The Galileo Affair

Why did Galileo get in trouble with the Church?

Many theories have been put forth over the years to explain why Galileo came into conflict with the Church. The mystery arises precisely because Galileo actually stood squarely in the long history of the Church’s support of science. Many churchmen of high standing, such as Cardinal Nicholas of Cusa, had suggested even more radical cosmologies than Galileo did; Copernicus’ work itself had been available without controversy for more than sixty years before Galileo first published his telescopic observations. Most theories explain Galileo's problems with the Church as a clash of strong personalities; as coming from a fear that his ideas would threaten the basis of contemporary theology; or as a reaction by the Pope to the political pressures of the day.

The interpretation of the bible was certainly one of the principal contributing factors to the controversy. At the council of Trent, at the height of the protestant reformation just about twenty years before the birth of Galileo, the Catholic Church had solemnly declared that only the church could authentically interpret the bible and that private interpretation was forbidden. Now in 1616, just as the controversy about a sun-centered Copernican universe was heating up, the church’s holy office declared that Copernicanism was formally heretical because it contradicted many passages in the bible (e.g. Joshua 10: 11-13, in which the sun stops moving in the sky). Galileo had already written several essays on the interpretation of the bible in which he essentially said that the bible was written to teach us how to go to heaven and not how the heavens go. In these documents he essentially anticipated by about 400 years what the Catholic Church would teach about the interpretation of the bible, but he did so privately.

In these documents and in many others Galileo certainly showed himself to be a person with an acerbic writing style who courted controversy. He also had friends in high places, including Prince Cesi, the head of the scientific “Academy of the Lynxes”. Unfortunately for Galileo, Prince Cesi died just before the controversy arose over Galileo’s book: “Dialogue Concerning Two Chief World Systems” (Dialogue).

For many years Galileo had a close friendship with cardinal Maffeo Barberini who had even sent Galileo a latin ode composed by the cardinal in praise of Galileo’s telescopic discoveries. This same cardinal became Pope Urban VIII, the reigning pontiff at the time of the church’s condemnation of Galileo.

In the dialogue, Galileo provided persuasive, but not conclusive, evidence for a Sun-centered system. In so doing, he challenged the classical Greek philosophy of nature, which had dominated thinking about the universe for millennia. To embrace Copernicanism was to threaten Aristotelianism. The persistent requirement of fidelity to Aristotelianism had nothing to do with a Sun-centered system; rather, Aristotelianism was the basis for the philosophical and theological teachings of the time. If Aristotelian natural philosophy crumbled, some feared that the whole system of theology that it supported would also crumble.

In addition, the trial of Galileo occurred during the Thirty Years War, which entered a critical phase exactly at the time of the Galileo trial in 1632. The trial may have been a reaction to the political pressure being put on Pope Urban VIII by the Spanish (and others). By attacking Galileo, the Pope could be seen as showing the more conservative elements that he was not a radical. Perhaps also this was a veiled way of putting political pressure on the rich and powerful Medici family, who were Galileo’s patrons, to stay out of choosing sides in that war.

Did the Jesuits train Galileo?

We know that Galileo, as a young teacher at Pisa, relied upon notes of Jesuits, which he obtained from the Roman College (a Jesuit institution). The Jesuits taught the Aristotelian nature philosophy, which today we call physics, but they were also open to new scientific discoveries. Galileo was a good friend of some Jesuits, including the famous Jesuit mathematician and astronomer, Christopher Clavius. When Galileo’s first book, the “Starry Message,” was published, Jesuits at the Roman College held a special symposium in his honor. At the request of Cardinal Bellarmine, himself a Jesuit, the Jesuit scientists at the Roman College were the first to corroborate Galileo’s telescopic observations.

However, once he became famous with his writings, Galileo had a falling out with some Jesuits. This was driven at least in part by arguments of priority, as he felt that some Jesuit scientists who were publishing their own results about sunspots and comets were challenging his priority in these matters.

Was the Church anti-science in that time?

Not at all. Clergymen devoted a lot of their time to the study of the sciences even then. Many science books of that era were written by priests, such as Fr. Clavius (1538-1612) who was instrumental in the reform of the calendar, and Fr. Riccioli (1598-1671) who published the first modern map of the Moon and named craters on the Moon after Jesuits and other scientists, including Copernicus and Kepler.

What is the Church position now?

Even after the Galileo trial, the Copernican system was taught in Catholic schools; but it was presented as a mathematical system, not a philosophical description of the universe. By the mid 1700s, even that stricture was lifted, though Galileo’s books themselves were listed on the Index Librorum Prohibitorum (List of Prohibited Books) for another half century.

When Pope Leo XIII wrote on the importance of science and reason, he essentially embraced the philosophical principles put forth by Galileo, and many statements by Popes and the Church over the years have expressed admiration for Galileo. For example, Galileo was specifically singled out for praise by Pope Pius XII in his address to the International Astronomical Union in 1952.

Pope John Paul II named a commission to investigate again the Galileo affair; after the work of Galileo commission was completed, Pope John Paul II’s discourse to the Pontifical Academy of science in 1992 stated that Galileo’s sufferings at the hands of some individuals and church institutions were tragic and inescapable, and a consequence of a mutual incomprehension in those times between church theologians and the new scientists such as Galileo. To be clear, science as we know it was just being born and not even scientists of those times could comprehend fully what was happening. The Church officially apologized to Galileo in 2000. You can see Pope John Paul II’s discourse of 1992 at:


Was Galileo an atheist?

No, few people were in those days. In a private letter of Jan 20, 1610, Galileo writes: “I am infinitely grateful to God who has deigned to choose me alone to be the first to observe such marvelous things which have lain hidden for all ages past.” Galileo had two daughters, and both became religious sisters.