Saturday, February 20, 2010

Galileo's Trial: a battle between science and religion?

Post #3

So we have seen in posts one and two some corrections to a few common myths surrounding the Copernican Revolution. Geocentrism, for example, was not a Christian idea but a Greek one adopted by the church. Also, the contrast between geocentrism and heliocentrism, which was proposed by Copernicus, a devout Catholic, cannot be seen as a contrast between science and religion because Copernicus did not have any scientific evidence for his views.

Now we come to the main event: the trial of Galileo. This episode has come to symbolize the conflict between science and religion, specifically between the Christian church and Western science. My intent in this post is not to defend the medieval Christian church or its behavior. There are dark spots in the church’s history, and I have no interest in pretending otherwise. Rather, I intend to show what contemporary historians have discovered upon a closer look at the trial of Galileo: that it was a complicated affair that cannot be reduced to a battle between science and religion.


Galileo Galilei was an Italian philosopher and mathematician who was born in 1564 and passed away in 1642 at the age of 78. A full history of his life and interactions with the church is impossible in a blog post, but I wish to focus on a few important points.

First, Galileo was a brilliant philosopher and scientist, as well as a devout Catholic. He is rightly regarded as the father of experimental science, being among the first to insist on empirical work in scientific investigation rather than reasoning from first principles as was standard in universities at the time. Galileo’s brilliance and willingness to question accepted wisdom brought him both international acclaim and some enemies in the academic and religious establishments.

Galileo first garnered international acclaim through the publication, in 1610, of his book The Starry Messenger, which contained the newfound astronomical knowledge he gained through use of telescopes he designed himself. This new knowledge included the discovery of the four moons around Jupiter, new stars, and the fact that our Moon had craters and valleys. This last bit was interesting because within Aristotelian natural philosophy, then dominant, everything in the heavens was perfectly spherical and smooth. Galileo did not hesitate to proclaim these new discoveries, but some devoted Aristotelian academics refused to acknowledge his work (some even claimed that the images seen in Galileo’s telescopes were illusions or tricks).

Contrary to the impression one might get from the standard story, Galileo gathered many friends and admirers within the church. He was befriended by Father Clavius, a leading Jesuit astronomer and the chief mathematician of the Collego Romano, a church institution which endorsed Galileo’s work and joined him in studying the heavens. Even Pope Paul V and Cardinal Barberini (the future pope Urban VIII) became fans, and Barberini a personal friend, saying to Galileo, “I pray the Lord God to preserve you, because men of great value like you deserve to live a long time to the benefit of the public.”

It is worth noting here that there were many university academics who objected to Galileo’s work and many within the church who embraced it. There is more to the story here, but in short Galileo’s disregard for academic tradition (i.e. Aristotelianism) earned him some enemies within the academy and, eventually, in the church as well.

Science and Scripture

Copernicus’ book which proposed the heliocentric (sun-centered) theory, De Revolutionibus, had been published in 1543, some 60 years before Galileo’s Starry Messenger. The heliocentric theory had never caused an uproar; many academics and theologians thought it interesting, a few embraced it as literally true, and others ignored it. Part of the reason for this was that at the time mathematics and astronomy were considered to be concerned with “appearances.” For example, as long as an astronomical theory could, say, accurately predict the motions of stars and be useful to navigators, it did not matter whether the theory was physically true. Part of Galileo’s legacy would be to elevate mathematics and astronomy out of the realm of “appearances” and into natural philosophy proper. This change, however, was difficult for his contemporaries to accept.

Galileo had embraced the heliocentric theory by at least 1597, but it was after he became famous in 1610 that his views on the matter became more widely known. In both public dialogue and a few published letters, Galileo made clear his preference for Copernicus’ heliocentric theory over Ptolemy’s geocentric one. This became one point among many for sharp disagreement between Galileo and other prominent university academics. Galileo appears to have had a gift for making enemies, for he applied his brilliance not only to academic topics but also to decimating and humiliating those who publicly disagreed with him. Within the church, also, there began to emerge some people who thought Galileo to be a problem, a mathematician encroaching too far into the domain of the philosophers. A priest friend alerted Galileo that a “certain crowd…put their heads together in a mad quest for any means by which they could damage you.” For those within the church who disliked Galileo, his heliocentric leanings provided a good target for them to attack.

As we have seen, geocentrism was the dominant cosmology and had been for centuries. While there were exceptions, most people at this time thought that both natural philosophy (science) and scripture supported an earth-centered universe. Scriptural passages such as Psalm 19:4-6 and Joshua 10:12, where Joshua commands the Sun to hold still, were seen to support a stationary Earth. This idea, that Holy Scripture supports the Ptolemaic geocentric universe, would prove to be central in the trial of Galileo.

The Catholic Church at this time was recovering from the sudden loss of power and authority caused by the Protestant Reformation, which began in 1517. In 1545 the Council of Trent had declared, among other things, that only popes and bishops were allowed to interpret Scripture. Galileo’s enemies, then, could cast his espousing the heliocentric theory as being against Holy Scripture. They did exactly that, and attracted the attention of the Pope, who ordered Cardinal Bellarmino, an important Jesuit intellectual, to look into whether Copernicanism might be heretical. Bellarmino was an admirer of Galileo’s work, but was skeptical of heliocentrism and believed that it did contradict scripture. The Catholic Church had a long history of distinguishing between literal and figurative language in the Bible, but, due to the Reformation and the Council of Trent, Bellarmino was obliged to defend the current interpretation of the church fathers. The Catholic Church was in an extraordinarily defensive frame of mind, and in the words of historian Richard Blackwell, “[I]t was in no mood to adopt a new and revolutionary model of the heavens.”

This was especially true since neither Copernicus nor Galileo had offered clear evidence for their views. Galileo went to Rome to argue his case, but his main piece of evidence was an erroneous theory of his about the cause of the tides. His other astronomical observations cast doubt on some of Aristotle’s claims about the heavens (e.g. their immutability) but failed to comment on the truth of the heliocentric versus geocentric theories. Since both natural philosophy and scripture appeared to support geocentrism, Bellarmino sided with tradition, seeing no good reason to do otherwise. In March of 1616 a formal proclamation was issued, declaring the Copernican position to be “false and contrary to Holy Scripture” and De Revolutionibus was ordered to have a few passages “corrected.” Bellarmino had a private meeting with Galileo to give him a warning to only treat Copernicanism as a hypothesis, but did not put any restrictions on his published works.

Gossip and rumors spread by Galileo’s enemies suggested that Galileo had been denounced and forced to repent, but Cardinal Bellarmino wrote a public letter declaring otherwise, and the Pope even met with Galileo to assure him that he had their full support against his slanderers. Even so, Galileo took the warning seriously (as the Church had meant it seriously) and was quiet for many years in his public affairs concerning the arrangement of the universe.

Next Post: Galileo's Trial

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