Copernicus’ work considered it brilliant, and those who did not understand simply ignored the matter altogether.

The relatively small impact of this revolutionary hypothesis on the sixteenth century European mindset resulted from Copernicus’ lack of any supporting evidence for his theory. Copernicus may have believed his model to be more than a hypothesis, but he made no effort to convince the public of this. An anonymous introductory note to Revolutions declares that the model is not proposed to “convince anyone that [it is] true, but merely to provide a reliable basis for computation.” 7 Precise astrological predictions were considered to be the main goal of astronomy, so the hypothesis was accepted as a convenient fiction.

The hypothetical status of heliocentricity began to change at the start of the sixteenth century. In 1609, Galileo Galilei pointed his telescope to the heavens and began a series of discoveries that would lead him to an outright rejection of the Aristotelian-Ptolemaic view of the cosmos in favor of the Copernican model. Galileo’s use of the telescope transformed the cosmological debate from one that was decided by philosophy and mathematics to one that could be decided by direct observation. Armed with his experimental evidence, Galileo set out to convince everyone from peasants to the Pope that Copernicus had been right.

Although Galileo was not a Copernican in his early years, he had long harbored doubts about Aristotelian physics. Just as he offered telescopic observations in support of Copernicanism, Galileo based his critique of Aristotle on experimentation. In 1582, at the age of 18, Galileo began to experiment with the oscillatory motion of simple pendulums by tying a rock to the end of a string. Before long he had graduated to larger-scale undertakings including the famous—and possibly apocryphal—experiment in which he dropped two stones of different weights from the Leaning Tower of Pisa to prove that they fell at the same rate of acceleration. This cemented Galileo’s reputation as a willing challenger of Aristotelian physics and someone who was not reticent about sharing his views.

Galileo had long considered the Copernican system “much more probable than the view of Aristotle and Ptolemy,” 8 but it was only after his telescopic discoveries that Galileo fully embraced heliocentricity. In early 1610 Galileo published The Starry Messenger, a short booklet that presented his discoveries about the Earth-like surface of the moon and four previously unknown moons which were observed to orbit the planet Jupiter and not the earth. Both of these discoveries challenged Aristotelian cosmology, which maintained that the moon was a perfect spherical orb and that all orbits had the Earth at their center. The book was an immediate success, selling out in the first week of its release. Because The Starry Messenger was written in the Italian vernacular, Galileo’s discoveries spread quickly among the lower classes as well as the elite and won him instant fame. Within the year Galileo was appointed “Chief Mathematician and Philosopher” to the Grand Duke of Tuscany and elected to the prestigious Lyncean Academy in Rome.

Before long, however, opposition to Galileo’s theories began to arise. The first hint of the persecution that lay ahead came in December 1613 at a breakfast hosted by Grand Duchess Christina of Lorraine. Although Galileo was not present, his pupil and close friend Benedetto Castelli fielded the Grand Duchess’ questions about the implication of Copernicanism for the Bible. Christina quoted from the Book of Psalms: “O Lord my God, You are very great … He set the Earth on its foundations, so that it should never be moved.” 9 Castelli responded by saying that this passage, as well as the part of the Book of Joshua 10 that deals with God’s stopping the sun in the sky, was not intended to mean the Earth is literally stationary. This was apparently a satisfactory explanation; Castelli wrote to Galileo: “Madama remained against me, but from her manner I judged that she did this only to hear my replies.”11

Galileo was deeply troubled by Christina’s objections. He feared the episode foreshadowed a drawing of battle lines between science and Scripture. Galileo himself saw no conflict between the two; echoing the Augustinian theology of a unity of truth, he wrote:
Holy Scripture and Nature are both emanations from the divine word: the former dictated by the Holy Spirit, the latter the observant executrix of God’s commands . . . Scripture cannot err . . . [but] its expounders and interpreters are liable to err in many ways. 12
 Galileo drew primarily on the doctrine of accommodation to reconcile his experiments and observations to the Bible. Accommodation holds that Scripture was written with words and idioms that could be understood by the audience of the time in accordance with their common experience in order to aid their understanding of matters pertaining to salvation. 13 For instance, in the aforementioned passage from the Book of Joshua, writing that the earth stood still would have been incomprehensible to the readership, so the sun was recorded as having been stopped in the sky instead. Accommodation had been Roman Catholic orthodoxy since the time of Augustine, but as Thomas Aquinas wrote, “Scripture speaks according to the opinion of the people.” 14

In February of 1615, Niccolo Lorini, a Dominican friar, obtained a copy of one of Galileo’s widely circulated letters expounding his view of the heavens and of Scripture. Lorini was disturbed by what he read and immediately sent the letter to Rome to be reviewed by the Inquisition as possible heresy. He was chiefly concerned that Galileo’s interpretations of Scripture contradicted the church fathers. Not only that, Galileo’s training was not in theology but in mathematics and science. If any reinterpretation were called for it would be done by those qualified for the task—a council of theologians—and not a layman acting on his own. And although Galileo received mild censure from the Inquisition regarding the language of his letter, he was not officially punished.

