Without a doubt the most well-known, in fact notorious, episode in the transition from a geocentric to a heliocentric cosmology/astronomy in the seventeenth century was the publication of Galileo Galilei’s Dialogo sopra i due massimi sistemi del mondo (Dialogue Concerning the Two Chief World Systems) in 1632 and his subsequent trial and conviction by the Supreme Sacred Congregation of the Roman and Universal Inquisition or simply Roman Inquisition; an episode that has been blown up out of all proportions over the centuries. It would require a whole book of its own to really do this subject justice but I shall deal with it here in two sketches. The first to outline how and why the publication of this book led to Galileo’s trial and the second to assess the impact of the book on the seventeenth century astronomical/cosmological debate, which was much less than is often claimed.
The first salient point is Galileo’s social status in the early seventeenth century. Nowadays we place ‘great scientists’ on a pedestal and accord them a very high social status but this was not always the case. In the Renaissance, within society in general, natural philosophers and mathematicians had a comparatively low status and within the ruling political and religious hierarchies Galileo was effectively a nobody. Yes, he was famous for his telescopic discoveries but this did not change the fact that he was a mere mathematicus. As court mathematicus and philosophicus to the Medici in Florence he was little more than a high-level court jester, he should reflect positively on his masters. His role was to entertain the grand duke and his guests at banquets and other social occasions with his sparkling wit, either in the form of a discourse or if a suitable opponent was at hand, in a staged dispute. Points were awarded not for truth content but for verbal brilliance. Galileo was a master at such games. However, his real status as a courtier was very low and should he bring negative attention to the court, they would drop him without a thought, as they did when the Inquisition moved against him.
As a cardinal, Maffeo Barberini (1568–1644) had befriended Galileo when his first came to prominence in 1611 and he was also an admirer of the Accademia dei Lincei. When he was elected Pope in 1623 the Accademia celebrated his election and amongst other things presented him with a copy of Galileo’s Il Saggiatore, which he read and apparently very much enjoyed. As a result he granted Galileo several private audiences, a great honour. Through his actions Barberini had raised Galileo to the status of papal favourite, a situation not without its dangers.
Mario Biagioli presents the, I think correct, hypothesis that having raised Galileo up as a court favourite Barberini then destroyed him. Such behaviour was quite common under absolutist rulers, as a power demonstration to intimidate potential rebels. Galileo was a perfect victim for such a demonstration highly prominent and popular but with no real political or religious significance. Would Barberini have staged such a demonstration at the time? There is evidence that he was growing more and more paranoid during this period. Barberini, who believed deeply in astrology, heard rumours that an astrologer had foreseen his death in the stars. His death was to coincide with a solar eclipse in 1630. Barberini with the help of his court astrologer, Tommaso Campanella (1568–1639) took extreme evasive action and survived the cosmic threat but he had Orazio Morandi (c. 1570–1630), a close friend and supporter of Galileo’s, arrested and thrown in the papal dungeons, where he died, for having cast the offending horoscope.
Turning to the Dialogo, the official bone of contention, Galileo succeeded in his egotism in alienating Barberini with its publication. Apparently during the phase when he was very much in Barberini’s good books, Galileo had told the Pope that the Protestants were laughing at the Catholics because they didn’t understand the heliocentric hypothesis. Of course, during the Thirty Years War any such mockery was totally unacceptable. Barberini gave Galileo permission to write a book presenting and contrasting the heliocentric and geocentric systems but with certain conditions. Both systems were to be presented as equals with no attempts to prove the superiority or truth of either and Galileo was to include the philosophical and theological opinion of the Pope that whatever the empirical evidence might suggest, God in his infinite wisdom could create the cosmos in what ever way he chose.
The book that Galileo wrote in no way fulfilled the condition stated by Barberini. Presented as a discussion over four days between on the one side a Copernican, Salviati named after Filippo Salviati (1682–1614) a close friend of Galileo’s and Sagredo, supposedly neutral but leaning strongly to heliocentricity, named after Giovanni Francesco Sagredo (1571–1620) another close friend of Galileo’s. Opposing these learned gentlemen is Simplicio, an Aristotelian, named after Simplicius of Cilicia a sixth-century commentator on Aristotle. This name is with relative certainty a play on the Italian word “semplice”, which means simple as in simple minded. Galileo stacked the deck from the beginning.
The first three days of discussion are a rehash of the previous decades of discoveries and developments in astronomy and cosmology with the arguments for heliocentricity, or rather against geocentricity in its Ptolemaic/Aristotelian form, presented in their best light and the counter arguments presented decidedly less well. Galileo was leaving nothing to chance, he knew who was going to win this discussion. The whole thing is crowned with Galileo’s theory of the tides on day four, which he falsely believed, despite its very obvious flaws, to be a solid empirical proof of the Earth’s movements in a heliocentric model. This was in no way an unbiased presentation of two equal systems but an obvious propaganda text for heliocentricity. Worse than this, he placed the Pope’s words on the subject in the mouth of Simplicio, the simpleton, not a smart move. When it was published the shit hit the fan.
