Galileo was definitely not a martyr of science. In fact, he was mistaken in important aspects. Today we know that the tides are caused by the gravitational influence of the Moon and the Sun, not the motion of the Earth. We know that the Sun is not the center of the universe, but just another star in the Milky Way that orbits the center of our galaxy, which is also in motion.
We should not hastily conclude that Galileo didn’t make any contribution to science. Although he wasn’t right on in all of his theories, it is evident that he did contribute notably to scientific progress. He is even known as the founder of modern science. His contribution in the field of astronomy consists, above all, in his astronomical observations with different telescopes that he constructed by himself. Galileo saw the roughness of the Moon’s surface, four satellites of Jupiter, sunspots, the phases of Venus, stars that are invisible to the naked eye, and nebulae. Galileo knew that other astronomers would carry these observations further, but he was the first one who raised an eyepiece to the heavens and caused a chain reaction of astronomical discoveries.
What is seldom considered is how Galileo helped the Church, especially in her understanding of the harmony between faith and reason, not merely in theory, which had already been developed during the age of Scholasticism, but in the face of new discoveries in science. Nevertheless, weren’t they ecclesiastics of the Catholic Church who condemned him to house arrest and prohibited him from spreading the Copernican doctrine? To understand his contributions, it is necessary to know the historical and cultural context and the relationship between Galileo and the Church. Here I will not elaborate the entire history; rather, I only intend to mention some necessary considerations.
Copernicus died in 1543, and that same year his book, De Revolutionibus, was published, declaring that the Sun was the center of the universe, and that everything went around the Sun. Andreas Osiander received from the hands of Copernicus (who was already on his deathbed) the text of De Revolutionibus for publication. Osiander, however, decided first to write a preface to the book, perhaps without Copernicus’s authorization. According to this preface, the Copernican hypothesis was not dealing with the reality of the universe. It was only an alternative mathematical method to make predictions. For this reason, Osiander said it was unnecessary to take the Copernican hypothesis seriously. That is why ecclesiastics did not condemn Copernicanism until 1616, when some astronomers did in fact begin to take it seriously. The explosion of a supernova in 1604 called into question the Ptolemaic doctrine of the incorruptibility of the heavens. The doubt increased when the observations Galileo started in 1609 showed that some celestial objects did not orbit the Earth.
The possibility that Copernican doctrines would turn out correct seemed to shake the foundations of Christian theology, which according to many theologians was connected to Aristotelian cosmology. Aristotle, Ptolemy, St. Thomas Aquinas, and many great thinkers and astronomers had considered the Earth as the center of the universe. The theory of the four elements of the sublunar world and of ether for the world beyond the Moon dominated for many centuries. Sacred Scripture, as well, seemingly supported geocentrism. It did not fit in the minds of the ecclesiastics that Scripture or St. Thomas or Aristotle could be wrong in this. Besides, our experience tells us that the Earth doesn’t move. In the age of the Counterreformation, who was Galileo to put into check the doctrine believed for so many centuries? He had not even received the minor orders like Copernicus, neither had he studied theology like the Jesuits who disagreed with him. Galileo was officially the first mathematician of the Great Duke of Tuscany. It was an important and respected position. Nevertheless, this position did not provide him with an authoritative voice in theology.
The ecclesiastics could not deny the facts, though. Some, like the Jesuit Clavius, dedicated the rest of their lives to explain how the recently observed phenomena could be compatible with Aristotelian doctrine. Others, like Christopher Borro, studied the hypothesis of Tycho Brahe, who said that the planets went around the Sun while the Sun orbited the Earth. The ecclesiastics came to the point of seeing without much difficulty that the heavens were corruptible, but the doctrine of geocentrism remained untouchable. They allowed heliocentrism to be spoken about as a means to calculate the positions of the stars and planets, but not as an explanation of reality. Galileo, however, kept insisting. It was then that the need to clarify the matter arose.
1616 was the year of the first judgment about Copernicanism. Three books that supported the Copernican doctrine were condemned. Two of them were only suspended until corrected. The name of Galileo was not even mentioned in the process. Cardinal Bellarmine, one of the most renowned theologians of the Church back then, only warned Galileo not to defend the Copernican theory. Galileo submitted and asked Cardinal Bellarmine for a certificate of this warning, which he did receive.
Galileo was the friend of Cardinal Maffeo Barberini and had helped his nephew, Francisco Barberini, obtain his doctorate in the University of Pisa. When Maffeo Barberini was elected Pope in 1623, he raised his nephew to the College of Cardinals. Two other freinds of Galileo had important positions in the Church, Giovanni Ciampoli and Virginio Cesarini. On the other hand, Galileo made himself the enemy of the Jesuits, first of Orazio Grassi because of their dispute over comets; and, later, of Christopher Scheiner, because of their controversy over sunspots. Scheiner also said that if geocentrism turned out false, then it would be more prudent to adhere to Tycho’s alternative since it didn’t contradict the Scriptures.
