The “Galileo affair” is perhaps the most commonly discussed case of conflict between science and religion. According to widespread popular belief, Galileo Galilei (1564-1642) was a martyr of science; that he was not only tortured, but imprisoned by the Roman Catholic Church. Although this myth may make for good drama, it is seriously deficient as history. As many contemporary historians of science have argued, including Maurice A. Finocchiaro in his article in Galileo goes to Jail, the Church had understandable reasons for refusing to accept Galileo’s heliocentric model of the solar system: Galileo was unable to produce the proof he needed; the waters were also muddied by Galileo’s academic enemies and by several misunderstandings, basic mistakes, missed opportunities, and complex theological debates that were rooted in the Protestant Reformation. Richard J. Blackwell argues that the Galileo affair is centered on four important issues:
(1) the state of the scientific debate at that time over the comparative merits of the older earth-centered astronomy of Claudius Ptolemy (second century AD) and the more recent but conflicting sun-centered theory of Copernicus (1473-1543)
(2) the historical events that led the Catholic Church in 1616 to condemn Copernicanism as false and their rationale
(3) the question of what are the proper exegetical standards to be used in understanding the meaning and the truth of the Bible
(4) and the charges, the legal ground, and the course of events in Galileo’s trial and condemnation in 1633.
The Historical Background
For nearly two thousand years before the Galileo affair, the almost universally accepted view of the heaven in Western culture was the geocentric theory initially proposed by Aristotle (384-322 BC) and later considerably refined mathematically by Ptolemy. Heliocentric systems were not unheard of, but they survived in Late Antiquity and the Middle Ages merely as curiosities. This universally accepted geocentric system, which came to permeate the medieval scientific and religious tradition, looked upon the earth as spherical, motionless, and fixed in the center of the entire universe. All of the then known observational evidence concerning the heavens was consistent with this astronomical model, especially when it was interpreted in the light of Aristotelian natural philosophy.
However, in 1543 Nicolaus Copernicus, a church official and accomplished astronomer from norther Poland, published a book, On the Revolutions of the Celestial Orbs, in which he took the heliocentric system and defended it as a true description of the universe. Copernicus modified the earlier view in a major way by locating the sun at the center of the universe and the earth and its moon in motion around the sun. Copernicus had no new evidence to justify his theory; rather, his primary motivation was that he though that his view had more internal coherence and greater explanatory power than Ptolemy’s.
Copernicus’ book was a highly technical astronomical text, dominated by detailed geometrical models for all of the planets. Because his book was highly technical, written for a small audience of mathematically proficient astronomers, it was little known and less read. Contrary to other myths, its publication created no public stir. But the book did secure an audience among astronomers, many of whom employed it for calculating planetary positions, while denying its claim to cosmological truth.
Why was this so? Because the evidence that could be marshaled in the mid-sixteenth century in support of the heliocentric model as physically true was not convincing. No observation, taken by itself, could prove the sun rested and the earth moved. Predictions using the heliocentric system were no more accurate than those offered by the geocentric. If the advantages of the heliocentric system was slim, its disadvantages was greater. First, putting the earth in motion represented a massive violation of everyday common sense. Second, removal of the earth from the center of the cosmos represented a destructive attack on Aristotle’s physics—which was the only comprehensive system of physics in existence—and therefore represented a serious violation of scientific common sense. Third, to put the earth in motion was to put it into the heavens, thereby destroying the dichotomy between the heavens and the earth, which served as a fundamental cosmological premise wherever Aristotelian philosophy prevailed for the previous two millennia. Thus those astronomers and natural philosophers who rejected heliocentrism did so not because of blind conservatism or religious intolerance, but because of their commitment to widely held scientific principles and theories. Copernicus had been talked into publishing his book by various friends, including ecclesiastical officials. He had dedicated the Revolutions to the pope. And almost nobody judged his ideas dangerous.
Another important historical element to consider is that, in Galileo’s day, Western European culture was undergoing some fundamental and disruptive changes. The Protestant Reformation and the ensuing Counter had occurred during the previous century. Echoes of the Great Schism of 1054, when the Eastern Orthodox Churches split from Western Christianity, frightened the church authorities in Rome as they witnessed much of norther Europe also breaking away from their control. The Catholic Church responded with the Council of Trent (1545-63). Its main effect on the Galileo affair was it declaration that no individual Christian should interpret the Scriptures contrary to the common agreement of the early fathers of the church or contrary to the views of the pope and the bishops, who alone have the power to interpret the Bible. A decree on the interpretation of Scripture that emerged from the council reads:
The Council decrees that, in matter of faith and morals…no one, relying on his own judgment and distorting the Sacred Scriptures according to his own conceptions, shall dare to interpret them contrary to that sense which Holy Mother Church, to whom it belongs to judge their true sense and meaning, has held and does hold, or even contrary to the unanimous agreement of the Fathers.