However, before considering the events leading up to the trial and the trial itself there are a couple of other factors that prejudiced the case against Galileo. In order to get published at all, the book, as with every other book, had to be given publication permission by the censor. To repeat something that people tend to forget, censorship was practiced by all secular and all religious authorities throughout the whole of Europe and was not peculiar to the Catholic Church. Freedom of speech and freedom of thought were alien concepts in the world of seventeenth century religion and politics. Galileo wanted initially to title the book, Dialogue on the Ebb and Flow of the Seas, referring of course to his theory of the tides, and include a preface to this effect. He was told to remove both by the censor, as they, of course, implied a proof of heliocentricity. Because of an outbreak of the plague, Galileo retired to Florence to write his book and preceded to play the censor in Florence and the censor in Rome off against each other, which meant that the book was published without being properly controlled by a censor. This, of course, all came out after publication and did not help Galileo’s case at all; he had been far too clever for his own good.
Another major problem had specifically nothing to do with Galileo in the first instance but rebounded on him at the worst time. On 8 March 1632 Cardinal Borgia castigated the Pope for not supporting King Philipp IV of Spain against the German Protestants. The situation almost degenerated into a punch up with the Swiss Guard being called in to separate the adversaries. As a result Barberini decided to purge the Vatican of pro-Spanish elements. One of the most prominent men to be banished was Giovanni Ciampoli (1589–1643) Barberini’s chamberlain. Ciampoli was an old friend and supporter of Galileo and a member of the Accademia dei Lincei. He was highly active in helping Galileo trick the censors and had read the manuscript of the Dialogo, telling Barberini that it fulfilled his conditions. His banishment was a major disaster for Galileo.
One should of course also not forget that Galileo had effectively destroyed any hope of support from the Jesuits, the leading astronomers and mathematicians of the age, who had very actively supported him in 1611, with his unwarranted and libellous attacks on Grazi and Scheiner in his Il Saggiatore. He repeated the attacks on Scheiner in the Dialogo, whilst at the same time plagiarising him, claiming some of Scheiner’s sunspot discoveries as his own. There is even some evidence that the Jesuits worked behind the scenes urging the Pope to put Galileo on trial.
When the Dialogo was published it immediately caused a major stir. Barberini appointed officials to read and assess it. Their judgement was conclusive, the Dialogo obviously breached the judgement of 1616 forbidding the teaching of heliocentricity as a factual theory. Anybody reading the Dialogo today would confirm that judgement. The consequence was that Galileo was summoned to Rome to answer to the Inquisition. Galileo stalled claiming bad health but was informed either he comes or he would be fetched. The Medici’s refused to support him; they did no consider him worth going into confrontation with the Pope for.
We don’t need to go into details of the trial. Like all authoritarian courts the Inquisition didn’t wish to try their accused but preferred them to confess, this was the case with Galileo. During his interviews with the Inquisition Galileo was treated with care and consideration because of his age and bad health. He was provided with an apartment in the Inquisition building with servants to care for him. At first he denied the charges but when he realised that this wouldn’t work he said that he had got carried away whilst writing and he offered to rewrite the book. This also didn’t work, the book was already on the market and was a comparative best seller, there was no going back. Galileo thought he possessed a get out of jail free card. In 1616, after he had been interviewed by Bellarmino, rumours circulated that he had been formally censured by the Inquisition. Galileo wrote to Bellarmino complaining and the Cardinal provided him with a letter stating categorically that this was not the case. Galileo now produced this letter thinking it would absolve him of the charges. The Inquisition now produced the written version of the statement that had been read to Galileo by an official of the Inquisition immediately following his interview with Bellarmino expressly forbidding the teaching of the heliocentric theory as fact. This document still exists and there have been discussions as to its genuineness but the general consensus is that it is genuine and not a forgery. Galileo was finished, guilty as charged. Some opponents of the Church make a lot of noise about Galileo being shown the instruments of torture but this was a mere formality in a heresy trial and at no point was Galileo threatened with torture.
The rest is history. Galileo confessed and formally adjured to the charge of grave suspicion of heresy, compared to heresy a comparatively minor charge. He was sentenced to prison, which was immediately commuted to house arrest. He spent the first months of his house arrest as the guest of Ascanio II Piccolomini (1590–1671), Archbishop of Siena,
until Barberini intervened and sent him home to his villa in Arcetri. Here he lived out his last decade in comparative comfort, cared for by loyal servants, receiving visitor and writing his most important book, Discorsi e dimostrazioni matematiche intorno a due nuove scienze (Discourses and Mathematical Demonstrations Relating to Two New Sciences).
