Tit_Lo que deberíamos saber sobre Galileo

What we should know about Galileo 

Author: Mariano Artigas
Published in: Scripta Theologica, 32, pp. 877-896.
Publication date: 2000 (updated and illustrated: January 2006)


1. How did Galileo die?

2. Why was Galileo condemned?

     2.1. The 1616 trial

     2.2. The 1633 trial

3. Questions and interpretations


The Galileo case is often used to claim that the Catholic Church is the enemy of scientific progress. I am therefore struck by the fact that quite a few Catholics, including

Lo que deberíamos saber sobre Galileo

priests, religious and others who have theological knowledge, know this case in a rather superficial and sometimes even wrong way.

A few years ago I was in Rome giving a lecture at doctoral course. In one session I spoke about the Galileo case. At the end, a priest who was working on his doctoral thesis came to talk to me. He was very angry and said to me: how is it possible that I, a Catholic priest, who has spent years in a seminar and now work on my thesis doctoral dissertation in Rome, can find out today that Galileo was not killed by the Inquisition? You were absolutely right to be puzzled. Since I have similar experiences with some frequency, I have decided to write this article, in which I intend to summarize, very briefly, the central aspects of the Galileo case: what we know for sure did or did not happen; what issues continue to be discussed; what is, at final, the current state of the question in its main dimensions.

What causes the ignorance and confusion surrounding the Galileo case is a subject that deserves to be studied: topic . In part it may be due to the overly partisan use that has often been made of this case: some, wishing to attack the Church, have over-emphasised what was in their interests or distorted the facts, and others, in defending the Church, have sometimes used an overly facile apologetic approach, ignoring the complexities of the case. There are now many rigorous studies on Galileo, so that it is possible to establish objectively what we know and what we do not know. The Catholic Church has shown, through its highest representative, the Pope, a clear desire to clarify the topic, and has not been reluctant to acknowledge unreservedly the mistakes that its representatives may have made with Galileo, even asking for forgiveness. It seems to be a good time to propose a dispassionate summary of the famous case.

 How did Galileo die?

The first point that should be clear is that Galileo was not killed by the Inquisition, or by anyone else. He died a natural death. Galileo was born on Tuesday 15 February 1564 in Pisa, and died on Wednesday 8 January 1642, at his home, a villa in Arcetri, just outside Florence. He was therefore almost 78 years old when he died (it is possible to find a difference of one year even in official documents, because at that time in Florence the years began to be counted on 25 March, the date of the Incarnation of the Lord). Vincenzo Viviani, a young disciple of Galileo's who stayed with him continuously for the last thirty months, says that his health was very poor: he had had severe arthritis since he was 30 years old, and to this was added "a constant and almost unbearable irritation of the eyelids" and "other ailments that come with such an advanced age, especially when one has been consumed by much study and vigil". He adds that, in spite of everything, he was still full of projects of work, until finally "he was seized by a fever that slowly consumed him and a strong palpitation, so that for two months he became more and more exhausted, and finally, on a Wednesday, which was the 8th of January 1642, at about four in the morning, he died with philosophical and Christian firmness, at the age of seventy-seven years, ten months and twenty days". So there was no bonfire, or anything like it.

Nor was he sentenced to death. The only trial in which he was convicted took place in 1633, and there he was sentenced to imprisonment which, in view of his good dispositions, was immediately commuted to house arrest, so that he was never imprisoned. According to common rules, he should have been in the Inquisition prison during the trial, but in fact he was never there: before the beginning of the trial he stayed at the Tuscan embassy in Rome, located in Palazzo Firenze, where the ambassador lived; during the trial he was required at some points to stay in the Inquisition building, but then he was allowed to stay in rooms that were reserved for the ecclesiastics who worked there, allowing food to be brought to him from the Tuscan embassy; and at the end of the trial he was allowed to stay at Villa Medici, one of the finest villas in Rome, with splendid gardens, which was owned by the Grand Duke of Tuscany. All this is explained by the fact that Galileo was officially the first mathematician and philosopher of the Grand Duke of Tuscany, an important territory (including Florence, Pisa, Livorno, Siena, etc.) and traditionally well connected with the Holy See, and the Tuscan authorities exercised their good offices to ensure that Galileo was treated as well as possible in Rome, as indeed he was. The Tuscan ambassador, Francesco Niccolini, was very fond of Galileo, and did everything possible to ensure that he suffered as little as possible from the trial, and that he did not go to prison. Niccolini succeeded in having his prison sentence commuted to confinement at the Villa Medici at the end of the trial. After a few days he was allowed to move to Siena, where he stayed in the palace of the archbishop, Monsignor Ascanio Piccolomini, who was a great admirer and friend of Galileo and treated him splendidly during the several months he stayed in his house, so that he recovered from the trauma the trial undoubtedly caused him (in 1633, when the trial took place, Galileo was 69 years old). He was then allowed to move to his house on the outskirts of Florence, where he remained until he died a natural death in old age. He finished his most important work, and published it, in 1638, after the trial.

At final, Galileo was not sentenced to death, but to imprisonment, which was not carried out because it was commuted: first, by a stay of several days at Villa Medici in Rome; then, by a stay of several months in the palace of his friend the Archbishop of Siena; and then (at the end of 1633), he was allowed to reside, in a sort of house arrest, in his own house, the Villa del Gioiello, in Arcetri, outside Florence, where he lived and worked until his death.

