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The Galileo affair was an early 17th century political, religious, and scientific controversy regarding the astronomer Galileo Galilei's defence of heliocentrism, the idea that the Earth revolves around the Sun. It pitted supporters and opponents of Galileo within both the Catholic Church and academia against each other through two phases: an interrogation and condemnation of Galileo's ideas by a panel of the Roman Inquisition in 1616, and a second trial in 1632 which led to Galileo's house arrest and a ban on his books.Blackwell (1991, p. 2). Blackwell (1991, p. 50) dates the start of the Galileo affair to 1610. Finocchiaro (1989, p. 1) puts it a few years later, in 1613.
In 1610, Galileo published his Sidereus Nuncius ( Starry Messenger) describing the observations that he had made with his new, much stronger telescope, amongst them the Galilean moons of Jupiter. With these observations and additional observations that followed, such as the phases of Venus, he promoted the heliocentric theory of Nicolaus Copernicus published in De revolutionibus orbium coelestium in 1543. Galileo's opinions were met with opposition within the Catholic Church, and in 1616 the Inquisition declared heliocentrism to be both scientifically indefensible and heretical. Galileo went on to propose a theory of tides in 1616, and of comets in 1619; he argued (incorrectly) that the tides were evidence for the motion of the Earth.
In 1632, Galileo published his Dialogue Concerning the Two Chief World Systems, which defended heliocentrism while describing geocentrists as "simpletons". Responding to mounting controversy, the Roman Inquisition tried Galileo in 1633 and found him "vehemently suspect of heresy", sentencing him to house arrest. At this point, heliocentric books were banned and Galileo was ordered to abstain from holding, teaching or defending heliocentric ideas after the trial.
The affair was complex, with Pope Urban VIII originally being a patron and supporter of Galileo before turning against him. Urban initially gave Galileo permission to publish on the Copernican theory so long as he treated it as a hypothesis, but after the publication of the Dialogue in 1632, the patronage was broken off. Historians of science have since corrected numerous false interpretations of the affair. (2025). 9781624661327, Hackett Publishing Company, Incorporated. ISBN 9781624661327McMullin (2008)
Galileo's contributions caused difficulties for Theology and natural philosophers of the time, as they contradicted scientific and philosophical ideas based on those of Aristotle and Ptolemy and closely associated with the Catholic Church. In particular, Galileo's observations of the phases of Venus, which showed it to circle the Sun, and the observation of moons orbiting Jupiter, contradicted the geocentric model of Ptolemy, which was backed and accepted by the Roman Catholic Church, Extract of page 1 Extract of page 4 and supported the Copernican model advanced by Galileo.
Jesuit astronomers, experts both in Church teachings, science, and in natural philosophy, were at first skeptical and hostile to the new ideas; however, within a year or two the availability of good telescopes enabled them to repeat the observations. In 1611, Galileo visited the Collegium Romanum in Rome, where the Jesuit astronomers by that time had repeated his observations. Christoph Grienberger, one of the Jesuit scholars on the faculty, sympathized with Galileo's theories, but was asked to defend the Aristotelian viewpoint by Claudio Acquaviva, the Father General of the Jesuits. Not all of Galileo's claims were completely accepted: Christopher Clavius, the most distinguished astronomer of his age, never was reconciled to the idea of mountains on the Moon, and outside the collegium many still disputed the reality of the observations. In a letter to Johannes Kepler of August 1610,Drake (1978, p. 162), Sharratt (1994, p. 86), Favaro (1900, 10:421–423) . Galileo complained that some of the philosophers who opposed his discoveries had refused even to look through a telescope:Galileo did not name the philosophers concerned, but Galileo scholars have identified two of them as Cesare Cremonini and Giulio Libri (Drake, 1978, pp. 162, 165; Sharratt, 1994, p. 87). Claims of similar refusals by bishops and cardinals have sometimes been made, but there appears to be no evidence to support them.
In 1611, the same year that Galileo visited the Collegium Romanum, his theories first came to the attention of the Roman Inquisition. A commission of cardinals working with the inquisition made inquiries into Galileo's activities, and asked the city of Padua if he had any connections to Cesare Cremonini, a professor at the university of Padua who had been charged with heresy by the Inquisition. These inquiries marked the first time Galileo's name was brought before the inquisition.Bucciantini, Massimo; Camerota, Michele; Giudice, Franco (2015). Galileo’s Telescope ''Il. Cambridge, Massachusetts: Harvard University Press. p. 4. .
