Part I Historical Episodes

The Copernican Revolution and the Galileo Affair

MAURICE A. FINOCCHIARO

The condemnation of Galileo Galilei (1564–1642) by the Inquisition in 1633 is perhaps the most significant episode in the long history of the interaction between science and Christianity. One reason is that the trial’s key intellectual issue (whether the earth is a planet revolving around the sun) was identical to the key issue of what is clearly the most important episode in the history of science – the Copernican Revolution. Another reason is that the victim happened to make numerous and epoch-making contributions to physics and astronomy, so much so that he is often called the father of modern science. A third reason is that the 1633 condemnation was a cause célèbre that continues to be a defining moment of modern Western culture. Thus, to understand this significance we need to delve into the Copernican Revolution, the Inquisition trial proceedings, and the key points of the subsequent affair.

The Copernican Controversy

In 1543, Nicolaus Copernicus (1473–1543) published his epoch-making On the Revolutions of the Heavenly Spheres (Copernicus 1992). In it, he updated an idea originally advanced by the Pythagoreans and Aristarchus in ancient Greece, but almost universally rejected: the earth moves by rotating on its own axis daily and revolving around the sun once a year. This contradicted the traditional belief that the earth was standing still at the center of the universe, with all heavenly bodies revolving around it. In its essentials, this geokinetic idea turned out to be true, as we know today beyond any reasonable doubt, after five centuries of accumulating evidence. At the time, however, the situation was different (Kuhn 1957; Finocchiaro 2010, 21–36).

Copernicus’s accomplishment was a new argument supporting an old idea: he demonstrated in quantitative detail that the known facts about the motions of the heavenly bodies could be explained more simply and coherently if the sun rather than the earth is assumed to be motionless at the center, and the earth is taken to be the third planet circling the sun. For example, from the viewpoint of simplicity, there are thousands fewer moving parts in the Copernican system than in the geostatic system, since the apparent daily westward motion of all heavenly bodies around the earth is explained by the earth’s daily eastward axial rotation, and thus there is only one body rotating daily, not thousands. Regarding explanatory coherence, this concept means the ability to explain many details of the observed phenomena by means of one’s basic principles, without adding ad hoc assumptions. Copernicus could thus coherently explain the periodic changes in the brightness and direction of motion of the planets, whereas the geostatic explanations of these details were improvised piecemeal.

However, Copernicus’s argument was a hypothetical one. That is, it was based on the claim that if the earth were in motion then the observed phenomena would result; but from this it does not follow necessarily that the earth is in motion. This claim does provide a reason for preferring the geokinetic idea, but it is not a decisive reason. It would be decisive only in the absence of contrary reasons. In short, one has to look at counterarguments, and there were many.

Some of them were mechanical, namely based on physics – the science of motion. For example, according to traditional Aristotelian physics, if the earth moved then terrestrial bodies would have to move in ways that do not correspond to how they are known (and easily observed) to move: freely falling bodies could not fall vertically, but would be left behind slanting westward; westward gunshots would range farther than eastward ones, instead of ranging equally; and loose bodies not firmly attached to the ground would fly off toward the sky. There is no way of escaping these mechanical consequences unless one rejects Aristotelian physics. To reject it effectively one must put something else in its place. This in turn involves building a new physics – something easier said than done. To put it briefly, Copernicus’s astronomy contradicted the physics of the time; the motion of the earth seemed to be a physical impossibility.

The idea was also considered to be a philosophical absurdity. For Copernicus did not claim that he could feel, see, or otherwise perceive the earth’s motion. Like everyone else, his senses (eyes and kinesthetic awareness) told him that the earth is at rest. Thus, some people objected that if his theory were true, then the human senses would be lying to us, and it was regarded as absurd that the senses should deceive us about such a basic phenomenon as the state of the terrestrial globe on which we live. That is, the geokinetic theory seemed to be in flat contradiction with direct sense experience, and so to violate the fundamental epistemological principle claiming that under normal conditions the senses provide us with an access to reality.