Nor was Galileo ever subjected to torture or physical ill-treatment. Certainly, making him go to Rome from Florence to stand trial, at the age of 69, is bad treatment, and the same can be said of the psychological stress he endured during the trial and the final condemnation, followed by forced abjuration. This is true. From the psychological point of view, with the repercussions that this can have on health, Galileo had to suffer for these reasons and, in fact, when he arrived in Siena after the trial, he was in poor condition. But it is equally true that he was not subjected to any of the physical mistreatment typical of the time. Some authors have claimed that during the trial, at the end, he was subjected to torture on one occasion; however, authors of all persuasions agree agreement, with virtual unanimity, that this did not actually happen. In the concluding phase of the trial, on one occasion, there is a threat of torture by the court, but all the available evidence is in favour of this being a pure formality which, due to the regulations of the Inquisition, the court had to mention, but without intending to carry out torture and without it actually being carried out (it is also recorded that in Rome torture was not carried out on people of Galileo's age). After his condemnation, in Siena, Galileo recovered. He then suffered from various illnesses, but these were the same illnesses he had been suffering from for many years, which became worse with age. He even became completely blind, but this had nothing to do with the trial.

 Why was Galileo condemned? 

What is most striking is not the physical ill-treatment, which, as we have just seen, did not exist, but the very fact that Galileo was condemned, with all the stress and suffering that this implies. He was certainly not a murderer, nor a thief, nor an evildoer in any of the usual senses of the word. So why was he condemned, and what was the condemnation?

There are usually two trials against Galileo: the first in 1616, and the second in 1633. Sometimes only the second is mentioned. The reason is simple: the first trial actually existed, because Galileo was denounced to the Roman Inquisition and the trial went ahead, but Galileo was never summoned before the court: the denounced learned that the denunciation and the trial existed through the comments of other people, but the court never said anything to him, nor summoned him, nor condemned him. For this reason, it is often not considered to have been a real trial, although in fact the case was opened and some procedural steps were taken over a period of months. The trial of 1633, on the other hand, was a full-blown trial: Galileo was summoned to appear before the tribunal of the Inquisition in Rome, had to appear and testify before that court, and was finally condemned. These are two very different trials, separated by many years; but they are related, because what happened in 1616 largely conditioned what happened in 1633.

 The 1616 trial 

In 1616 Galileo was accused of supporting the heliocentric system proposed in antiquity by the Pythagoreans and in modern times by Copernicus: he claimed that the Earth is not stationary at the centre of the world, as was generally believed, but revolves around itself and the Sun, as do other planets in the Solar System. This seemed to go against texts in the Bible which say that the Earth is stationary and the Sun moves, from agreement with experience; moreover, the Tradition of the Church had so interpreted the Bible for centuries, and the Council of Trent had insisted that Catholics should not admit interpretations of the Bible which deviated from the unanimous interpretations of the Holy Fathers.

The events of 1616 ended with two extra-judicial acts. On the one hand, a decree of the Congregation of the Index, dated 5 March 1616, was published, by which three books were included in the Index of banned books: On the Revolutions of the Polish canon Nicolaus Copernicus, published in 1543, in which the heliocentric theory was exposed in a scientific way; a commentary by the Spanish Augustinian Diego de Zuniga, published in Toledo in 1584 and in Rome in 1591, in which some passages of the Bible of agreement were interpreted with Copernicanism; and a booklet by the Italian Carmelite Paolo Foscarini, published in 1615, where it was defended that the Copernican system is not against the Sacred Scripture. Any other book teaching the same doctrines was affected by the same censures. The reason given in the decree for these censures was that the doctrine that the earth moves and the sun is at rest is false and completely contrary to Sacred Scripture. Moreover, Galileo was personally admonished to abandon the heliocentric theory and to refrain from defending it.

Foscarini's booklet was banned outright. On the other hand, the books by Copernicus and Zuniga were only suspended until some passages were corrected. In the case of Zuniga, what was to be changed was very brief. In the case of Copernicus, it concerned several passages where it had to be explained that heliocentrism was not a true theory, but only a useful artifice for astronomical calculations. In fact, these corrections were prepared and approved after four years, in 1620.

We may wonder why so much importance was attached to something that, today, seems simple: when the Bible speaks of scientific matters, it often adopts the way of speaking proper to the culture, to the time or simply to ordinary experience. Indeed, this was one of the arguments used by Galileo in his Letter to Benedetto Castelli, which was circulated in handwritten copies (Castelli was a Benedictine, a friend and disciple of Galileo, professor of mathematics at the University of Pisa), and at greater length in his Letter to the Grand Duchess of Tuscany, Christina of Lorraine (mother of the then Grand Duke of Tuscany, Cosimo II), to whom echoes of the biblical accusations against Galileo had reached.

To understand the background to the issue, three problems need to be mentioned. First, Galileo had become famous with his astronomical discoveries in 1609-1610. Using the telescope that he himself was instrumental in perfecting, he discovered that the moon has irregularities like the earth, that four satellites revolve around Jupiter, that Venus has phases like the moon, that there are spots on the surface of the sun that change places, and that there are many more stars than can be seen with the naked eye. Galileo used these discoveries to criticise Aristotelian physics and support Copernican heliocentrism. The Aristotelian professors, who were many and powerful, felt that Galileo's arguments contradicted their science, and were sometimes ridiculed. These professors seriously attacked Galileo and, when they ran out of answers, some resorted to theological arguments (the alleged contradiction between Copernicus and the Bible).