This emphatic statement was a repudiation of the Protestant notion that Scripture stands alone as the proper authority for Christian belief and practice, in no way dependent on church tradition. As a result the Catholic Church in the sixteenth century had become unusually defensive, especially in regard to theological and scriptural matters. This attitude still predominated at the time of the Galileo affair. Thus if Copernicus’ book had been published either a century earlier or a century later, the Galileo affair would probably not have happened. But, in fact, it was published in 1543, when the Reformation was in full bloom and the Counter Reformation was just beginning. Hence it was that by 1616 all of the actors and cultural forces were in place for the drama of the Galileo affair to begin.
Galileo and Heliocentrism
Galileo did not begin advocating Copernicanism until 1609. He was acquainted with Copernicus’ work and appreciated its novel and significant argument for the earth’s motion. But Galileo was also acutely aware of the considerable evidence against Copernicanism stemming from direct sense experience, astronomical observation, and traditional physics.
However, Galileo, in 1609, learned from his friend Paolo Sarpi that a Dutch lens grinder, Hans Lipperhy, had developed an optical instrument that made distant objects appear much closer to the observer. Galileo perfected the newly invented telescope, and in the next few years made a series of important astronomical discoveries: that the surface of the moon contains many craters and mountains (contrary to Aristotle’s notion that the moon’s surface is a perfectly smooth sphere); that Jupiter has four moons that are invisible to the naked eye; that the surface of the sun displays continually changing dark spots that drift from left to right, which indicate that the sun is changeable and that it rotates on its own axis; and that Venus undergoes changing phases, like the moon, which proves that it revolves around the sun and not the earth (again contrary to Aristotle).
The Starry Messenger and Letters on Sunspots
Galileo’s publication of these and other observations brought him instant fame and controversy. He would describe all of these observations in his Starry Messenger (1610) and Letters on Sunspots (1613). Galileo’s telescopic observations certainly did not demonstrate the truth of the heliocentric model. However, they did, when deployed in his arguments, undermine some of the more powerful objections against heliocentric cosmology—a far cry from proving that heliocentric cosmology is true.
Nevertheless, in 1611 Galileo made a visit to Rome to plead the case for his telescopic discoveries in person. The Jesuits at the Collegio Romano confirmed his observations (but not the heliocentric interpretation that he gave them) and treated him as a celebrity.
Letters to Castelli and the Duchess Christina
But Galileo was not satisfied. Returning to Florence, Galileo attempted to further press his case for heliocentrism. In 1613 the religious orthodoxy of his pro-Copernican views first came under question at a social event at the ducal palace. Galileo responded in a pithy statement, addressed in the form of a letter to his disciple Benedetto Castelli, and in 1615 to the grand duchess dowager Christina. In his Letter to Castelli, Galileo explained his views on how the findings of natural philosophy should be related to Scripture. Galileo argued that the sole purpose of Scripture was to persuade readers “of those articles and propositions which are necessary for salvation” and that they “surpass all human reason.” When the scriptural passages oversteps those limits, addressing matters that are within reach of sensory experience and rational knowledge, God does not expect these God-given capacities to be abandoned. Thus theologians, before committing themselves to an interpretation of such passages, would be well advised to examine the demonstrative arguments of natural philosophers.
The Letter to Castelli was soon widely circulating. In 1615, Galileo considerably expanded his views into a much longer Letter to the Grand Duchess Christina. Some form of either letter eventually made it into the hand of a Dominican friar, and who quickly filed a written complaint against Galileo with the Inquisition in Rome. Although Galileo was never officially summoned to Rome, in December 1615 he decided to visit Rome of his own accord to defend the Copernican theory. He was so convinced that he had decisive arguments, he naively supposed that such arguments would carry him to victory over the geocentric opposition. A certain Antonio Querengo has left a vivid account of Galileo’s persuasive efforts:
He discourses often amid fifteen or twenty guests who make hot assaults upon him, now in one house, now in another. But he is so well prepared that he laughs them off; and although the novelty of his opinion leaves people unpersuaded, yet he reveals the futility of most of the arguments with which his opponents try to defeat him. Monday…in the house of Federico Ghislieri, he achieved wonderful feats; and what I liked most was that, before answering the opposing arguments, he amplified and strengthened them with new grounds that appeared invincible, so that, in subsequently demolishing them, he made his opponents look all the more ridiculous.