The Copernican theory also faced empirical difficulties in astronomy. That is, it had observational consequences regarding the heavenly bodies that were not in fact observed. For example, it implied that the earth (being a planet) should share various physical properties with the other planets; that the planet Venus should show periodic phases similar to those of the moon; that the planet Mars should show periodic changes in apparent size and brightness of a factor of about 60; and that the fixed stars should exhibit an annual shift in apparent position.

Finally, the geokinetic theory faced religious or theological difficulties. One objection was that the earth’s motion contradicted many biblical passages, which state or imply that the earth stands still. For example, Joshua 10:12–13 speaks of the miracle of stopping the sun: “On the day when the Lord gave the Amorites over to the Israelites, Joshua spoke to the Lord; and he said in the sight of Israel, ‘Sun stand still at Gibeon, and Moon, in the valley of Aijalon.’ And the sun stood still, and the moon stopped, until the nation took vengeance on their enemies.” Other anti-Copernican passages were Ecclesiastes 1:5 and Psalm 104:5.

In Catholic circles, this biblical objection was supplemented by one appealing to the consensus of Church Fathers – the saints, theologians, and churchmen who had played a formative role in the establishment of Christianity. The argument claimed that all Church Fathers were unanimous in interpreting relevant biblical passages in accordance with the geostatic view; therefore, the geostatic system is binding on all believers, and to claim otherwise is erroneous or heretical.

A third religious objection was more theological-sounding, based on the belief in the omnipotence of God: since God is all-powerful, he could have created any one of a number of worlds, for example one in which the earth is motionless; therefore, regardless of how much evidence there is supporting the earth’s motion, we can never assert that this must be so, for that would be to limit God’s power to do otherwise.

Regarding the religious objections, it is important to note two things. On the one hand, they were only part of the opposition to Copernicanism, since there were also the mechanical objections, the astronomical counterevidence, and the epistemological argument. On the other hand, religious criticism of Copernicanism was immediate, indeed it even antedated the publication of the Revolutions; it did not have to wait for Galileo, as often alleged.¹

Copernicus (1992, 3–50) knew that his hypothesis faced such difficulties. He realized that his novel argument did not conclusively prove the earth’s motion, and that there were many counterarguments of apparently greater strength. He was also aware of the religious objections. I believe these were the reasons why he delayed publication of his book until he was near death, although his motivation was complex and is not yet completely understood and continues to be the subject of serious research.

However, Copernicus’s argument was so important that it could not be ignored, and various attempts were made to come to terms with it, to assimilate it, to amplify it, or to defend it. Some thinkers (especially a group centered on the German University of Wittenberg) tried to exploit the mathematical advantages of Copernicanism without committing themselves to its cosmological claims, by adopting an instrumentalist interpretation according to which the earth’s motion was just a convenient instrument for making mathematical calculations and astronomical predictions, and not a description of physical reality (Westman 1975). Tycho Brahe (1546–1601) undertook an unprecedented effort to systematically collect new observational data, and he also devised another compromise, a theory that was partly heliocentric and partly geocentric, although fully geostatic: the planets revolved around the sun, but the sun moved daily and annually around the motionless central earth (Mosley 2007). Giordano Bruno (1548–1600), an Italian Dominican friar turned apostate, undertook a multi-faceted defense of Copernicanism that addressed epistemological, metaphysical, theological, and empirical issues; but Bruno’s defense remained largely unknown, disregarded, or unappreciated (Bruno 1995). Johannes Kepler (1571–1630) accepted Copernicanism for metaphysical reasons and then undertook a research program to prove its empirical adequacy, by meticulously analyzing Tycho’s data; the result was an improvement such that the planets revolved around the sun in elliptical, rather than circular, orbits (Kepler 1992).

The Trial of Galileo

The most significant response to the Copernican controversy was Galileo’s. He was born in Pisa in 1564, became professor of mathematics at the university there in 1589, and then taught at the University of Padua from 1592 to 1610.