Secondly, the Catholic Church was at that time particularly sensitive to those who interpreted the Bible on their own, departing from Tradition, because the confrontation with Protestantism was very strong. Galileo defended himself against those who said that heliocentrism was contrary to the Bible by explaining why it was not, but in doing so he was playing the theologian, which was considered dangerous at the time, especially when, as in this case, one departed from traditional interpretations. Galileo argued quite well as a theologian, stressing that the Bible does not claim to teach us science and accommodates itself to the knowledge of the time, and even showed that there were precedents in the Tradition of the Church that allowed the use of arguments such as the ones he proposed. But in an age of fierce theological polemics between Catholics and Protestants, it was frowned upon for a layman to lecture theologians and to propose somewhat strange novelties.

Thirdly, the traditional worldview, which placed the Earth at the centre of the world, seemed to be of agreement with ordinary experience: we see the Sun, the Moon, the planets and the stars moving, but if the Earth were moving, things should happen that do not: projectiles thrown upwards would fall backwards, we do not know how the clouds would be attached to the Earth without also falling backwards, such rapid movement should be noticed. Moreover, this traditional worldview seemed much more consistent with the Christian perspective of a world created in view of man, and also with the Incarnation and Redemption of mankind through Jesus Christ; Indeed, among those who had accepted Copernican ideas was Giordano Bruno, who argued that there are many inhabited worlds and ended up holding more or less heretical doctrines (Bruno was burned as a result of his condemnation by the Roman Inquisition in 1600, although it should be noted, not as an apology but for the sake of clarity, that he was not properly a scientist, even if he used Copernicanism as a starting point).

The events of 1616 culminated in a decree of the Congregation of the Index, dated 5 March 1616, banning the books mentioned, with the nuances already noted. The decree was issued in the name of the Congregation, and is signed by the cardinal prefect and the secretary of the Congregation, not by the pope. Of course, such an act subject was done with the mandate or approval of the Pope and, in some way, it compromised the Pope's authority, but in no way can it be considered as an act in which the infallibility of the Pope is at stake: on the one hand, because it is not signed by the Pope and does not even mention him; on the other hand, because it is an act of government of a Congregation, not an act of magisterium; and furthermore, because it does not pretend to define a doctrine in a definitive way. This was well known then, as it is now; as test we can mention a letter from Benedetto Castelli to Galileo, written on 2 October 1632, when Galileo had already been ordered to appear before the Inquisition in Rome. Castelli has spoken to the Father Commissary of the Holy official document, Vincenzo Maculano, and has defended the orthodoxy of the position of Copernicus and Galileo, adding that he has several times discussed the matter with pious and very intelligent theologians, and they have seen no difficulty; he adds that Maculano himself has told him that he is of agreement and that, in his opinion, the question should not be settled by resorting to the Sacred Scripture. It is easy to see that these opinions, dealt with in the same Commissary of the Holy official document, would not make sense if the decree of the Index of 1616 could be interpreted as having the scope of an infallible or definitive magisterium.

In the deliberations of the Holy See, prior to the decree, eleven consultors of the Holy See official document were asked for their opinion, and they ruled, on February 24, 1616, that to say that the Sun is immobile at the centre of the world is absurd in philosophy and moreover formally heretical, because it contradicts many places in Scripture as expounded by the Holy Fathers and theologians, and to say that the Earth moves is also absurd in philosophy and at least erroneous in faith. This opinion of the consulting theologians is often taken as if it were the opinion of the authority of the Church, but it is not: it was only the opinion of those persons. The only public act of Church authority was the decree of the Congregation of the Index, and that decree does not say that the heliocentric doctrine is heretical: it says that it is false and opposed to the Sacred Scripture. The nuance is important, and every theological scholar knew it then and knows it now. No one considered then, nor should they now, that heliocentrism was condemned as heresy, because it is not true. This explains why Galileo and other equally Catholic people continued to accept heliocentrism; Galileo knew (and it was true) that he had shown, in his letters to Castelli and Christina of Lorraine, that heliocentrism could be reconciled with Sacred Scripture, using principles that were not new, but had support in the Tradition of the Church.

The decision of the Church authority in 1616 was wrong, although it did not label heliocentrism as heresy. Galileo and his ecclesiastical friends set out to have the decree overturned. They could have succeeded: it was a disciplinary decree which, although accompanied by a doctrinal assessment, did not condemn heliocentrism as heresy, nor was it an act of infallible magisterium.

Another important aspect to bear in mind is that, although Galileo's criticisms of the traditional position were well founded, neither he nor anyone else at the time had arguments to prove that the Earth moves around the Sun. This assertion seemed rather absurd, as the theologians of the Holy See described it official document. In a famous letter, Cardinal Robert Bellarmine, one of the most influential theologians at the time, asked both Foscarini and Galileo to use heliocentrism only as an astronomical hypothesis, without claiming it to be true or engaging in theological arguments, in which case there would be no problem. But Galileo, to defend himself against personal accusations and to try to keep the Church from intervening in the matter, launched into a strong defence of Copernicanism, moving to Rome and trying to influence ecclesiastical personalities; this perhaps had the opposite effect, causing the Church authority to intervene to curb Galileo's propaganda, which, at least in its criticisms, was quite convincing.