The Florentine ambassador to Rome, whose obligation it was to protect Galileo, was not pleased. Reporting to the grand duke of Tuscany, he wrote that Galileo “is vehement and stubborn and very worked up in this matter; and it is impossible, when he is around, to escape from his hands.” Galileo’s arrogant, impetuous style seems, on balance, to have been more effective in stirring up trouble and making enemies than in calming waters. Galileo received plenty of attention in Rome, but he did not convince the people who counted.
The entire issue reached a climax in the early months of 1616. In Februuary, Pope Paul V requested the opinion of a group of this theologians on the orthodoxy of heliocentrism. They advised him unanimously that Copernicanism was not only false but also formally heretical. The pope agreed with his theologians and publicly announced to the whole church in a decree issued by the Congregation of the Index, dated March 5, 1616, that Copernicanism was condemned as “false and completely constrary to Divine Scripture.” Copernicus’ Revolutions was on the Index of prohibited books. Although the Inquisition censured heliocentrism, Galileo faced no personal danger. He was charged with no offense; he was not declared a heretic. He was simply summoned by Cardinal Roberto Bellarmino, and informed him that heliocentrism had been declared false and heretical and was not to be held or defended. Galileo agreed and complied.
The decree of 1616 brought Galileo’s public campaign on behalf of Copernicanism to a halt. Toward the end of 1618 three comets passed through the European skies, causing excitement and eliciting a considerable amount of discussion on the nature of comets. Galileo joined in, but was once again drawn into controversy with a Jesuit mathematics professor, Orazio Grassi, who had written on the subject. The two were soon attacking each other. The controversy culminated in Galileo’s publication of a treatise, The Assayer (1623), where he bitterly attacked Grassi, pouring invectives upon invectives, accusing him of rude behavior, fraud, and intellectual theft. This text essentially poisioned the waters between Galileo and the Jesuits, with whom Galileo had managed, until now, to maintain friendly relations.
The Dialogue Concerning the Two Chief World Systems
In 1623, Cardinal Maffeo Barberini ascended the papal throne as Pope Urban VIII. Urban was considered an intellectual, a man of vision, and a moderate on the subject of heliocentrisim. Moreover, he was not only a fellow Tuscan, but an admiring personal acquaintance of Galileo. Before ascending the papacy, Urban had written a poem honoring Galileo for some of his telescopic discoveries; and just six weeks before his election, Urban had sent a letter to Galileo assuring him “that you will find in me a very ready disposition to serve you out of respect for what you so merit and for the gratitude I owe you.”
Thus with Urban now pope, Galileo felt freer to discuss heliocentrism. He requested an audience with the pope. In the course of six meetings, the two got around to the subject of cosmology. Urban made clear his belief that humans were, in principle, incapable of achieving certainty regarding cosmological matters. Nonetheless, from these meetings Galileo came to understand that he was free to write about heliocentrism, so long as he treated it as a mere hypothesis.
Galileo set to work, completing his Dialogue Concerning the Two Chief World Systems in 1629, which featured three characters engaged in a critical discussion of the cosmological, astronomical, physical, and philosophical aspects of Copernicanism but avoiding the biblical or theological ones. One spokesman, Salviati, vigorously presented the new ideas; another, Simplicio, argued doggedly and in detail for the old tradition; and the third, Sagredo, was the open-minded inquirer who critically assessed the issues from a neutral point of view. At the close of four days of dialogue, after bombarding his readers with arguments in favor of heliocentrism, Galileo had Simplicio essentially repeat much of Urban’s argument to him during their earlier meeting. That Galileo put it into the mouth of a slow-witted Aristotelian laughingstock of the dialogue did not escape Urban’s notice when the Dialogue finally became available in 1632, creating a sensation.
The Trial: Tortured and Imprisoned?
Galileo’s enemies inevitably complained that the book defended heliocentrism and so violated Bellarmino’s warning. What’s more, a new charge emerged: that Galileo violated a special injunction issued in 1616, prohibiting him from discussing the earth’s motion in any way whatever. Thus he was summoned to Rome for trial, which began in April 1633.