During this period, Galileo researched primarily the nature of motion. He was critical of Aristotelian physics; favorably inclined toward Archimedean statics and mathematics; and innovatively experimental, insofar as he pioneered the procedure of actively intervening into and manipulating natural phenomena, combining empirical observation with quantitative mathematization and conceptual theorizing. Following this approach he formulated, justified, and systematized various mechanical principles: an approximation to the law of inertia; the composition of motion; the laws that in free fall the distance fallen increases as the square of the time elapsed and the velocity acquired is directly proportional to the time; and the parabolic path of projectiles. However, he did not publish these results during that period; indeed he did not publish a systematic account of them until 1638, in Two New Sciences (Galilei 1974; 2008, 295–367).

A key reason for this delay was that in 1609 Galileo became actively involved in astronomy. He was already acquainted with Copernicanism and appreciative of the fact that Copernicus had advanced a novel argument. Galileo also had intuited that the geokinetic theory was generally more consistent with his new physics than was the geostatic theory; in particular, he had been attracted to Copernicanism because he felt the earth’s motion could best explain why the tides occur. But he had not published or articulated this general intuition and this particular feeling. Moreover, he was acutely aware of the strength of the observational astronomical evidence against Copernicanism. Thus, until 1609 Galileo judged that the anti-Copernican arguments outweighed the pro-Copernican ones.

However, his telescopic discoveries led Galileo to a major reassessment. In 1609, he perfected the telescope to such an extent as to make it an astronomically useful instrument that could not be duplicated by others for some time. By its means he made several startling discoveries, which he published the following year in The Sidereal Messenger (Galilei 2008, 45–84): the moon’s surface is full of mountains and valleys; innumerable other stars exist besides those visible with the naked eye; the Milky Way and the nebulas are dense collections of large numbers of individual stars; and the planet Jupiter has four moons revolving around it at different distances and with different periods. As a result, Galileo became a celebrity, resigned his professorship at Padua, was appointed philosopher and chief mathematician to the grand duke of Tuscany, and moved to Florence the same year. Soon afterwards, he also discovered the phases of Venus and sunspots; on the latter, in 1613 he published the History and Demonstrations Concerning Sunspots (Galilei and Scheiner 2010; Galilei 2008, 97–102).

Although most of these discoveries were made independently by others, no one understood their significance like Galileo. The reason for this was threefold. Methodologically, the telescope implied a revolution in astronomy insofar at it was a new instrument for the gathering of a new kind of data transcending the previous reliance on naked-eye observation. Substantively, those discoveries strengthened the case for Copernicanism by refuting almost all empirical astronomical objections and providing new supporting observational evidence. Finally, this reinforcement was not equivalent to settling the issue because there was still some astronomical counterevidence (mainly, the lack of annual stellar parallax); because the mechanical objections had not yet been answered and the physics of a moving earth had not yet been explicitly articulated, although it was implicit in the research he had already accomplished; and because the theological objections had not yet been refuted. Thus, Galileo conceived a work that would discuss all aspects of the question. But this synthesis of Galileo’s astronomy, physics, and methodology was not published until 1632, in Dialogue on the Two Chief World Systems, Ptolemaic and Copernican (Galilei 2001; 2008, 190–271).

This particular delay was due to the fact that the theological aspect of the question got Galileo into trouble with the Inquisition, acquiring a life of its own that drastically changed his existence (Fantoli 2003; Finocchiaro 1989). For as it became known that he was convinced that the new telescopic evidence rendered the geokinetic theory a serious contender for real physical truth, he came increasingly under attack from conservative philosophers and clergy. They argued that Galileo was a heretic because he believed in the earth’s motion, which contradicted Scripture. Although he was aware of the potentially explosive nature of this issue, he felt he could not remain silent, but decided to refute the biblical argument. To avoid scandalous publicity, he wrote his criticism in the form of long private letters, in December 1613 to his disciple Benedetto Castelli, and in spring 1615 to the Dowager Grand Duchess Christina.