In addition to the decree of the Congregation of the Index, the ecclesiastical authorities took another decision that affected Galileo personally and that had a decisive influence on his trial, 17 years later. Specifically, by order of the Pope (Paul V), Cardinal Bellarmine summoned Galileo (who was then in Rome, engaged in the propaganda of Copernicanism) and, at the Cardinal's residency program on 26 February 1616, admonished him to abandon the Copernican theory. The Pope had ordered Bellarmine to issue this admonition, adding that, if Galileo did not want to abandon the theory, the Commissioner of the Holy official document, in front of a notary and witnesses, should order him not to teach, defend or treat this doctrine, and that if he refused to do so, he should be imprisoned. It is recorded that Bellarmine gave the warning. But among the documents that have been preserved there is one that has given rise to discussions on the force and scope of this precept: it says that, following Bellarmine's admonition, the Father Commissary of the Holy official document (the Dominican Michelangelo Segizzi) transmitted the above-mentioned precept to him; but this document is unsigned. All sorts of interpretations have been made subject; the most extreme is that it is a document deliberately falsified in 1616 or 1633 to kill Galileo; but this seems very unlikely. With the documents we possess, it is very difficult to know exactly how the meeting between Bellarmine and Galileo developed. But it is clear that Galileo understood perfectly well that from now on he could not argue in favour of Copernicanism, and indeed he did so for years. Indeed, the trial to which he was subjected 17 years later, in 1633, was motivated by Galileo's apparent disobedience to this precept.

 The 1633 trial 

If the decree of the Congregation of the Index in 1616 was wrong, it was also wrong to forbid Galileo to discuss or defend Copernicanism. Galileo knew it. Yet he obeyed. He always was and always wanted to be a good Catholic. But he knew that the 1616 ban was based on a misunderstanding and he wanted to correct the misunderstanding. He even warned of the danger of scandal that the ban could cause in the future, if it were to be proved with certainty that the earth revolved around the sun. His friends were at agreement with him.

In 1623 circumstances coincided which seemed to favour a revision of the decisions of 1616, or at least to make it possible for the case for Copernicanism to be made, however carefully. The main factor was the election as Pope of Cardinal Maffeo Barberini, who took the name Urban VIII. He had for years been an admirer of Galileo, to whom he had even dedicated a Latin poem praising his astronomical discoveries. Moreover, from the very beginning he had several of Galileo's friends and supporters in positions of great trust. In 1624 Galileo went to Rome and the Pope received him six times with great cordiality. But Galileo found that, when he was trying out the matter of Copernicanism, although Urban VIII did not consider it heretical (we have already seen that it was never declared as such), he considered it to be a doctrinally reckless position and, moreover, was convinced that it could never be proved: he said that the same observable effects explained by this theory could be due to other causes, otherwise we would be limiting the omnipotence of God. It was an argument that apparently had a lot of force, and it seemed that whoever claimed to have proved Copernicanism was limiting God's omnipotence.

Nevertheless, the mood of the new Pope and the strategic position of his friends led Galileo to embark on an old pending project : to write a great work discussing Copernicanism and, of course, arguing in its favour. He would simply present it as a dialogue between a supporter of geocentrism and a supporter of heliocentrism, without settling the question. And I would add the Pope's argument. But the intelligent reader would already realise who was right.

Moreover, Galileo thought he had a new argument to prove the motion of the Earth: the argument from the tides. According to Galileo, the tides could only be explained by assuming the motion of the Earth (and he did not accept, as if it sounded like astrology, that they were due to the influence of the Moon). He even wanted to title his work that way, as a treatise on the tides, but the Pope knew that he intended to use that title and, as it sounded too realistic (as indeed it was), he advised another title that did not sound like a test of the Earth's motion (of course, as we know, the tides argument was wrong). Galileo changed the title of the book to Dialogue Concerning the Two Great Systems of the World, the Ptolemaic and the Copernican. A very apt title, partly due to the interference of a Pope who did not want the motion of the Earth to be treated as real: but that was undoubtedly Galileo's main intention in his work. Galileo was prepared to concede whatever was necessary, provided he could publish a work containing the arguments against the traditional position and in favour of Copernicanism.

Galileo finished writing the Dialogue in 1630, and took it to Rome to obtain ecclesiastical permission to print it. The permission had to be granted by the Master of the Sacred Palace, the Dominican Niccolò Riccardi, who did not know astronomy but was an admirer of Galileo and had always been eager to help him. Now Riccardi found himself in a bind. He implied that there would be no problems, although a number of details would have to be worked out. Galileo returned to Florence, the plague placed serious limitations on traffic and mail between Florence and Rome, and there began a chain of misunderstandings that prolonged the granting of permission and made Galileo nervous. Within a year, Galileo sought and obtained the intervention of the Grand Duke of Tuscany and his ambassador in Rome to obtain permission. Riccardi, who was also a Tuscan and a relative of the ambassador's wife, came under severe pressure. He finally granted permission for the book to be printed in Florence, but with a number of conditions which he made known to Galileo and the Inquisitor of Florence. Riccardi knew what the Pope thought: that Copernicanism could only be treated as a mathematical hypothesis, not as a representation of reality; the conditions and warnings he gave were aimed at ensuring this, which was not at all clear in Galileo's work.