During the first hearing Galileo admitted receiving from Bellarmino the warning that heliocentrism could not be held or defended. But he denied receiving any special injunction not to discuss the topic in any way whatever. In his defense he introduced a certificate he had obtained from Bellarmino in 1616, which mentioned only the prohibition to hold or defend.
In light of Bellarmino’s certificate, the Inquisition’s officials tried out-of-court plea-bargaining: they promised not to press the most serious charge if Galileo would plead guilty to a lesser charge, that is, a transgression of the warning not to defend heliocentrism. Galileo agreed.
The trial ended on June 22, 1633. The Inquisition found Galileo guilty of “vehement suspicion of heresy.” He was forced to recite an abjuration retracting these beliefs. There is an extant lengthy sentencing document recounting the proceedings since 1613, summarizing the 1633 charges, and noting Galileo defense and confession. This text was, interestingly enough, publicized by the Holy Office. This unprecedented publicity resulted from the express orders of Pope Urban VIII, who wanted Galileo’s case to serve as a lesson to all Catholics.
The impression that Galileo may have been imprisoned and tortured is primarily found in these documents. Yet there new evidence surfaced in 1774 about the imprisonment from a correspondence in 1633 between Tuscan ambassador to Rome, Francesco Niccolini and Tuscan secretary of state in Florence, and secondarily that to and from Galileo himself. Galileo was important to these Tuscan officials because he was employed as the chief mathematician and philosopher to the grand duke of Tuscany.
Finocchiaro provides a helpful summary, and it is worth quoting him at length:
Galileo, having been summoned by the Inquisition, left Florence on January 20 and arrived in Rome February 13. The Inquisition allowed him to lodge at the Tuscan embassy on condition that he remain in seclusion until the proceedings started. On April 12 Galileo went to the Inquisition palace for his first interrogation. He stayed there for the next eighteen days while undergoing further interrogations, but he was put up in the prosecutor’s six-room apartment, together with a servant, who brought him meals twice a day from the Tuscan embassy. On April 30, after his second deposition was recorded and signed, Galileo returned to the embassy, where he remained for fifty-one days, interrupted by a visit to the Inquisition palace on May 10 to give a third deposition. On June 20, he was summoned to appear in court the following day. The next day he underwent “rigorous examination”—and remained at the Inquisition palace until the evening of June 24. It is unclear whether he was held in a prison cell or permitted to use the prosecutor’s apartment. On June 22 he appeared at the convent of Santa Maria sopra Minerva for sentencing and abjuration. Two days later Galileo moved from the Inquisition palace to Villa Medici in Rome, a sumptuous palace owned by the grand duke of Tuscany. On June 30 the pope granted Galileo permission to travel to Siena to live under house arrest at the residence of the archbishop, a good friend of Galileo’s. The archbishop hosted him for five months. In December 1633 Galileo returned to his own villa in Acreti, near Florence, where he remained under house arrest until his death in 1642.
Finocchiaro argues that with the possible exception of three days, Galileo was never held in prison, either during the trial or afterward. Even for those three days he likely lodged in the prosecutor’s apartment, not in a cell. The disposition, moreover, leaves no doubt that Galileo may have been threatened with torture during the June 21 interrogation, but there is no evidence that he was actually tortured, or that his accusers planned actually to torture him.
According to Finocchiaro, in view of all the available evidence, the most tenable position is that Galileo underwent an interrogation with the threat of torture but did not undergo actual torture. Although he remained under house arrest during the 1633 trial and for the subsequent nine years of his life, he never went to prison.
There are important lessons to learn from the Galileo affair, but not the ones customarily drawn. First, the Galileo affair had an enormous human and political dimension. As Lindberg put it, “there were old scores to settle, egos to stroke, and careers to be made.” Galileo’s own personality was undeniably a consistent and important factor: if he had played his cards differently, with more attention to diplomacy, Galileo might well have carried out a significant campaign on behalf of heliocentrism without condemnation.
Second, the outcome of the Galileo affair was powerfully influenced by local circumstances. We need to understand the tense circumstances then prevailing Rome. Europe was mid-way through the Thirty Years’ War; the power of the papacy was threatened by the Spanish, who controlled half of the Italian peninsular; and the pope himself had recently come under heavy criticism for adopting positions of political expediency apparently favorable to the Protestant king Gustavus Adolphus (1594-1632) of Sweden. At the local level, there were fears, rivalries, ambitions, personalities, political context, and socioeconomic circumstances.
And finally, everyone of the combatants, whether church official or disciple of Galileo, called himself a Christian; and all, without exception, acknowledged the authority of Scripture.