Galileo’s letters circulated widely and the conservatives got even more upset. Thus in early 1615, a Dominican friar filed a written complaint against Galileo with the Inquisition in Rome, and another Dominican made a formal deposition in person against him. An investigation was launched lasting about a year. As part of this inquiry, a committee of Inquisition consultants reported that the key Copernican theses were absurd or false in natural philosophy and heretical or erroneous in theology. The Inquisition also interrogated other witnesses. Galileo himself was not summoned or interrogated partly because the key witnesses exonerated him; partly because his letters had not been published, whereas his published writings contained neither a categorical assertion of Copernicanism nor a denial of the scientific authority of Scripture; and partly because he enjoyed the respect, trust, and protection of many high Church officials and powerful laymen.

However, in December 1615 Galileo went to Rome of his own accord to defend Copernicanism. He was able to talk to many influential officials and was received in a friendly manner; and he may be credited with having prevented the worst, insofar as the Inquisition did not issue a formal condemnation of Copernicanism as a heresy. However, he was otherwise unsuccessful. For in February 1616, he was privately given a personal warning by Cardinal Robert Bellarmine (in the name of the Inquisition), forbidding him to hold or defend the truth of the earth’s motion; Galileo agreed to comply. And in March, the Congregation of the Index (the department in charge of book censorship) published a decree which, without mentioning Galileo, did three things: it declared that the earth’s motion was physically false and contradicted Scripture; it condemned and permanently banned a book published by a clergyman in 1615 defending the earth’s motion from the scriptural objection; and it temporarily and partially banned Copernicus’s Revolutions, until and unless appropriately revised. Published in 1620, these revisions amounted to rewording or deleting a dozen passages suggesting that the earth’s motion was or could be physically true, so that the revised work would clearly convey the impression that geokineticism was merely a convenient hypothesis to make mathematical calculations and observational predictions.

For the next several years, Galileo kept quiet regarding the earth’s motion, until 1623, when Cardinal Maffeo Barberini became Pope Urban VIII. Since Barberini was an old admirer, Galileo felt freer and decided to write the book on the system of the world conceived earlier, adapting it to the new restrictions. He wrote the book in the form of a dialogue for three characters engaged in a critical discussion of all the arguments, except for the theological ones. This Dialogue was published in 1632 and its key thesis is that the arguments favoring the geokinetic theory are stronger that those favoring the geostatic view, and in that sense Copernicanism is more probable than geostaticism. When so formulated, the thesis is successfully established in the book. In the process, Galileo incorporated into the discussion the new telescopic discoveries, his conclusions about the physics of moving bodies, a geokinetic explanation of the tides, and various methodological reflections. From the viewpoint of the ecclesiastical restrictions, he must have felt that the book did not “hold” the theory of the earth’s motion because it was not claiming that the geokinetic arguments were conclusive; that it was not “defending” geokineticism because it was merely a critical examination of the arguments on both sides; and that it was a hypothetical discussion because the earth’s motion was being presented as a conjecture postulated to explain observed phenomena.

However, Galileo’s enemies complained that the book did not treat the earth’s motion as a hypothesis (in the instrumentalist sense) but as a real possibility, and that it defended the earth’s motion. These features allegedly amounted to transgressions of Bellarmine’s warning and the Index’s decree. And there was a third charge: the book violated a special injunction issued personally to Galileo in 1616 prohibiting him from discussing the earth’s motion in any way whatever; a document describing this injunction had been found in the file of the earlier Inquisition proceedings. Thus he was summoned to Rome to stand trial, which after various delays began in April 1633.

At the first hearing, Galileo was asked about the events of 1616. He admitted receiving from Bellarmine the warning that the earth’s motion could not be held or defended as true, but only discussed hypothetically. He denied receiving a special injunction not to discuss the topic in any way whatever, and in his defense he introduced a certificate he had obtained from Bellarmine in 1616, which mentioned only the prohibition against holding or defending. Here it should be mentioned that the Inquisition files did not contain a signed document recording the special injunction, but merely a clerk’s annotation to that effect. In the deposition, Galileo also claimed that the book did not really defend the earth’s motion, but rather suggested that the favorable arguments were inconclusive, and so did not violate even Bellarmine’s warning.