Galileo introduced changes, but certainly not as many as Riccardi would have introduced and the Pope would have wished. In the book, Simplicius, the character who defends the traditional position of Aristotle and Ptolemy, always loses out. Simplicius was one of the most famous ancient commentators on Aristotle, but in Galileo's work he gave the impression that his arguments and his attitude corresponded too well to his name. Moreover, the Pope's favourite argument appeared at the end of the work: after all the physical and philosophical arguments had been set out, Simplicius, precisely Simplicius, used that argument, and although Salviati, the defender of Copernicus (and Galileo) approves of it, the ending is very brief and forced. To add to the confusion, an Introduction approved by Riccardi, explaining that this work was not intended to establish Copernicanism as a true theory, appeared printed on a different subject from the rest of the work, giving the impression of a false addition.

The Dialogue was completed in Florence on 21 February 1632. Galileo immediately sent copies everywhere, including to his friends in other European countries. There were still communication problems with Rome because of the plague, so the first copies did not reach Rome until mid-May. One of them was given to Cardinal Francesco Barberini, the Pope's nephew and right-hand man, whom Galileo had helped years before to obtain his doctorate, and whom he considered, like his uncle the Pope, as a great personal friend.

In 1632 the Pope's main concern was not the movement of the Sun and the Earth. He was at plenary session of the Executive Council development the Thirty Years' War, which began in 1618 and did not end until 1648, and which pitted the whole of Europe in two halves, Catholics and Protestants. At that time there were very complex problems, because Catholic France was rather on the side of the Protestants in Sweden and Germany, at odds with the other Catholic powers, Spain and the Empire. Urban VIII had been cardinal legate in Paris and tended to side with the French, fearing, moreover, excessive Spanish arrogance, and trying not to lose France. These were very difficult balances. The problems were serious. On 8 March 1632, at a meeting of cardinals with the Pope, Cardinal Gaspar Borgia, protector of Spain and ambassador of the Catholic King, openly accused the Pope of not defending the Catholic cause properly. An extraordinarily violent situation was created. Under these conditions, Urban VIII was especially obliged to avoid anything that could be interpreted as not defending the Catholic faith in a sufficiently clear manner.

It was precisely in these circumstances, in mid-May, that the first copies of the Dialogue began to arrive in Rome. At first nothing happened. But two months later, in mid-July, it became known that the Pope was very angry with the book, that he was trying to stop its dissemination, and that he was going to set up a commission to study it and pass judgement on it.

The documentation we possess does not allow us to know what provoked the Pope's anger and his decision. Galileo always attributed it to the actions of his enemies (who were not few and far between), who would have informed the Pope in a tendentious way, biased against him. For example, in addition to denouncing the book as defending Copernicanism, contrary to the decree of 1616, they would have pointed out that one of the three characters in the dialogue, Simplicius, who is always the loser, is the one who makes the Pope's favourite argument about the omnipotence of God and the limits of our explanations. This might have seemed a deliberate mockery, and it seems to have been interpreted as such: several years later, Galileo was still sending a message to the Pope, from his villa in Arcetri, letting him know that no such thing had ever crossed his mind. Moreover, as has been noted, Urban VIII's personal circumstances at the time were difficult, and he could not tolerate the publication of a book, appearing with ecclesiastical permission from Rome and Florence, which defended a theory condemned by the Congregation of the Index in 1616 as false and contrary to the Sacred Scripture.

The Pope set up a commission to examine the accusations against Galileo, and it was ruled that the matter should be sent to the Holy official document (or Roman Inquisition), from which Galileo, who lived in Florence, was ordered to appear in Rome before that tribunal during the month of October 1632. After delaying attempts lasting several months, on 30 December 1632, the Pope with the Inquisition let it be known that, if Galileo did not appear in Rome, someone would be sent to ascertain his health and, if it appeared that he was able to go to Rome, he would be taken in chains. The Pope strongly advised the Grand Duke to refrain from intervening, because the matter was serious. The Tuscan authorities decided to advise Galileo to go to Rome. Ambassador Niccolini, who knew the Pope well and spoke with him frequently, warned that arguing with the Pope and contradicting him was the best way to ruin Galileo. When the pope spoke to Niccolini about the trouble caused by Galileo, he became furious on several occasions. They all warned Galileo that he had better go to Rome and be ready to obey whatever he was told, because if he took any other attitude the consequences would be detrimental to him.

Galileo arrived in Rome on Sunday 13 February 1633, in a litter provided by the Grand Duke, after waiting at the border of the Papal States because of the plague that was still raging in Florence. The Tuscan ambassador, Francesco Niccolini, behaved marvellously towards Galileo, continually intervening on his behalf with the authorities in Rome, agreement according to the Grand Duke's instructions. They managed to keep Galileo out of the prison of the Holy official document, as required by the rules. From his arrival in Rome until 12 April (two months), Galileo lived in the Palace of Florence, where the Tuscan embassy and the ambassador's house were located. The authorities advised him to avoid social life, so he did not leave the house, but was treated exquisitely by the ambassador and his wife. Niccolini asked the Pope to keep the matter as brief as possible, but it dragged on because the Inquisition was still deliberating on how to proceed. As the 1616 document forbidding Galileo to deal in any way with Copernicanism had been discovered in the archives of the Holy official document , the trial focused entirely on a single accusation: that of disobedience to the 1616 precept.

