The Galileo Fallacy

John Harney
Magonia 21, December 1985

We all agree, don’t we, that Christians in general, and Catholics in particular, ought to cringe at the name of Galileo, because of the way he was treated by the Church. Galileo, as we all know, was persecuted by the Church, and attempts were made to suppress his theories and discoveries because of the stupidity, ignorance and general fat-headedness of the Pope and his henchmen. This is more or less the generally accepted view, but is it true?

Actually, it is a view which conveniently ignores the facts of the case. Galileo’s troubles with the Church were largely self inflicted, as I shall attempt to show, beginning with the background to the case.

The development of Christian thought was strongly influenced by Greek philosophy, to the extent that the Church Fathers had adapted their interpretation of the Bible to fit in with the Aristotelian world picture. The basic principle of this picture was that the Earth was stationary at the centre of the universe and that the Sun, Moon and planets revolved around it with uniform, circular motions. Surrounding them was the sphere holding the fixed stars which had a daily rotation and which bounded the universe. This, together with other notions concerning the nature of the universe, became inextricably entwined with Christian thought to the extent that it came to be generally believed that they were confirmed by Scripture, if properly interpreted. In 1546 the Council of Trent decreed that the general consensus of the Church Fathers should not be deviated from when interpreting Scripture.

Although astronomy was profoundly influenced by the Aristotelian world picture, the astronomers did not feel that they were entirely bound by it. Theirs was a practical art which had as its main purpose the prediction of astronomical events for astrological use, for adjusting calendars, and for navigation. The observed motions of the planets did not fit in with the accepted cosmological model and the astronomers had various mathematical devices by which they manipulated the conventional model in ways which made their calculations less cumbersome. Nicolaus Copernicus (1473-1543) was an astronomer who was not content with mere mathematical devices, and he devised a Sun-centred system which he believed to be a true picture of the universe. He attempted to forestall criticism by pointing out that he had restored the principle of uniform, circular motion and by arguing that the stars were so far away the Earth was practically at the centre of the universe anyway.
Although Copernicus[left]  published his theory in 1543 it did not lead to any serious conflict with the Church until Galileo began to make a name for himself.

Galileo Galileo (1564-1642) was a mathematician who supported the Copernican theory. He too wanted a theory which gave a true picture of the universe and he believed that he had found this in the theory devised by Copernicus. Not content with convincing himself he was determined to publicise and defend his theory until it became generally accepted and he expressed his arguments in a forceful manner.

He first became widely know as the result of publishing a book called The Starry Messenger in 1610. In this he argued against the Aristotelian system and in favour of Copernicus, and supported his arguments with accounts of his observations with the recently invented telescope. He described the Moon’s craters and mountains and thus disposed of the classical idea that all the heavenly bodies had perfectly smooth surfaces.

He also presented other material which discredited the Aristotelian system. However, and this is an important point, he did not prove the correctness of the Copernican theory. Tycho Brahe’s alternative hypothesis was available, and according to this the Earth was at the centre of the universe with the Moon revolving around it, and further out the Sun also revolving around the Earth, with Mercury, Venus, Mars, Jupiter and Saturn revolving around the Sun. Galileo never got around to refuting this theory; he simply did not accept it, although it was not logically inconsistent with his observations.

If Galileo could not disprove an alternative hypothesis it thus followed that he could not prove the Copernican theory or even demonstrate that it was the most plausible model of the universe of those that had been devised up to that time. Another important point about the theory which was not emphasised by Galileo was that it could not be squared with accurate observations of planetary motions without introducing a complicated system of epicycles. He does not seem to have considered Kepler’s simplifying assumption that the planetary orbits were elliptical because he was, like Copernicus, strongly attached to the principle of uniform circular motion.

Galileo was first in trouble with the university professors who were naturally appalled at the prospect that the Aristotelian cosmology they were teaching might be dismissed as nonsense and rapidly replaced by a radically different model of the universe, which would make them look rather foolish. Those of them that claimed that his observations were illusory did have a point though. Galileo’s telescopes were very crude compared to modern instruments and it is hard to believe, for instance, that an uneducated eye would clearly see the phases of Venus through them. The observers would have to know what they were looking for to make any sense of the tiny blurred images presented to their gaze. Even with a modern small telescope it is difficult to see Venus clearly, because of the dazzling brightness of the planet.

However, when Galileo visited Rome in 1611 he had a very friendly reception from Pope Paul V. The Jesuits favoured intellectual pursuits and their authority on astronomy, Father Clavius, had informed Cardinal Bellarmine, head of the Roman College, that he could confirm that Galileo’s telescopic observations were genuine.