Geocentrists who did verify and accept Galileo's findings had an alternative to Ptolemy's model in an Tychonic system proposed some decades earlier by Tycho Brahe – a model in which, for example, Venus circled the Sun. Tycho argued that the distance to the stars in the Copernican system would have to be 700 times greater than the distance from the Sun to Saturn. (The nearest star other than the Sun, Proxima Centauri, is over 28,000 times the distance from the Sun to Saturn.) Moreover, the only way the stars could be so distant and still appear the sizes they do in the sky would be if even average stars were gigantic – at least as big as the orbit of the Earth, and of course vastly larger than the Sun. (See the articles on the Tychonic System and Stellar parallax.)
Galileo became involved in a dispute over priority in the discovery of sunspots with Christoph Scheiner, a Jesuit. This became a bitter lifelong feud. Neither of them, however, was the first to recognise sunspots – the Chinese had already been familiar with them for centuries.Sharratt (1994, p. 98).
At this time, Galileo also engaged in a dispute over the reasons that objects float or sink in water, siding with Archimedes against Aristotle. The debate was unfriendly, and Galileo's blunt and sometimes sarcastic style, though not extraordinary in academic debates of the time, made him enemies. During this controversy one of Galileo's friends, the painter Cigoli, informed him that a group of malicious opponents, which Cigoli subsequently referred to derisively as "the Pigeon league","La legha del Pippione" (Favaro, 1901, 11:476) . "The Pigeon" ("il Pippione") was Cigoli's derisive nickname for the presumed leader of the group, Lodovico delle Colombe (Sharratt, 1994, p. 95; Favaro, 1901, 11:176, 11:228–229, 11:502). It is a pun on Colombe's surname, which is the feminine plural form of the Italian word for "Dove." "Pippione" is a now obsolete Italian word with a triple entendrebesides meaning "young pigeon", it was also a jocular colloquialism for a testicle, and a Tuscan dialect word for a fool. was plotting to cause him trouble over the motion of the Earth, or anything else that would serve the purpose.Drake (1978, p. 180), Favaro (1901) 11:241–242) . According to Cigoli, one of the plotters asked a priest to denounce Galileo's views from the pulpit, but the latter refused. Nevertheless, three years later another priest, Tommaso Caccini, did in fact do precisely that, as described below.
Geostaticism agreed with a literal interpretation of Scripture in several places, such as , , , , (but see varied interpretations of ). Heliocentrism, the theory that the Earth was a planet, which along with all the others revolved around the Sun, contradicted both geocentrism and the prevailing theological support of the theory.
One of the first suggestions of heresy that Galileo had to deal with came in 1613 from a professor of philosophy, poet and specialist in Greek literature, Cosimo Boscaglia. Four Treatises for the Reconsideration of the History of Science, Fabio J. a. FarinaHeilbron (2010), p. 369 In conversation with Galileo's patron Cosimo II de' Medici and Cosimo's mother Christina of Lorraine, Boscaglia said that the telescopic discoveries were valid, but that the motion of the Earth was obviously contrary to Scripture:
Dr. Boscaglia had talked to Madame Christina for a while, and though he conceded all the things you have discovered in the sky, he said that the motion of the Earth was incredible and could not be, particularly since Holy Scripture obviously was contrary to such motion. – Letter from Benedetto Castelli to Galileo, 1613–14
Galileo was defended on the spot by his former student Benedetto Castelli, now a professor of mathematics and Benedictine abbot. The exchange having been reported to Galileo by Castelli, Galileo decided to write a letter to Castelli, expounding his views on what he considered the most appropriate way of treating scriptural passages which made assertions about natural phenomena.Sharratt (1994, p. 109). Later, in 1615, he expanded this into his much longer Letter to the Grand Duchess Christina.Sharratt (1994, pp. 112–126).
Lorini and his colleagues decided to bring Galileo's letter to the attention of the Inquisition. In February 1615, Lorini accordingly sent a copy to the Secretary of the Inquisition, Cardinal Paolo Emilio Sfondrati, with a covering letter critical of Galileo's supporters:Drake (1978, p. 240), Sharratt (1994, pp. 110–111), Favaro (1907, 19:297–298) .