Galileo was called to depose the Holy official document on Tuesday 12 April 1633. His defence may seem very strange to us: he denied that, in the Dialogue, he defended Copernicanism. Galileo did not know that the Holy official document had order the opinion of three theologians and that, on 17 April, all three reports concluded without doubt (as indeed they did) that Galileo, in his book, defended Copernicanism; in this case, the theologians were right. This complicated the situation, for a defendant who did not acknowledge a proven error was to be treated very severely by the court. On the other hand, Galileo defended himself by showing a letter which, at his request, Cardinal Bellarmine had written to him after the events of 1616, so that he could defend himself against those who were slandering him; in this letter, Bellarmine attested that Galileo had not had to abjure anything and that he had simply been notified of the prohibition of the Congregation of the Index. But this could also be interpreted against Galileo if it was shown, as was the case, that in his book he argued in favour of the doctrine condemned in 1616. The court focused on nuances of the prohibition made to Galileo in 1616, which Galileo claimed not to remember, because he had kept Bellarmine's document and those nuances were not included there. Unfortunately, Bellarmine had died and could not clarify the situation.

In those days Galileo was still at the Holy official document, although he was not in prison then either. Out of deference to the Grand Duke of Tuscany and at the ambassador's insistence, Galileo was installed in the rooms of the prosecutor of the Inquisition, his meals were brought to him from the Tuscan embassy, and he was allowed to walk around. He stayed there from Tuesday 12 April to Saturday 30 April: 17 full days with their queues.

To unblock the situation, the Father Commissar proposed to the Cardinals of the Holy official document something unusual: to visit Galileo in his rooms and try to convince him to acknowledge his error. He succeeded after a long talk with Galileo on 27 April. The next day, without telling anyone else, he wrote what he had done and the result to the Cardinal nephew of the Pope, who was at Castelgandolfo with the Pope at the time; from this letter it is clear that this action was approved by the Pope: in this way, the tribunal could save its honour by condemning Galileo, and then clemency could be used on Galileo by leaving him confined in his house, as (says the Father Commissary) suggested by Your Excellency (Cardinal Francesco Barberini).

Indeed, on Saturday 30 April Galileo admitted in court that, on re-reading his book, which he had finished some time ago, he realised that, not out of bad faith but out of conceit and a desire to show himself more ingenious than other mortals, he had put forward the arguments in favour of Copernicanism with a force that he himself did not believe they had. From then on, things developed as the Commissioner had foreseen. On the same day Galileo was allowed to return to the palace in Florence, to the ambassador's house. On Tuesday 10 May he was summoned to the Holy official document to present his defence; he produced the original of Cardinal Bellarmine's letter, and reiterated that he had acted with right intention. He was still locked up in the Palazzo Firenze; the ambassador managed to get permission to go for walks to Villa Medici, and even to Castelgandolfo, because it was bad for him not to do any subject exercise. In the meantime, the plague was still raging in Florence, and in a letter he was told that, in the midst of his misfortune, it was fortunate that he was not then in Florence.

On Thursday 16 June, the Congregation of the Holy See official document had, as it does every week, its meeting with the Pope. On this occasion it was held in the Quirinal Palace. Six of the ten Cardinals of the Inquisition were present, as well as the Commissary and the advisor (in the interrogations and, in general, in all the sessions mentioned so far, the Cardinals were not present: there were the officers of the Holy official document who transmitted the conference proceedings to the Congregation of the Cardinals, and these, with the Pope, took the decisions). On that day the Pope decided that Galileo should be examined as to his intentions under threat of torture (in this case it was a purely formal threat, which it was already known beforehand would not be carried out). Afterwards, Galileo was to abjure the suspicion of heresy before the Congregation at plenary session of the Executive Council. He was to be sentenced to imprisonment at the discretion of the Congregation, forbidden in future to deal in any way with topic on the motion of the Earth, the Dialogue was to be banned, and a copy of the sentence was to be sent to the nuncios and inquisitors, especially the one in Florence, to be read out publicly at a meeting at which he was to ensure that the professors of mathematics and philosophy were present. The Pope communicated this decision to Ambassador Niccolini on 19 June. Niccolini asked for clemency, and the Pope, stating something which, as has been pointed out, had already been decided beforehand, replied that, after the sentence, he would see the ambassador again to see how it could be arranged that Galileo should not be in prison. From agreement with the Pope, Niccolini informed Galileo that the case would be over at once and the book would be banned, without saying anything to him about what concerned his person, so as not to cause him further distress.

From Tuesday 21 June to Friday 24 June, Galileo was again at the Holy official document. On Wednesday 22nd Galileo was taken to the convent of Santa Maria sopra Minerva; the sentence was read to him (signed by 7 of the 10 Cardinals of the Holy See official document) and he abjured his opinion about the movement of the Earth in front of the Congregation. This was, for Galileo, the most unpleasant part of the whole process, because it directly affected his person and took place in public in a humiliating way. On Thursday 23rd the Pope, with the Congregation of the Holy official document gathered in the Quirinal, granted Galileo a commutation of his imprisonment to Villa Medici, where he went on Friday 24th. On Thursday 30th Galileo was allowed to leave Rome and move to Siena, Tuscany, to the Archbishop's palace. Galileo left Rome on Wednesday 6 July and arrived in Siena on Saturday 9 July. The Roman nightmare was over.

