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The case of Galileo Galilei (1564–1642) is probably of no interest anymore except to the seasoned historian. There is no reason to bring up the subject again if not for the fact that now and then the enemies of the Catholic Church still cite the Church's condemnation of Galileo as evidence for the Church’s alleged “anti-science” attitude or as a case against the Church’s doctrine of papal infallibility. 

According to a popular but grossly exaggerated report, the Inquisition, by order of the pope, tortured Galileo for teaching that it was not the sun that moved, but the earth that moved around the sun. It has been claimed that the Church’s hostility to science retarded the progress of science through the Renaissance and that the wrongful condemnation of Galileo was proof that the pope was not infallible.

To see the flaws behind these claims, observe first that the idea, which says that the sun was the center of the universe and that the earth was merely one of the planets that moved around it, was not Galileo’s original invention. The hypothesis was known to Nicholas Copernicus (1473–1543) long before Galileo was born. This theory, known today as the heliocentric theory, was not readily accepted during Copernicus’ time because it contradicted the geocentric theory of Aristotle, which was the accepted theory at that time. The geocentric theory states that the Earth is at the center of the universe and that all heavenly bodies, including the sun, move around it. Many scientists accepted the idea as a plausible theory. By using it, mariners could navigate the seas, and astronomers could predict eclipses. The common folk welcomed the theory because it was everyone’s observation. Catholic and non-Catholic theologians were also comfortable with it because it gave due importance to the Earth, where the Son of God became man.

Nicholas Copernicus

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The Geocentric and Heliocentric Model

Original image by Niko Lang; SVG version by Booyabazooka

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However, the Catholic Church was never hostile to the heliocentric theory. Copernicus was himself a Catholic priest, or at least an ordained deacon. He dedicated his book, De revolutionibus orbium coelestium (On the Revolution of the Heavenly Spheres), to Pope Paul III, who received it respectfully. If some Catholic theologians spoke against the Copernican theory, it was simply because the heliocentric model was not the accepted scientific view at that time. And, for the same reason, the heliocentric theory was rejected, not exclusively by Catholic theologians, but by scientists themselves and by Protestant theologians. For example, Martin Luther also condemned it in his "Table Talk," saying:

"Men pay heed to an astrologer who contends that it is the earth that moves, and not the heavens or the firmament, the sun and the moon. If a man yearns for a reputation as a profound scientist, he should invent some new system. This madman would subvert the whole science of astronomy; but Scripture tells us that Joshua bade the sun, and not the earth, to stand still." Quoted by Reuben Parsons in Some Lies and Errors of History, p. 82. The reference to Joshua is from Jos 10:12–13.

Why, then, did Galileo get into trouble with the Inquisition but not Copernicus? Because Copernicus was more tactful and less audacious than Galileo. He presented his theory not as a replacement for the well-accepted geocentric model but only as a method for charting the motion of the planets, as Ptolemy’s system was. Also, he did not get his theory published until 15 years later, when he was already on his deathbed in 1543. Galileo, on the other hand, wanted to overturn the geocentric model of the universe. He campaigned against popular belief to convince the world that the geocentric model was wrong and that the heliocentric model was right.

Galileo’s fascination with the heliocentric theory started when, using his improved telescope, he discovered the motion of the moons of Jupiter, which revolved around it and not around the earth as the geocentric theory expected. He also discovered that Mercury and Venus had phases like the moon, a fact that was difficult to reconcile with the geocentric theory but that was quite consistent with the heliocentric model of Copernicus. With full exuberance, Galileo published his discoveries. When he went to Rome in 1611, Cardinal Robert Bellarmine prudently warned him of the disturbance that his writings might cause, especially because Galileo tended to exaggerate his case and ridicule his adversaries.

Galileo Showing the Doge of Venice How to Use the Telescope

A painting by Giuseppe Bertini (1825-1898)

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However, the Vatican did not condemn heliocentrism or the Copernican theory. It even allowed Galileo to teach heliocentrism as a hypothesis, not a fact. However, Galileo continued to proclaim his observations as indisputable evidence of his theory and stubbornly refused to recognize the hypothetical character of his views. In a letter to Paolo Foscarini (a supporter of Galileo) on April 12, 1615, Cardinal Bellarmine made the point that if only he and Galileo were to teach heliocentrism as a hypothesis rather than a fact, then there should be no problem. And if heliocentrism could later be demonstrated as fact, then he would rather say that the Holy Scripture was misunderstood than insist that the heliocentric model was false. See Cardinal Robert Bellarmine's 1615 Letter to Foscarini.

Galileo had not yet fully demonstrated the Copernican theory when he was already teaching it as fact. The three arguments that he brought forward, based on the phenomena of the tides, the movement of the solar spots, and the apparent movement of the planets, were, as Laplace noted, merely proofs by analogy and did not amount to an incorrigible demonstration. He also assumed the orbits of the planets to be perfectly circular, which was contradicted by Kepler’s observations. But Galileo found it difficult to see that his empirical verification of the heliocentric model did not yet guarantee its absolute truth. Incidentally, this is the same mistake that many scientists today commit when they teach Darwinian evolution as if it were an indubitable fact rather than simply a scientific hypothesis.