At this point we may ask if Galileo could have avoided his eventual conviction of heresy and his humiliating recantation. Almost certainly he could have. There is no reason why he should have become involved in any serious quarrel with the Church had he been more circumspect and had he only realised that he was unwittingly forcing the Church authorities into a position where they would have to take decisive action on the matter. Certainly, Galileo had enemies, but this is the lot of all persons who become well-known. He also had many influential friends in the Church; after all, he was a Catholic and as much a member of the Church as any other. Also an increasing number of natural philosophers in the Church were gradually coming to realise that Aristotelian cosmology was becoming untenable.

As for Galileo’s enemies, there is evidence that they were not taken very seriously by the Church. Lodovico delle Colombe organised opposition to Galileo, and one of his methods was to try to persuade priests to preach sermons against Copernicanism. (Colombe’s supporters were known as the ‘pigeon league’ because Colombe is the Italian word for dove.) Colombe’s men influenced the Dominican Father Caccini, who preached a sermon in somewhat immoderate terms, against Galileo, Copernicanism and mathematicians in general, accusing them of being enemies of Christianity. The important point about this incident is that Caccini’s outburst was firmly disowned by the Church. The Master-General of the Dominican Order wrote to Galileo to apologise for it. The opposition of the ‘pigeon league’ and its clerical supporters was not to be taken too seriously; we must look elsewhere for the real causes of Galileo’s tribulations.

The real causes, I suggest were Galileo’s own argumentative character, the relative weakness of the arguments with which he attempted to bolster the Copernican theory and, above all, his forcefully expressed views on the correct interpretation of Scripture with respect to scientific matters.

It is customary to look at the controversy from Galileo’s point of view. However for the Church’s point of view there were a number of practical considerations and these were clearly expressed in a letter which Cardinal Ballarmine wrote in reply to the Carmelite friar, Paolo Foscarini, who had sent him a copy of his book which asserted that the Copernican system was literally true. Ballarmine pointed out that acceptance of the idea of a sun-centred universe as being literally true would not only irritate the theologians and scholastic philosophers, but would injure the faith of many by making the Bible appear to be false, bearing in mind the interpretation of the Bible agreed by the Church Fathers and endorsed by the Council of Trent. He agreed that the Scriptures would need to be reinterpreted if the truth of the Copernican system could be demonstrated, but pointed out that such proof had not yet been forthcoming.

Pope Urban VIII
was an admirer of Galileo's work

Galileo, apparently insensitive to such considerations, went to Rome in 1615 and debated his cause so energetically that Pope Paul V felt the need to request an official statement on the matter from the Congregation of the Index. Not surprisingly their judgement confirmed the established teachings of the Church. Galileo tried again in 1624, hoping that the election the previous year of Maffeo Barberini as Pope Urban VIII might have made the climate more favourable to his views, as Barberini was an admirer of Galileo’s work. However, he found that the new Pope upheld the same attitude and Galileo was again told that he was quite free to discuss his ideas, provided he made it quite clear that they were mere hypothesis, and did not purport to give a true picture of the universe.

Again, he failed to take the advice, and finally went too far, so far as the Pope and his advisers were concerned, in his book Dialogue Concerning the Two Principle Systems of the World. In this, by the use of irony, he insinuated that the Church’s attitude was based on foolishness and ignorance. It was typical of him that he obeyed the summons to Rome to be tried by the Inquisition, instead of taking up an offer of asylum in Venice, presumably still determined to convert the Church to his way of thinking.

Perhaps his greatest error was to see that one of his major arguments worked both ways. He argued that the authors of the Bible accommodated their writings to everyday speech and common beliefs in order to put their religious message in a manner understandable to all, yet he failed to realise that the Church had to do the same to express its teachings in terms that could be understood by ordinary people, and not just by philosophers and intellectuals. The Popes and others in the Church who bore heavy responsibilities for the spiritual welfare of millions were obviously aware of this. They realised that any sudden change in the Church’s teaching would cause great harm by throwing the faithful into confusion. They were also no doubt aware that it would be very rash to make such drastic changes to accommodate a scientific theory which might. yet be shown to be false and be superseded by yet another theory.

Had Galileo realised this, and taken the Church’s advise, then perhaps the new astronomy could have gradually and painlessly taken hold of popular awareness and the cosmology of Aristotle would have died a natural death.