On March 19, Caccini arrived at the Inquisition's offices in Rome to denounce Galileo for his Heliocentrism and various other alleged heresies supposedly being spread by his pupils.Sharratt (1994, p. 111), Favaro (1907, 19:307–311) .
Galileo soon heard reports that Lorini had obtained a copy of his letter to Castelli and was claiming that it contained many heresies. He also heard that Caccini had gone to Rome and suspected him of trying to stir up trouble with Lorini's copy of the letter.Drake (1978, p. 241), Favaro (1895, 5:291–292) . As 1615 wore on he became more concerned, and eventually determined to go to Rome as soon as his health permitted, which it did at the end of the year. By presenting his case there, he hoped to clear his name of any suspicion of heresy, and to persuade the Church authorities not to suppress heliocentric ideas.
In going to Rome Galileo was acting against the advice of friends and allies, and of the Tuscan ambassador to Rome, Piero Guicciardini.Langford, 1992, p. 79
Foscarini sent a copy of his book to Bellarmine, who replied in a letter of April 12, 1615.Blackwell (1991, pp. 265–67), Finocchiaro (1989, pp. 67–9). A copy of Finocchiaro's translation of the letter is available on-line. Galileo is mentioned by name in the letter, and a copy was soon sent to him. After some preliminary salutations and acknowledgements, Bellarmine begins by telling Foscarini that it is prudent for him and Galileo to limit themselves to treating heliocentrism as a merely hypothetical phenomenon and not a physically real one. Further on he says that interpreting heliocentrism as physically real would be "a very dangerous thing, likely not only to irritate all scholastic philosophers and theologians, but also to harm the Holy Faith by rendering Holy Scripture as false." Moreover, while the topic was not inherently a matter of faith, the statements about it in Scripture were so by virtue of who said them – namely, the Holy Spirit. He conceded that if there were conclusive proof, "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, demonstrating that heliocentrism merely "saved the appearances" could not be regarded as sufficient to establish that it was physically real. Although he believed that the former may well have been possible, he had "very great doubts" that the latter would be, and in case of doubt it was not permissible to depart from the traditional interpretation of Scriptures. His final argument was a rebuttal of an analogy that Foscarini had made between a moving Earth and a ship on which the passengers perceive themselves as apparently stationary and the receding shore as apparently moving. Bellarmine replied that in the case of the ship the passengers know that their perceptions are erroneous and can mentally correct them, whereas the scientist on the Earth clearly experiences that it is stationary and therefore the perception that the Sun, Moon and stars are moving is not in error and does not need to be corrected.
Bellarmine found no problem with heliocentrism so long as it was treated as a purely hypothetical calculating device and not as a physically real phenomenon, but he did not regard it as permissible to advocate the latter unless it could be conclusively proved through current scientific standards. This put Galileo in a difficult position, because he believed that the available evidence strongly favoured heliocentrism, and he wished to be able to publish his arguments.Sharratt (1994, pp. 115-25).
At a meeting of the cardinals of the Inquisition on the following day, Pope Paul V instructed Bellarmine to deliver this result to Galileo, and to order him to abandon the Copernican opinions; should Galileo resist the decree, stronger action would be taken. On February 26, Galileo was called to Bellarmine's residence and ordered,
With no attractive alternatives, Galileo accepted the orders delivered, even sterner than those recommended by the Pope.Drake (1978, p. 253). Galileo met again with Bellarmine, apparently on friendly terms; and on March 11 he met with the Pope, who assured him that he was safe from prosecution so long as he, the Pope, should live. Nonetheless, Galileo's friends Sagredo and Castelli reported that there were rumors that Galileo had been forced to recant and do penance. To protect his good name, Galileo requested a letter from Bellarmine stating the truth of the matter. This letter assumed great importance in 1633, as did the question whether Galileo had been ordered not to "hold or defend" Copernican ideas (which would have allowed their hypothetical treatment) or not to teach them in any way. If the Inquisition had issued the order not to teach heliocentrism at all, it would have been ignoring Bellarmine's position.
In the end, Galileo did not persuade the Church to stay out of the controversy, but instead saw heliocentrism formally declared false. It was consequently termed heretical by the Qualifiers, since it contradicted the literal meaning of the Scriptures, though this position was not binding on the Church.