The special injunction must have surprised Galileo as much as Bellarmine’s certificate must have surprised the Inquisitors. Thus it took three weeks before they decided on the next step. The Inquisitors opted for out-of-court plea-bargaining: they would not press the most serious charge (violation of the special injunction), but Galileo would have to plead guilty to a lesser charge (unintentional transgression of the warning not to defend Copernicanism). He requested a few days to devise a dignified way of pleading guilty to the lesser charge. Thus, at later hearings, he stated that he had reread his book and was surprised to find that it gave readers the impression that the author was defending the earth’s motion, even though this had not been his intention. He attributed his error to wanting to appear clever by making the weaker side look stronger. He was sorry and ready to make amends.

The trial ended on 22 June, 1633 with a harsher sentence than Galileo had been led to believe. The verdict found him guilty of a category of heresy intermediate between the most and the least serious, called “vehement suspicion of heresy”; the objectionable beliefs were the cosmological thesis that the earth moves and the methodological principle that the Bible is not a scientific authority. He was forced to recite a humiliating “abjuration.” The Dialogue was banned. And he was condemned to house arrest indefinitely. In such a state, he died in 1642.

The Subsequent Galileo Affair

Although the 1633 condemnation ended the original affair, it also started a new controversy continuing to our own day – about the facts, causes, issues, and implications of the trial. This subsequent controversy partly reflects the original issues, but it has also acquired a life of its own, with debates over whether Galileo’s condemnation was right; why he was condemned; whether science and religion are incompatible; and so forth. The original affair is co-extensive with Galileo’s trials from 1615 to 1633; that is, it is the aspect of the Copernican Revolution consisting of Galileo’s contributions to it. The subsequent affair is much more complex because of the longer historical span, the broader interdisciplinary relevance, the greater international and multi-linguistic involvement, and the ongoing cultural import. Simplifying, its highlights are as follows (Finocchiaro 2005).

One strand of this story involved the key scientific claim for which he was condemned, namely the proposition that the earth moves. The condemnation ignited a scientific controversy, which had existed since Copernicus, but which now took a more definite and intense form – more definite because it now focused on whether the earth really moves and whether this motion can be proved experimentally by terrestrial or astronomical evidence, and more intense because scores of books were published, new experiments devised, new arguments invented, and old arguments rehashed.

In 1687, Isaac Newton (1642–1727) brought the Copernican Revolution to a climax with a synthesis and extension of the work of Copernicus, Kepler, Galileo, and others, in a book entitled Mathematical Principles of Natural Philosophy (Newton 1999). The Newtonian system has two important geokinetic consequences. First, the relative motion between the earth and the sun corresponds to the actual motion of both bodies around their common center of mass; but the relative masses of the sun and the earth are such that the center of mass of this two-body system is a point inside the sun; so, although both bodies are moving around that point, the earth is circling the body of the sun. Second, the daily axial rotation of the earth has the centrifugal effect that terrestrial bodies weigh less at lower latitudes and least at the Equator, and the whole earth is bulged at the equator and flattened at the poles; these consequences were verified by observation.

However, the controversy over the earth’s motion did not end then, because the Newtonian proofs were indirect. The search for direct evidence of the earth’s motion continued. This led to the discovery of the aberration of starlight by James Bradley in 1729, showing that the earth has translational motion in space; the discovery by Giambattista Guglielmini in 1789–1792 that freely falling bodies are deflected eastward away from the vertical by a small amount, confirming terrestrial axial rotation; the discovery of annual stellar parallax by Friedrich Bessel in 1838, proving the earth’s revolution in a closed orbit; and the invention of Foucault’s pendulum in 1851, providing a spectacular demonstration of terrestrial rotation.