The sentence of the Inquisition begins with the names of the 10 cardinals of the Inquisition, and ends with the signatures of 7 of them. The Pope, together with the Congregation, decided that Galileo should be condemned and that he should abjure his opinion, but at no point in the text of the sentence is the Pope mentioned; therefore, this document cannot be considered as an act of pontifical magisterium, and even less as an infallible or definitive act of magisterium. The text of the abjuration reads "I curse and detest the aforementioned errors and heresies", but this is not a doctrine defined as heresy by the magisterium of the Church: the text of the abjuration states, as it does, that this doctrine was declared contrary to the Sacred Scripture, and, as we know, this declaration was made by a decree of the Congregation of the Index, which did not constitute an infallible or definitive act of magisterium.

The Archbishop of Siena, Ascanio Piccolomini, was a former disciple, admirer and great friend of Galileo. He had offered several times to put him up in his house, considering, moreover, that it was relatively close to Florence and that Florence was still suffering from the plague. In Siena, Galileo was treated splendidly and recovered from the stress of the previous months. On 1 December 1633, at the request of the Grand Duke of Tuscany, the Pope, together with the Holy See official document, granted Galileo permission to return to his home outside Florence, the Villa del Gioiello, provided that he remained under house arrest, without moving around or socialising. It is recorded that on 17 December Galileo was already at home, and remained there until his death in 1642.

Galileo continued to work in Arcetri. There he completed his Discourses and Demonstrations Concerning Two New Sciences, which was published in 1638 in Holland. It is his most important work, in which he sets out the foundations of the new science of mechanics, which was to develop in that century until it reached 50 years later, with Newton's Mathematical Principles of Natural Philosophy, published in 1687, the formulation that marks the definitive birth of modern experimental science.

 Questions and interpretations 

So far I have tried to present the basic facts of the Galileo trial. I will now turn to the assessment of these facts. Given the perspective I have adopted, I will only briefly touch on a few aspects that I consider particularly interesting.

First of all, can we say that we know the basics about the Galileo trial, and is it possible that there are important unknowns? The answer is that the surviving documents allow us to reconstruct almost all aspects of the trial with great reliability. We have Galileo's interrogations and statements in their entirety, as well as the decisions of the Pope and the Congregation of the Holy See official document. In this area, it is not plausible that new documents will appear that substantially affect what we already know. There are certainly gaps; one of them, quite important, concerns the events of the summer of 1632, from the time the Dialogue arrives in Rome until the Pope convenes the congregation of theologians to decide what is to be done. Who informed the Pope and how? Galileo always regarded his trial as the result of biased information from his enemies. It is possible that documents exist about these events, whose knowledge would allow us to better understand why they unfolded the way they did. We could perhaps know to what extent things could have happened differently. That would not, however, change the facts already known, which include the fact that Galileo pursued his Copernican programme for years, even if outwardly he seemed to have given up on it, and that Urban VIII was very upset when he realised that his admired friend was in fact playing a different game from the one he thought he was playing.

This does not mean that Galileo deliberately lied. But there is no doubt that he considered Copernicanism as a true theory, also after the trial. In his Letter to Christina of Lorraine he had explained at length how the apparent contradiction between Copernicanism and the Bible could be resolved; he was right and he knew it: for this reason he could in good conscience admit Copernicanism, even after the condemnations of 1616 and 1633. The same was true of his friends and other sufficiently well-informed people. This begs the question why the ecclesiastical authorities condemned a theory which, although not completely proven at the time, could be proven and, in fact, received further confirmation in the following years.

To answer this question, we must note that modern experimental science, as we know it today, was still in its infancy and was still in its embryonic stage. Galileo was one of its founding fathers. But the Galileo that the authorities saw was very different from the one we see now, in the light of the development of physics for almost four centuries. Galileo had made some important astronomical discoveries and had been recognised. But he could not prove the motion of the Earth. Modern science was practically non-existent: Galileo's most important contributions to that science were those published, in the Discourses, after the trial. The ecclesiastics (Bellarmine, Urban VIII and many others), as well as most university professors, thought that the motion of the Earth was absurd, because it contradicted many true experiences and, if it existed, it should have consequences which in fact were not observed. It was not easy to take Copernicanism seriously. The theologians who assessed in 1616 the stillness of the sun and the motion of the earth said, first of all, that both were absurd in philosophy. Moreover, they seemed contrary to the Bible. Bellarmine, and other ecclesiastics, warned that if the motion of the earth were ever proved, a number of passages in the Bible would have to be interpreted non-literally; they knew that this could be done, but they thought that the motion of the earth would never be proved and that it was absurd. This does not justify all their actions, but it allows them to be placed in their real historical context and to make them understandable.

Galileo's trial should not be understood as a confrontation between science and religion. Galileo always considered himself a Catholic and tried to show that Copernicanism was not opposed to Catholic doctrine. For their part, the ecclesiastics were not opposed to the progress of science; during his trip to Rome in 1611, Galileo was paid a great public tribute in a ceremony held at the Jesuit Roman high school for his astronomical discoveries. The problem was that they did not consider the motion of the Earth to be a scientific truth, and some (including Pope Urban VIII) were even convinced that it could never be proved.