Galileo was given an imprimatur in 1632 for his Dialogue, but without revealing that he had been given a warning in 1616. A few months later, the Pope summoned him to Rome.
Galileo was not a heretic, but neither was he a saint. He was not exemplary in his personal life, which we are not going to consider, nor in his way of responding to the prudent judgments of the Church. After demanding that Sacred Scripture be interpreted not literally, but allegorically, he quoted the famous phrase of Baronius: “Spiritui Sancto mentem fuisse nos docere quomodo ad caelum eatur, non quomodo caelum gradiatur,” as if nothing in the Bible had any authority at all over the physical world. Then he tried to show how Sacred Scripture supported the Copernican hypothesis. Moreover, while he demanded that the first criterion of our knowledge be empirical observation and that the interpretation of Sacred Scripture should conform itself with these observations, he showed no real proofs in favor of Copernicanism. These proofs would still not be produced for a long time: in 1837 Bessel demonstrated the Earth’s motion using stellar parallax; and in 1851 Foucault proved the same thing using a pendulum. In that case, Bellarmine was right when he told Galileo to consider the Copernican system a hypothesis until there were irrefutable demonstrative proofs in its favor.
Neither was Galileo prudent in the publication of some of his works. In his Dialogue he presented in the mouth of Simplicius, the ridiculous Aristotelian, the argument that Pope Urban VIII (previously Maffeo Barberini) had told him personally over the impossibility of certitude in scientific theories. Simplicio said that if we tried to explain the Earth’s motion with the tides, we would be limiting divine power and wisdom. God could “confer reciprocal movement to the element of water,” for God is all-powerful, whereas our explanations have their limits. Galileo testified that he didn’t realize it, but that did not appease the Pope. In addition, after his condemnation, Galileo allowed his Dialogue to be translated into Latin and published in Germany. Thus he did not fulfill his oath of 1633.
This does not mean that he did not leave behind a legacy both in science and in the Catholic Church, which he remained always a member of. Galileo was right in some respects regarding the interpretation of the Scriptures. According to some ecclesiastics, the Fathers of the Church had been unanimous in the literal interpretation of the Bible passages that referred to the motion of the Sun and the Earth. In this case they were to be followed blindly, for the Council of Trent had given this norm: “In matters of faith and morals [...] no one relying on his own judgment and distorting the Sacred Scriptures according to his own conceptions, shall dare to interpret them contrary to that sense which Holy Mother Church [...] has held and does hold, or even contrary to the unanimous agreement of the Fathers, even though such interpretations were not at any time to be published.” The Fathers, however, had not been unanimous. Galileo used almost the very exegetical principles that Saint Augustine employed in his commentary to Genesis (De Genesi ad litteram). Nonetheless, this was not even an issue of faith or morals, but only a scientific one.
The Catholic Church has learned from the Galileo case this lesson of criteriology and prudence. Concerning criteriology, John Paul II recognized in his speech on 31 October 1992: “In reality, the Scriptures do not deal with the details of the physical world, whose knowledge is confined to human experience and reasoning.” Concerning prudence, in the same speech the Pope quoted a letter of Saint Robert Bellarmine to Father Foscarini: “In the presence of eventual scientific proofs [...] it would be ‘better to say that we don’t understand it, instead of stating that what is demonstrated is false.’”
This is why, for example, the Magisterium of the Church has not pronounced anything about the existence of extraterrestrials. Science is discovering more and more how hard it is to fit all the conditions for there to be life on any planet, and the Bible tells us that Jesus died once and for all for the salvation of mankind. Nevertheless, the question about the possibility of the existence of life on another planet remains open. Perhaps someday extraterrestrial life forms will be discovered. Applying to this possibility what Bellarmine said in the already quoted letter: “Then it would be necessary to go through with the utmost consideration in explaining the Scriptures that seem contrary.”
“Sacred Scripture can never be mistaken,” wrote Galileo in his letter to Benedetto Castelli. It’s true, since reason and faith never contradict each other. They are two distinct sources for knowledge of the truth, and they also have some points in common. The possibility of this relation between science and faith is precisely another lesson that has been learned, thanks to Galileo.
The Catholic Church has never been an enemy to scientific development. It is enough to take into account that several pioneers of the sciences were Catholic priests: Gregor Mendel, Georges Lemaître, Pierre Gassendi, and Saint Albert the Great, just to name a few, among so many others that could be mentioned.
“Faith and reason are like two wings on which the human spirit rises to the contemplation of truth” (Fides et ratio, introduction). In the light of what we have seen, Galileo should not be considered a sign of contradiction, but rather a sign of unity between science and faith.
Joseph A'Hearn, LC studies for the priesthood in Rome.