Another strand of the subsequent affair involves actions by the Catholic Church to repeal the censures against the Copernican doctrine and books. In 1744, Galileo’s Dialogue was republished for the first time with the Church’s approval, as the fourth volume of his collected works; the text was preceded by the Inquisition’s sentence and Galileo’s abjuration of 1633 and by an introduction written by a contemporary biblical scholar. In 1757, at the request of Pope Benedict XIV, the Congregation of the Index dropped from the forthcoming edition of the Index of Prohibited Books the clause “all books teaching the earth’s motion and the sun’s immobility”; thus, the 1758 edition of the Index no longer listed as an entry this general prohibition, but it continued to include several previously prohibited books, including Copernicus’s Revolutions and Galileo’s Dialogue. In 1820, the Inquisition gave the imprimatur to an astronomy textbook by a professor at the University of Rome that presented the earth’s motion as a fact; in so doing, the Inquisition overruled the objections of the chief censor in Rome. In 1822, the Inquisition ruled that in the future this official must not refuse the imprimatur to publications teaching the earth’s motion in accordance with modern astronomy; but a decision about removing from the Index Copernicus’s and Galileo’s books was postponed. In 1833, while deliberating on a new edition of the Index, Pope Gregory XVI decided that it would omit those books, but that this omission would be accomplished without explicit comment; thus, the 1835 edition of the Index for the first time omitted them from the list. This was the final and complete retraction of the book censorship begun in 1616.

However, besides the scientific issue of the earth’s motion, Galileo’s trial also embodied a question of principle, namely whether Scripture is a scientific authority (besides being one for matters of faith and morals). This question is partly methodological or philosophical, and partly theological or hermeneutical. It too culminated in 1633, when the Inquisition’s sentence blamed Galileo in part for denying the scientific authority of Scripture. Thus, one strand of the subsequent affair involves this principle.

One crucial episode in this strand is that eventually the Church ended up agreeing with Galileo. In 1893, in the encyclical Providentissimus Deus, Pope Leo XIII advanced a view of the relationship between biblical interpretation and scientific investigation that corresponds to the one elaborated in Galileo’s Letter to the Grand Duchess Christina. Although Galileo was not even mentioned in the encyclical, the correspondence was easy to detect for anyone acquainted with both documents; so the encyclical has been widely interpreted as an implicit vindication of Galileo’s meta-hermeneutical principle.

A century later, the vindication was made explicit in Pope John Paul II’s rehabilitation of Galileo in 1979–1992. Although this rehabilitation was incomplete, informal, and problematic in several ways, on the hermeneutical issue John Paul was clear and emphatic. In a speech given in 1979, he declared that “Galileo formulated important norms of an epistemological character, which are indispensable to reconcile Holy Scripture and science” (John Paul II 1979, 10). And in a 1992 speech, the pope specified:

The new science, with its methods and the freedom of research that they implied, obliged theologians to examine their own criteria of scriptural interpretation. Most of them did not know how to do so. Paradoxically, Galileo, a sincere believer, showed himself to be more perceptive in this regard than the theologians who opposed him.

(John Paul II 1992, 2)

This brings us to one final strand of the subsequent affair. It involves the condemnation of Galileo-the-person, and consists of various ecclesiastical attempts to revise the trial or rehabilitate him. It is the most elusive, complex, and controversial aspect of the story.

This strand began immediately after Galileo’s death, when questions were raised about whether a convicted heretic like him had the canonical right to have his will executed, and whether he could be buried on consecrated ground. These issues were decided in his favor. But another question was not, namely whether it was proper to build an honorific mausoleum for him in the church of Santa Croce in Florence, which the Tuscan government was considering. This was vetoed by the Church when Galileo died in 1642. However, it finally happened in 1737.

In 1942, the tricentennial of Galileo’s death occasioned a first partial and informal rehabilitation. In the period 1941–1946, this was accomplished by several clergymen who held the top positions at the Pontifical Academy of Sciences, the Catholic University of Milan, the Pontifical Lateran University in Rome, and Vatican Radio. They published accounts of Galileo as a Catholic hero who upheld the harmony between science and religion; who had the courage to advocate the truth in astronomy even against the religious authorities of his time; and who had the religious piety to retract his views outwardly when the 1633 trial proceedings made his obedience necessary.