Nevertheless, it was a difficult time for the Roman Catholic Church to face another call for revision and reform. Less than a century had passed since Martin Luther had posted his Ninety Five Theses on the door of the Wittenburg Cathedral, but already the Protestant Reformation was threatening Europe’s religious unity. One of the central conflicts revolved around who possessed the authority to interpret Scripture. The Protestant reformers insisted upon individual interpretation of the Bible, while Roman Catholic orthodoxy, reaffirmed by the Council of Trent, forbade any interpretation that disagreed with the “unanimous agreement of the Fathers.” 15 Not only that but the Thirty Years’ War, which was fought along religious lines, was in the offing. Even though hostilities had not yet commenced, conflicts of any kind of religious nature were greatly magnified.

Galileo was not the only one arguing for an open interpretation of Scripture in light of recent scientific and mathematical discoveries. Also in 1615, theologian Antonio Foscarini published a letter in which he too argued for the compatibility of Copernicanism with the Bible. Foscarini sent a copy of this letter to Cardinal Bellarmine, Master of Controversial Questions at the Roman College, asking for his feedback and advice; Bellarmine’s response provides an excellent framework for understanding the conflict between Galileo and the Roman Catholic Church.

Bellarmine opened his letter by praising Galileo and Foscarini for “proceeding prudently by limiting yourselves to speaking suppositionally and not absolutely, as I have always believed that Copernicus spoke.” 16 He thanked Galileo and Foscarini for affirming that Copernicanism was merely a hypothesis and not objective reality. In truth, however, the two scientists believed the opposite. Bellarmine further reminded them that the Council of Trent prohibited, “Interpreting Scripture against the common consensus of the Holy Fathers.” 17 Lastly, Bellarmine asserted, “If there were a true demonstration that the sun is at the center of the world…then one would have to proceed with great care in explaining the Scriptures that appear contrary. But I will not believe that there is such a demonstration, until it is shown to me.” 18

This letter shows that the fundamental conflict between Galileo and Bellarmine was straightforward. They did not disagree about the relationship between science and Scripture; both men believed there was only one truth and new scientific demonstrations necessitated a reinterpretation of the Bible. They differed only on the question of when reinterpretation was appropriate and who had the authority to do it. Galileo believed he had sufficient evidence to support Copernicanism, but Cardinal Bellarmine wasn’t satisfied. He knew the task of reinterpretation would be long and difficult, and there needed to be sufficient scientific evidence before the church authorities would consider revising established dogma.

The shortcoming in Galileo’s research was that he had not been able to prove that the Earth was not a stationary body. As rumors of heresy began to swirl, Galileo found himself increasingly pressed to resolve the matter. In a letter to Cardinal Dini, who was sympathetic to his position, Galileo wrote:
To me the surest and swiftest way to prove that the position of Copernicus is not contrary to Scripture would be to give a host of proofs…thus, since no two truths can contradict one another, this and the Bible must be perfectly harmonious. 19

Before long Galileo believed he had his proof. He put forth in a letter to Cardinal Alessandro Orsini that the earth’s diurnal motion on its axis caused the ebb and flow of the tides. This theory is now known to be incorrect, but to Galileo it made perfect sense; he envisioned the tides flowing much the way water sloshes around in a moving container. Fearing that the official condemnation of Copernicanism was near, Galileo headed to Rome in December of 1615 to clear his name from suspicion of heresy.

On February 19, 1616, the two primary tenets of the Copernican system—the Sun is stationary and the Earth moves—were submitted to the qualificators of the Holy Office for a vote. After a mere four days of discussion, both propositions were condemned as heretical, and Copernicanism was rejected as a portrayal of objective reality. The qualificators determined that both propositions were “foolish and absurd in philosophy . . . [and] formally heretical.” 20 Galileo himself was not named in the official announcement, although Foscarini’s work was condemned outright and Copernicus’ Revolutions was “suspended until corrected.” 21 In exchange for being spared public humiliation, Galileo was asked by Cardinal Bellarmine to abandon his belief that Copernicanism was more than a hypothesis and to refrain from publicly teaching or defending it. Offered his dignity and the freedom to continue observing the heavens in private, Galileo agreed to Bellarmine’s request.

Galileo honored the bargain and did not publish any work for the next seven years. However, in August of 1623, he received word that his long time friend and supporter Cardinal Barberini had been elected Pope. As Cardinal Bellarmine had passed away by this time, Galileo saw the opportunity to again advance the ideas of Copernicus in public. In April of 1624, Galileo left for Rome on the pretense of paying homage to Pope Urban VIII; during his time in Rome he was granted six private audiences with the Pontiff.