Galileo's enemies probably played an important role in triggering the process. Galileo's very lively temperament did not help to appease the numerous disputes that his work from 1610 onwards gave rise to. Moreover, he unnecessarily made enemies for himself, so that when the Dialogue was published in 1632, it is easy to imagine that his enemies in Rome could present things to the Pope in such a way that, in view of the difficult circumstances under which Urban VIII was living, he felt offended by Galileo and felt it necessary to intervene forcefully. Urban VIII's temperament also played a role: he had a strong character and thought that Galileo had betrayed his sincere friendship; he repeated several times to Ambassador Niccolini that Galileo had mocked him. It is recorded that, when discussing this topic with Niccolini, Urban VIII was furious. Galileo certainly did not intend in any way to mock the Pope, but it is probable that Galileo's enemies, in the summer of 1632, convinced the Pope otherwise, and that this had a serious influence on the course of events development .

One should not think only of Galileo's personal enemies. The motion of the Earth could easily be seen as a cause of major difficulties for Christianity. If the Earth became just another planet, and if there were many more stars than can be seen with the naked eye, could this not be interpreted along the lines of Giordano Bruno, who claimed that there are many worlds like ours, with their stars and inhabited planets? In that case, what would be the significance of the Incarnation and Redemption of Jesus Christ, what about the salvation of possible intelligent beings who might live elsewhere in the universe? These are questions that are being asked even more forcefully today than they were then, given the remote but real possibility that we might learn that life exists elsewhere in the universe. In fact, it is not difficult to see that Christian revelation refers directly to what is happening with us, and therefore there is no difficulty in principle in integrating other intelligent beings into it. Moreover, the Church teaches that the fruits of the Redemption also apply to people who have lived before the Incarnation, or who live after it, and through no fault of their own do not know the truth of Christianity. But it is understandable that these problems could have had an influence at that time. The association of Copernicanism with Bruno could not have favoured Galileo. It may be recalled that two persons core topic in the condemnation of Copernicanism in 1616 were Pope Paul V and Cardinal Bellarmine; both were Cardinals of the Inquisition when, in 1600, Bruno's trial came to an end, and it may be supposed that, in thinking of Copernicanism, they would see it, as it were, associated with Bruno's theological errors.

The motion of the Earth seemed to affect Christianity from another point of view. Galileo's Dialogue contained very strong criticisms of Aristotle's philosophy, which had been used, at least since the 13th century, as financial aid for theology. In that philosophy it was admitted, for example, that there is finality in the world, and that sensible qualities exist objectively and form the basis of the human knowledge . These ideas seemed to be ruined by Galileo's new mathematical and mechanistic philosophy. The new science was born in polemic with the old natural philosophy, and did not seem to be able to fill the gap left by it. Even if Galileo's criticisms of Aristotelianism were confined to specific aspects of physics, which were certainly to be abandoned, it seemed that the new science was trying to throw out, as they say, the baby with the bathwater. This problem is still relevant today. It can even be said that the scientific progress of the last centuries has made it more and more acute. Many voices are calling for a serious effort to integrate scientific progress into a broader vision that includes the metaphysical and ethical dimensions of human life. In this sense, those who saw in the new science a source of difficulties were not completely wrong. Of course, the problem is not one of science itself, the legitimacy of which it would be absurd to doubt. Scientific progress is ambivalent and the fact that it can be misused does not mean that science should be punished. I am simply trying to underline that, at the heart of the Galileo case, there are some problems that are real, are still current, and still await a solution. What is the scope of the scientific knowledge is one of those problems.

It is recorded that there was an attempt to denounce Galileo to the Holy See for his atomistic philosophy, briefly set out in his 1623 work Il Saggiatore, arguing that Galileo denied the objectivity of sensible qualities (colours, smells, tastes) and that this contradicts the Council of Trent's doctrine on the Eucharist, according to which, after consecration, the sacramental species (accidents of the bread, such as sensible qualities) are found without their natural subject. It has even been said that this was the deeper reason for the accusation against Galileo in 1632, and that the Pope succeeded in making the trial focus on the motion of the earth, because otherwise the consequences would have been much worse. The accusation mentioned did exist, but it seems too much of an exaggeration to focus Galileo's problems there. This question shows, however, that the new physics was accompanied by a mechanistic philosophy which, in part, clashed with generally accepted philosophy and theology, and it is true that this problem remained alive for a long time and is even still alive, in part, today.

The Galileo case did not seriously affect the progress of science. The seed that Galileo planted bore fruit immediately, also in Italy. Within a few decades, Newton brought modern physics to its final birth, and Galileo's work was well established.

Finally, it is interesting to note that there has been no other case similar to the Galileo case. The Galileo case is not one case among others of the same subject. The most similar case is that of evolutionism, but the theory of evolution, within its scientific scope, has never been condemned by any body of the universal Church. If one tries to put issues such as abortion, euthanasia, bioethics, etc. on the same level as the Galileo case, it should be noted that, although these problems include components related to science, they are not strictly scientific problems, but, at most, problems of the application of scientific knowledge. But this would require a specific reflection that goes beyond the objectives I have proposed here.


The data in this article are mostly taken from the National Edition of Galileo's works, prepared by Antonio Favaro: Le Opere di Galileo Galilei, 20 volumes, reprint, G. Barbèra Editore, Firenze 1968. The documents of the trial are found in volume XIX, pp. 272-421, and have also been edited by Sergio Pagano: I documenti del processo di Galileo Galilei, Pontificia Academia Scientiarum, Vatican City 1984.