Francesco Ingoli, a consultor to the Holy Office, recommended that De revolutionibus be amended rather than banned due to its utility for calendrics. In 1618, the Congregation of the Index accepted his recommendation, and published their decision two years later, allowing a corrected version of Copernicus' book to be used. The uncorrected De revolutionibus remained on the Index of banned books until 1758.Finnochiario (2007), p. 154
Galileo's works advocating Copernicanism were therefore banned, and his sentence prohibited him from "teaching, defending… or discussing" Copernicanism. In Germany, Kepler's works were also banned by the papal order.
Galileo's Dialogue Concerning the Two Chief World Systems, which was published in 1632 to great popularity, was an account of conversations between a Copernican scientist, Salviati, an impartial and witty scholar named Sagredo, and a ponderous Aristotelian named Simplicio, who employed stock arguments in support of geocentricity, and was depicted in the book as being an intellectually inept fool. Simplicio's arguments are systematically refuted and ridiculed by the other two characters with what Youngson calls "unassailable proof" for the Copernican theory (at least versus the theory of Ptolemy – as Finocchiaro points out, "the Copernican and Tychonic systems were observationally equivalent and the available evidence could be explained equally well by either"Finocchiaro (1997), p. 54)), which reduces Simplicio to baffled rage, and makes the author's position unambiguous. Indeed, although Galileo states in the preface of his book that the character is named after a famous Aristotelian philosopher (Simplicius in Latin, Simplicio in Italian), the name "Simplicio" in Italian also had the connotation of "simpleton."Finocchiaro (1997), p. 82); Moss & Wallace (2003), p. 11) Authors Langford and Stillman Drake asserted that Simplicio was modeled on philosophers Lodovico delle Colombe and Cesare Cremonini. Pope Urban demanded that his own arguments be included in the book, which resulted in Galileo putting them in the mouth of Simplicio. Some months after the book's publication, Pope Urban VIII banned its sale and had its text submitted for examination by a special commission.
Galileo was interrogated while threatened with physical torture. A panel of theologians, consisting of Melchior Inchofer, Agostino Oreggi and Zaccaria Pasqualigo, reported on the Dialogue. Their opinions were strongly argued in favour of the view that the Dialogue taught the Copernican theory.Sharratt (1994, pp. 172–3]).
Galileo was found guilty, and the sentence of the Inquisition, issued on 22 June 1633, was in three essential parts:
According to popular legend, after his abjuration Galileo allegedly muttered the rebellious phrase "and yet it moves" ( Eppur si muove), but there is no evidence that he actually said this or anything similar. The first account of the legend dates to a century after his death.Drake (1978, p. 356) The phrase "Eppur si muove" does appear, however, in a painting of the 1640s by the Spanish painter Bartolomé Esteban Murillo or an artist of his school. The painting depicts an imprisoned Galileo apparently pointing to a copy of the phrase written on the wall of his dungeon.Drake (1978, p. 357)
After a period with the friendly Archbishop Piccolomini in Siena, Galileo was allowed to return to his villa at Arcetri near Florence, where he spent the rest of his life under house arrest.On two occasions only during this period he was given permission to travel away from Arcetri. In October 1636 he was permitted to travel to Poggibonsi to meet the French ambassador to Rome, François de Noailles (Sharratt,1994, p. 184; Favaro 1905, 16:507 . In March 1638 he was permitted to travel to Florence for medical treatment, where he spent several months before returning to Arcetri (Sharratt,1994, p. 186; Favaro 1905, 17:290, 310–11) . He continued his work on mechanics, and in 1638 he published a scientific book in Holland. His standing would remain questioned at every turn. In March 1641, Vincentio Reinieri, a follower and pupil of Galileo, wrote him at Arcetri that an Inquisitor had recently compelled the author of a book printed at Florence to change the words "most distinguished Galileo" to "Galileo, man of noted name".Drake (1978, p. 414)
However, partially in tribute to Galileo, at Arcetri the first academy devoted to the new experimental science, the Accademia del Cimento, was formed, which is where Francesco Redi performed controlled experiments, and many other important advancements were made which would eventually help usher in The Age of Enlightenment.