In 1979, Pope John Paul II began a further informal rehabilitation of Galileo that was not concluded until 1992. In two speeches to the Pontifical Academy of Sciences, and other statements and actions, the pope admitted that Galileo’s trial was not merely an error but also an injustice; that, as already mentioned, Galileo was theologically right about scriptural interpretation, as against his ecclesiastical opponents; that pastorally speaking, his desire to disseminate novelties was as reasonable as his opponents’ inclination to resist them; and that he provides an instructive example of the harmony between science and religion. This rehabilitation was informal because the pope was merely expressing his personal opinions and not speaking ex cathedra. Moreover, it was partial because he deliberately avoided talk or action regarding a formal judicial retraction or revision of the 1633 sentence. Finally, the rehabilitation was opposed by various elements of the Church, including some in the Vatican Commission on Galileo, which he had appointed in 1981, and which attempted to repeat many traditional apologias.

Lessons, Problems, Conjectures

It is beyond the scope of this chapter to elaborate the issues and lessons of the preceding fact-oriented account. However, a few pointers are in order.

First, it is important to distinguish the Copernican Revolution, the original Galileo affair, and the subsequent Galileo affair. This distinction is important because the lessons and issues of one of these episodes do not necessarily coincide with those of the others, and we need to be clear where the relevant evidence comes from. On the other hand, this distinction is not meant to preclude the possibility of formulating lessons that might involve all three episodes, appropriately combined. For example, I have recently defended the following overarching thesis (Finocchiaro 2010): Galileo’s defense of the geokinetic hypothesis is conducted following an approach characterized by rational-mindedness, open-mindedness, and fair-mindedness; further, it is his crucial contribution to the Copernican Revolution, his chief crime at the trial, and a viable model for an effective defense of Galileo himself from the many criticisms of him in the past four centuries.

Second, the most widely drawn lesson from the Copernican Revolution is the realization that mankind is not the physical center of creation, but rather inhabits an ordinary planet circling an ordinary star in an ordinary galaxy. This thesis was formulated with classic incisiveness by Sigmund Freud, who paired it with Charles Darwin’s evolutionary theory demoting the human species from the special place it had been regarded as having in the phenomenon of organic life. Freud also speculated that his own discovery of the unconscious amounted to a comparable revolution in the domain of the mind. This thesis has recently been criticized, being called a myth, in part for being anachronistic (Danielson 2009). However, this criticism is not convincing, since it is based on a one-sided analysis of the historical situation, which contained a mixture of attitudes, one of which did indeed correspond to the Freudian interpretation. Hence, this lesson remains an open question deserving further reflection, especially with regard to the religious implications.

Third, and more to the point, there is the problem of what, if anything, the Galileo affair proves regarding the relationship between science and religion. As traditionally interpreted, Galileo’s trial epitomizes the conflict between science and religion. This is well known, but it is important to stress here that this interpretation has been advanced not only by relatively injudicious writers who have recently been widely discredited (John William Draper and Andrew Dickson White), but also by such scientific, philosophical, and cultural icons as Bertrand Russell, Albert Einstein, and Karl Popper. At the opposite extreme, there is the revisionist thesis that the trial really shows the harmony between science and religion. Here it should be understood that this interpretation does not merely deny the traditional thesis but reverses it. Its most significant advocate is Pope John Paul II, for whom this was the key point he wanted to make in his rehabilitation of Galileo in 1979–1992.