Galileo returned home to Florence with Urban’s blessing to write a book comparing the Copernican and Aristotelian models of the cosmos. Because Urban believed that the tides did not provide conclusive proof for Copernicanism and therefore the system should only be taken as a hypothesis, he included a caveat in his permission. The book—which would be formatted as a dialogue—had to include Urban’s own opinion that God, in His infinite power, could easily make the tides ebb and flow on a stationary Earth through means that only He understood. 22 Galileo readily agreed and immediately set to work.

The book, entitled A Dialogue on the Two Chief World Systems, is constructed as a discussion between three men, Salviati, Sagredo, and Simplicio. Salviati argues for the Copernican system and is Galileo’s mouthpiece, while his opponent, Simplicio, is an ignorant Aristotelian who is repeatedly outwitted. Sagredo claims to be an informed and neutral participant; he asks questions of both sides but usually sides with Salviati. The dialogue occurs over a four day period during which the Aristotelian system is methodically dismantled, while the evidence for Copernicanism swells.

Galileo presented his central argument, the use of the tides to prove the Earth’s motion, on the fourth day of the characters’ debate. Salviati lays out Galileo’s proof in great detail and only then, on the last page of the book, does the Pope’s opinion appear. Simplicio’s rebuttal to Salviati states:
God in His infinite power and wisdom could have conferred upon the watery element its observed reciprocating motion using some other means than moving its containing vessels. 23

Galileo’s decision to frame the Pope’s opinion in this way was, in the kindest interpretation, undiplomatic. Urban’s words came from the mouth of Simplicio, the babbling Aristotelian whose name is disparaging of his intellectual capacity and who was repeatedly insulted by the other men. Galileo could have given the Pope’s opinion to the more neutral Sagredo, but instead he chose to voice it from the mouth of the fool. What’s more, Galileo immediately cast aside this opposing view with Salviati’s biting reply: “What a lovely and angelic doctrine!” 24

When the Dialogue was published in 1632, the Pope was furious. He repeatedly told the Tuscan ambassador, “I have been deceived!” 25 Indeed, his feeling of betrayal is understandable. Urban had supported and protected Galileo in the 1616 controversy; he had given him permission to write the Dialogue, and he had even written a poem in his honor; yet all he received in return was embarrassment and insult. When whispers of heresy cropped up around Galileo’s book, the scientist found himself alienated from his most powerful ally. Indeed, Urban had completely turned against him, even leading the campaign to bring Galileo before the Holy Inquisition.

However, it was not only the insult that drove Urban to withdraw his support of his friend. Europe was embroiled in the Thirty Years’ War, and in 1632 things were going poorly for the Catholic states against their Protestant foes. Frustrated that Urban refused to commit the soldiers and funds under his command to the war effort, the King of Spain had noisily denounced the Pope as a weak leader and intimated that he might be in league with the Protestants. With this as a backdrop, Urban could ill afford to suffer any further humiliation, and the unfortunate state of affairs with Galileo provided him with an opportunity to prove his strength.

In January of 1633, Galileo received a knock on his door. Much to his surprise, he found the Florentine Inquisitor standing at his doorstep. The Inquisitor’s message was sober: Galileo was to leave immediately for Rome to stand trial before the Papal Inquisition. If he refused, he would be brought there “imprisoned and in chains.” 26

In the fall issue we will examine Galileo’s trial before the Inquisition, a clash that continues to influence how we view the relationship between science and religion even today.

1. William E. Carroll, “Galileo and the Inquisition.” Journal of Religion and Society, 1999 [journal on-line]; available from http://moses.creighton.edu/JRS.

2. Dava Sobel, Galileo’s Daughter (New York: Walker & Company, 1999) 60.

3. Ibid., 51.

4. Ibid., 50.

5. Ibid., 50.

6. Lawrence M. Principe, “Church, Copernicus, and Galileo.” Science and Religion Course No. 4691. Johns Hopkins University.

7. Caltech Alumnus Server, “What Science Is,” California Institute of Technology, http://alumnus.caltech.edu/~rbell/Science.html.

8. Sobel, 52.

9. Psalm 104:1, 5. The Holy Bible, English Standard Version, (Wheaton, Il.: Good News Publishers, 2002).

10. Joshua 10:13. ESV.

11. Sobel, 63.

12. Ibid., 63, 64.

13. Principe, “Church, Copernicus, and Galileo.”

14. Ibid.

15. Sobel, 72.

16. Annibale Fantoli, Galileo: For Copericanism and for the Church Vol. 3, trans. George V. Coyne S.J. (Italy: Vatican Observatory Publications, 1994) 174.

17. Ibid, 175.

18. Ibid..

19. Ibid., 179.

20. Ibid., 199

21. Ibid., 207.

22. Ibid., 299.

23. Ibid., 336.

24. Principe, “Church, Copernicus, and Galileo.”

25. Ibid.

26. Fantoli, 391.

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