Dava Sobel argues that during this time, Urban had fallen under the influence of court intrigue and problems of state. His friendship with Galileo began to take second place to his feelings of persecution and fear for his own life. The problem of Galileo was presented to the pope by court insiders and enemies of Galileo, following claims by a Spanish cardinal that Urban was a poor defender of the church. This situation did not bode well for Galileo's defense of his book.Sobel, Dava (2000, pp. 223–225) 1999. Galileo's Daughter. London: Fourth Estate. .
In his 1998 book, Scientific Blunders, Robert Youngson indicates that Galileo struggled for two years against the ecclesiastical censor to publish a book promoting heliocentrism. He claims the book passed only as a result of possible idleness or carelessness on the part of the censor, who was eventually dismissed. On the other hand, Jerome K. Langford and Raymond J. Seeger contend that Pope Urban and the Inquisition gave formal permission to publish the book, Dialogue Concerning the Two Chief World Systems, Ptolemaic & Copernican. They claim Urban personally asked Galileo to give arguments for and against heliocentrism in the book, to include Urban's own arguments, and for Galileo not to advocate heliocentrism.
Some historians emphasize Galileo's confrontation not only with the church, but also with Aristotelian philosophy, either secular or religious.
Redondi's hypothesis concerning the hidden motives behind the 1633 trial has been criticized, and mainly rejected, by other Galileo scholars.Ferrone and Firpo (1986) and Westfall (1989, pp. 58–93) provide comprehensive overviews of some of the criticisms that have been levelled at Redondi's theory. Briefer criticisms can be found in Pagano (1984, pp. 43–48), Gosselin (1985), Westfall (1987), Baumgartner (1989), Drake (1990, p. 179 – footnote), Blackwell (1991, pp. 154–155, footnote 47), Wallace (1991, pp. vii, 67, 81–84), Sharratt (1994, p. 149), Artigas et al. (2005, pp. 214, 222, 225–227), and Beretta (2005b, pp. 192, 202–203). However, it has been supported recently, as of 2007, by novelist and science writer Michael White.White (2007)
In 1979, Pope John Paul II expressed the hope that "theologians, scholars and historians, animated by a spirit of sincere collaboration, will study the Galileo case more deeply and in loyal recognition of wrongs, from whatever side they come." However, the Pontifical Interdisciplinary Study Commission constituted in 1981 to study the case did not reach any definitive result. Because of this, the Pope's 1992 speech that closed the project was vague, and did not fulfill his intentions expressed in 1979.
On February 15, 1990, in a speech delivered at La Sapienza University in Rome,An earlier version had been delivered on December 16, 1989, in Rieti, and a later version in Madrid on February 24, 1990 (Ratzinger, 1994, p. 81). According to Feyerabend himself, Ratzinger had also mentioned him "in support of" his own views in a speech in Parma around the same time (Feyerabend, 1995, p. 178). Cardinal Ratzinger (later Pope Benedict XVI) cited some current views on the Galileo affair as forming what he called "a symptomatic case that illustrates the extent to which modernity’s doubts about itself have grown today in science and technology".Ratzinger (1994, p. 98). As evidence, he presented the views of a few prominent philosophers including Ernst Bloch and Carl Friedrich von Weizsäcker, as well as Paul Feyerabend, whom he quoted as saying:
Ratzinger did not directly say whether he agreed or disagreed with Feyerabend's assertions, but did say in this same context that "It would be foolish to construct an impulsive apologetic on the basis of such views."
In 1992, it was reported that the Catholic Church had turned towards vindicating Galileo: Daniel N. Robinson citing John Paul II in Human nature in its wholeness: a Roman Catholic perspective edited by D. N. Robinson, G. M. Sweeney and R. Gill, Front Cover
In January 2008, students and professors protested the planned visit of Pope Benedict XVI to La Sapienza University, stating in a letter that the pope's expressed views on Galileo "offend and humiliate us as scientists who are loyal to reason and as teachers who have dedicated our lives to the advance and dissemination of knowledge". In response the pope canceled his visit. The full text of the speech that would have been given was made available a few days following Pope Benedict's cancelled appearance at the university. La Sapienza's rector, Renato Guarini, and former Italian Prime Minister Romano Prodi opposed the protest and supported the pope's right to speak. Also notable were public counter-statements by La Sapienza professors Giorgio Israel; This last citation is a reprint of the original article that appeared in L'Osservatore Romano on January 15, 2008. Scroll down for access. and Bruno Dalla Piccola.
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