The harmony interpretation begins by distinguishing between the Catholic religion as such and men and institutions of the Church. It then goes on to say that the injustices and errors were committed by men and institutions for which they and not the Church are responsible; so the conflict was between a scientist and some churchmen. In relation to the relationship between science and religion, the correct view is the one elaborated by Galileo himself, which the Church later adopted as its own. That view says that God revealed himself to humanity in two ways, through his work and through his word. His word, namely Holy Scripture, aims to give us information which we cannot discover by examining his work. But to find out what his work is like, we need to observe it by using our bodily senses and by reasoning about it with that other aspect of the divine work which is our mind. In short, Scripture is an authority only on questions of faith and morals, not on scientific factual questions about physical reality. In Galileo’s trial, a key difficulty was the misunderstanding of these principles by the churchmen in power. Once these principles are clarified, as Galileo himself ironically contributed to doing, the conflict between science and religion evaporates and continues to subsist only in the imagination of people who do not know better.

In contrast to both the conflict and harmony theses, I claim that the trial did have both conflictual and harmonious aspects when viewed in terms of science and religion, but that these are elements of its surface structure and that its most profound deep structure lies rather in the clash between cultural conservation and innovation. My argument is as follows.

First, as already mentioned, the 1633 Inquisition sentence condemned Galileo for two beliefs: that the earth moves and that Scripture is not a scientific authority. The second issue involved a disagreement between those (like Galileo) who held and those (like the Inquisitors) who denied that it is proper to defend the truth of a physical theory contrary to the Bible. That is, if in this controversy we take the Copernican theory of the earth’s motion to represent science and Scripture to represent religion, then Galileo was the one claiming that there is no real incompatibility between the two, whereas the Inquisition was the one claiming that the apparent conflict between Copernicanism and Scripture was real. It follows that there is an irreducible conflictual element in Galileo’s trial, between those who believed and those who denied that there is a conflict between Scripture and science. The irony of the situation is that it was the victim who held the more fundamentally correct view. However, insofar as that Galilean non-conflictual view is the more nearly correct one, then the content of that view suggests an important harmonious element in the trial.

Furthermore, both conflict and harmony exist at the level of the surface structure of the situation. If we move to a deeper cultural aspect, then we must say that Galileo was not the only one who held that there was no conflict: many of those who agreed with him on this question of principle were themselves churchmen. For example, the author of the first published (1622) defense of Galileo was the Dominican friar Tommaso Campanella; and the author explicitly condemned in the Index decree of 1616 was the Carmelite friar Paolo Foscarini, whose book argued that the earth’s motion is compatible with Scripture. That is, in Galileo’s time, there was a division within Catholicism between those who did and those who did not accept the scientific authority of Scripture. A similar split existed in scientific circles. A further division existed in both domains with regard to the other main issue of Galileo’s trial, namely the proposition of the earth’s motion. Thus, rather than having an ecclesiastical monolith on one side clashing with a scientific monolith on the other, the real conflict was between two attitudes crisscrossing both. The most fruitful way of conceiving the two factions is to describe them as conservatives or traditionalists on one side and progressives or innovators on the other. The real conflict was between these two groups. In this sense, Galileo’s trial illustrates the clash between cultural conservation and innovation, and is an episode where the conservatives happened to win. This conflict is one that operates in such other domains of human society as politics, art, economy, and technology. It cannot be eliminated without stopping social development; it is a moving force of human history.

Finally, after Galileo’s condemnation, as mentioned earlier, the interpretation and evaluation of the trial became a cause célèbre in its own right. Even those who nowadays advocate the harmonious account of the trial, do not deny that the key feature of the subsequent affair was indeed a conflict between science and religion. For example, Pope John Paul II, believing that the lesson from Galileo’s trial is the harmony between science and religion, wanted to stress this lesson in order to put an end to the subsequent, very real, but presumably unjustified, science-versus-religion conflict. Regarding this subsequent controversy, the science-versus-religion conflict is indeed an essential feature of it, much more an integral part of it than of the original trial. However, underlying such surface structure there may be a cultural deep structure; but in this case the deep structure is probably the phenomenon of the birth and evolution of cultural myths and their interaction with documented facts.

Note

1 Mayaud (2005) documents several of these objections to Copernicanism by Martin Luther, Achilles Pirmin Gasser, Bartolomeo Spina, and Giovanni Maria Tolosani (3:76, 84–87; 6:134–138).

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