Galileo’s real crime was hubris, trying to play an absolutist ruler, the Pope, for a fool. Others were executed for less in the seventeenth century and not just by the Catholic Church. Galileo got off comparatively lightly.
What role did the Dialogo actually play in the ongoing cosmological/astronomical debate in the seventeenth century? The real answer is, given its reputation, surprisingly little. In reality Galileo was totally out of step with the actual debate that was taking place around 1630. Driven by his egotistical desire to be the man, who proved the truth of heliocentricity, he deliberately turned a blind eye to the most important developments and so side lined himself.
We saw earlier that around 1613 there were more that a half a dozen systems vying for a place in the debate, however by 1630 nearly all of the systems had been eliminated leaving just two in serious consideration. Galileo called his book Dialogue Concerning the Two Chief World Systems, but the two systems that he chose to discuss, the Ptolemaic/Aristotelian geocentric system and the Copernican heliocentric system, were ones that had already been rejected by almost all participants in the debate by 1630 . The choice of the pure geocentric system of Ptolemaeus was particularly disingenuous, as Galileo had helped to show that it was no longer viable twenty years earlier. The first system actually under discussion when Galileo published his book was a Tychonic geo-heliocentric system with diurnal rotation, Christen Longomontanus (1562–1647), Tycho’s chief assistant, had published an updated version based on Tycho’s data in his Astronomia Danica in 1622. This was the system that had been formally adopted by the Jesuits.
The second was the elliptical heliocentric system of Johannes Kepler, of which I dealt with the relevant publications in the last post.
Galileo completely ignores Tycho, whose system could explain all of the available evidence for heliocentricity, because he didn’t want to admit that this was the case, arguing instead that the evidence must imply a heliocentric system. He also, against all the available empirical evidence, maintained his belief that comets were sublunar meteorological phenomena, because the supporters of a Tychonic system used their perceived solar orbit as an argument for their system. He is even intensely disrespectful to Tycho in the Dialogo, for which Kepler severely castigated him. He also completely ignores Kepler, which is even more crass, as the best available arguments for heliocentricity were to be found clearly in Kepler published works. Galileo could not adopt Kepler’s system because it would mean that Kepler and not he would be the man, who proved the truth of the heliocentric system.
Although the first three days of the Dialogo provide a good polemic presentation for all of the evidence up till that point for a refutation of the Ptolemaic/Aristotelian system, with the very notable exception of the comets, Galileo’s book was out dated when it was written and had very little impact on the subsequent astronomical/cosmological debate in the seventeenth century. I will indulge in a little bit of hypothetical historical speculation here. If Galileo had actually written a balanced and neutral account of the positive and negative points of the Tychonic geo-heliocentric system with diurnal rotation and Kepler’s elliptical heliocentric system, it might have had the following consequences. Firstly, given his preeminent skills as a science communicator, his book would have been a valuable contribution to the ongoing debate and secondly he probably wouldn’t have been persecuted by the Catholic Church. However, one can’t turn back the clock and undo what has already been done.
I will close this overlong post with a few brief comments on the impact of the Church’s ban on the heliocentric theory, the heliocentric hypothesis was still permitted, and the trial and sentencing of Galileo, after all he was the most famous astronomer in Europe. Basically the impact was much more minimal than is usually implied in all the popular presentations of the subject. Outside of Italy these actions of the Church had almost no impact whatsoever, even in other Catholic countries. In fact a Latin edition of the Dialogo was published openly in Lyon in 1641, by the bookseller Jean-Antoine Huguetan (1567–1650), and dedicated to the French diplomat Balthasar de Monconys (1611–1665), who was educated by the Jesuits.
Within Italy well-behaved Catholics censored their copies of Copernicus’ De revolutionibus according to the Church’s instructions but continued to read and use them. Censored copies of the book are virtually unknown outside of Italy. Also within Italy, astronomers would begin their discussions of heliocentricity by stating in the preface that the Holy Mother Church in its wisdom had declared this system to be false, but it is an interesting mathematical hypothesis and then go on in their books to discuss it fully. On the whole the Inquisition left them in peace.
***A brief footnote to the above: this is a historical sketch of what took place around 1630 in Northern Italy written from the viewpoint of the politics, laws and customs that ruled there at that time. It is not a moral judgement on the behaviour of either the Catholic Church or Galileo Galilei and I would be grateful if any commentators on this post would confine themselves to the contextual historical facts and not go off on wild moral polemics based on hindsight. Comments on and criticism of the historical context and/or content are, as always, welcome.