On February 19, 1616, the Inquisition submitted Galileo’s teachings to the Congregation of the Holy Office for advice. The theologians in the Holy Office mistakenly found the heliocentric theory “foolish and absurd in philosophy, and formally heretical.” After being notified of their opinion, Pope Paul V, therefore, requested that Cardinal Bellarmine notify Galileo that if he continued to teach his theory as fact, then the Holy Office would start proceedings against him. Cardinal Bellarmine clarified on May 26, 1616, that Galileo was not required to change his opinion regarding the theory, but he needed to be silent about it rather than defend or teach it. See Galileo Trial 1616 Documents.

Galileo Galilei

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Galileo Before the Holy Office (Cardinal Bellarmine in Red)

A painting by Joseph-Nicolas Robert-Fleury (1797-1890)

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Galileo was quiet for a while. But in 1632, Galileo published his Dialogue Concerning the Two Chief World Systems, which featured a discussion between the advocates of the geocentric theory and the defenders of the Copernican theory, with the Copernicans winning all the issues and the advocates of the geocentric theory looking like fools. The derisive dialogue, which even used the silly Simplicio as spokesman for the Pope, brought Galileo again before the Inquisition.

Galileo was right in his insistence that in astronomy, direct observation of nature must take the place of reliance on the authority of Aristotle. He was also right, not merely in defending the Copernican theory but in his claim against the theologians that the theory did not contradict Holy Scripture. But his audacity antagonized the churchmen. On June 22, 1633, the Holy Office decreed that Galileo, by his disobedience and by his teachings, had rendered himself “vehemently suspected of heresy.” The Vatican subsequently detained Galileo and sentenced him to remain silent about the heliocentric theory for the rest of his life. See Documents in the Galileo Case 1633.

The Holy Office was wrong and unfair in accusing Galileo of heresy. But, in fairness to the Holy Office, the authorities did not torture Galileo  as the enemies of the Catholic Church claimed. Neither the trial documents nor the letters he wrote to his friends mentioned any torture. Instead of being imprisoned in a detestable dungeon, he was put on “house arrest” and permitted to reside in the lovely Villa Medici of his friend, the Tuscan Ambassador Niccolini, and later, in the residence of another friend, the Archbishop Ascanio Piccolomini in Siena. Galileo’s supposed “arrest” was so comfortable that he was able to continue his research on mechanics. In December 1633, he returned to his villa at Arcetri, near Florence, where he completed his Dialogues Concerning the Two New Sciences.

Regarding the issue of papal infallibility, there can be no doubt that it was never truly an issue. It was the Congregation of the Holy Office, appointed by the pope, that condemned Galileo. But the popes—Pope Paul V in 1616 and Pope Urban VIII in 1633—did not ratify the decisions of 1616 and 1633. Since papal infallibility cannot be delegated to a congregation, the absence of the pope's signature in the documents puts the question of papal infallibility out of the question.

The other claim that the Catholic Church has been hostile to science is nothing less than preposterous. Have we forgotten the many contributions made to science by thousands of Catholics, many of whom were learned churchmen? Have we forgotten the name of Roger Bacon (1220-1292), the Franciscan friar who antedated Francis Bacon in precisely formulating the principles of the scientific method? Have we forgotten Theodoric of Frieberg (1250-1310), the Dominican friar who made the first geometrical analysis of the rainbow; Guy De Chauliac (1300-1368), the Papal physician who was the father of modern surgery; Johannes Gutenberg (1398-1468), who invented the printing press; (Andreas Vesalius (1574-1564), the founder of modern anatomy; Antoine Lavoisier (1743-1794), the father of modern chemistry; Alessandro Volta (1745-1827), the inventor of the electric battery; Augustin-Jean Fresnel (1788-1827), a pioneer of the science of optics that led to the wide acceptance of the wave theory of light;  André-Marie Ampère (1775-1836), the father of electrodynamics; Gregor Johann Mendel (1822-1884), Augustinian priest and founder of modern genetics; Henri Becquerel (1852-1908), who discovered radioactivity; Guglielmo Marconi (1874-1937), the father of wireless communications, Georges Lemaître (1894-1966), a Belgian Catholic priest and father of the Big Bang theory, and the numerous other scientists who were also children of the Church? For a longer list, see List of Catholic Clergy Scientists and List of Lay Catholic Scientists.

The unfortunate confrontation of Galileo with the Inquisition taught the Church some very valuable lessons. Among other things, it highlighted the importance of keeping the sphere of theology and religion distinct from the realm of empirical science and the danger of tying the doctrines of our faith with a particular philosophy, scientific theory, or worldview.

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