The Renaissance Mathematicus

The Galileo Circus is in town


The ‘sensational’ #histSTM news of last week was that a new ‘lost’/‘hidden’ Galileo letter has been discovered in the Royal Society archives. As some people have pointed out, as it was archived and catalogued it wasn’t exactly ‘lost’ or ‘hidden’, but that is not what I am going to write about here. As the Internet’s resident Galileo deflator, I have been asked numerous times in the last few days what I think is the significance of this find and my answer has been, not a lot. I have decided to explain why I think this but before I do so we need a bit of background for those not informed about the intricate details of Galileo’s biography.

Galileo Galilei portrait by Domenico Tintoretto Source: Wikimedia Commons

After the publication of his Sidereus Nuncius, Galileo was not only appointed court philosophicus and mathematicus the Cosimo De’ Medici but became almost over night the most notorious mathematical scholar in Europe. He was feted by the Northern Italian high society both secular and clerical and was definitely a celebrity. His role in the Medici household was not that dissimilar to that of a court jester. He was required to entertain the Grand Duke and his guests after dinner with his erudition and his wit. Oft opponents would be invited to dine and Galileo was expected to dispute with them over philosophical or scientific topics. In this role he acquitted himself extremely well but his growing fame and notoriety meant that he was collecting a solid body of enemies. On the subject of science contra religion his newly won high-powered friends and admirers advised him to tread carefully and to proceed with caution. Amongst those, who thus advised him, was Cardinal Maffeo Barberini an admirer and the future Pope Urban VIII.

C. 1598 painting of Maffeo Barberini at age 30 by Caravaggio Source: Wikimedia Commons

In 1613, in Galileo’s absence, at an evening round at the Medicean table the philosopher Cosimo Boscaglia stated that he thought that the telescopic discoveries were valid, however the Copernican hypothesis contradicted Holy Scripture. Galileo’s former student Benedetto Castelli, now a professor for mathematics and a Benedictine Abbott, defended Galileo’s standpoint under intensive questioning from Grand Duchess Christina, Cosimo’s mother and Galileo’s first patron in the Medici family. Castelli reported all of this to Galileo in a letter and in reply Galileo wrote a long essay, now known as the Letter to Castelli, in which he attacked the Church’s interpretation of the various Bible passages that stood in contradiction to the heliocentric hypothesis and generally pleaded for freedom of expression for science, or rather for Galileo.

Benedetto Castelli artist unknown Source: Wikimedia Commons

Before I go on I think it is necessary to restate something that people discussing the situation tend to forget or ignore. In the early seventeenth century the concepts of freedom of thought, freedom of speech and freedom of expression simply did not exist anywhere in Europe neither under secular or religious jurisdiction, no matter which church was involved. This was something that Galileo was well aware of but apparently in his hubris he thought his newly found fame would protect him from censure, he was wrong. A second point that also tends to get ignored is that when Galileo decided to go into full frontal attack with the Church on scriptural interpretation it was the middle of the Counter Reformation. The Reformation and the Counter Reformation centred on the question, who is allowed to interpret Holy Scripture. The Lutherans said anybody who could read, although they later changed their minds on that, whereas the Catholic Church said only the Church theologian were entitled to. Here was Galileo a mere mathematicus, the lowest of the low in the Renaissance intellectual hierarchy, telling the theologians, the pinnacle of the Renaissance intellectual pyramid, how to interpret the Bible, not a wise move. Not only did Galileo go out on a limb but he did so with his very best polemic and invective and if there was something in which Galileo was unrivalled at it was writing polemic and invective.

As was the custom in those days, and as Galileo certainly intended, copies were made of his letter and passed around for other to read and admire. It was almost inevitable that copies would land in the hands of his enemies and they were not in any way thrilled by Galileo’s attack on the Church.  In 1615 Niccolò Lorini, a Dominican, submitted a copy of Galileo’s letter to the Inquisition in Rome:

All our Fathers of the devout Convent of St. Mark feel that the letter contains many statements which seem presumptuous or suspect, as when it states that the words of Holy Scripture do not mean what they say; that in discussions about natural phenomena the authority of Scripture should rank last… [the followers of Galileo] were taking it upon themselves to expound the Holy Scripture according to their private lights and in a manner different from the common interpretation of the Fathers of the Church…

— Letter from Lorini to Cardinal Sfrondato, Inquisitor in Rome, 1615. Quoted in Jerome Langford, Galileo, Science and the Church1998, pp. 56-57 (Borrowed from Wikipedia)

Galileo, now realising that he might have not made the most intelligent move in his life, began to back peddle and claimed that the submitted document was not the letter that he had written but had been manipulated by his enemies to make it look worse than it really was. He also issued a new version of the letter that was indeed much milder than the version submitted to the Inquisition by Lorini. Things took their inevitable course. Galileo’s letter was lumped together with the Epistle concerning the mobility of the earth by Paolo Antonio Foscarini, which provoked the famous Foscarini Letter from Robert Bellarmino, which was also addressed to Galileo. The Inquisition decided that Copernicus’ theory was both scientifically and theologically unacceptable and Galileo had his famous meeting with Bellarmino, who explained that heliocentricity could not be taught as factual.

In this situation many, in fact the majority, see Galileo, as a champion for free speech and for the ascendency of science over religion, launching a brave attack on the bastions of the Church. I think it would be more honest to regard his actions as foolhardy, driven by hubris. One the one hand he thought that his celebrity was so great that he could successfully challenge the Church; he was severely mistaken. On the other he wanted to be the one feted for having ‘proved’ the heliocentric hypothesis. This is amply shown by the fact that as things started to turn pear-shaped he rushed off to Rome and tried to convince his admirers amongst the Church hierarchy of the validity of his theory of the tides, which would form the fourth and concluding day of his Dialogo. His hubris prevented him recognising just how flawed that infamous theory was. In 1615 he found no takers. It is interesting to note in terms of Galileo’s personality that at best he developed the theory of tides together with Paolo Sarpi and at worst it was actually Sarpi’s theory and he ‘borrowed’ it without in either case giving Sarpi any credit for the theory.

What the historian has to decide is was Galileo telling the truth and had his enemies in the Church manipulated his original letter or was he lying and was the letter submitted by Lorini the original document? Those who have written the numerous Galileo hagiographies believe that their hero was telling the truth. Others who are more sceptical about the Tuscan mathematicus don’t see him as a paragon of virtue but in this instance think that he was telling the truth and his Church enemies were out to get him. I, however, and I know that I am not alone in this opinion, think that he was lying and that the Lorini letter is in fact the original. Up till now there has been no proof either way, so you pays your money and you makes your choice.

The newly ‘discovered’ document is the proverbial smoking gun. It appears that it is the Letter to Castelli in the Lorini version with the ‘corrections’ to the later milder version all written in Galileo’s own hand. If the document is genuine, and I assume it is, then Galileo was without a shadow of a doubt lying. This of course provokes the question as to why I thought, without evidence, that he was indeed lying. The answer is very simple. As the old sergeant says in cheesy English criminal stories, “the lad had form, didn’t he?”

The original letter in which Galileo argued against the doctrine of the Roman Catholic Church has been rediscovered in London. Credit: The Royal Society

We start with Galileo’s claim that he constructed a telescope purely having heard of one based on his knowledge of optics. Modern research suggests very strongly that he had in fact both seen and handled a telescope before he constructed his own one. He also sold ‘his telescope’ to the Senate of Venice for a very high price, knowing full well that within a short time the city would be flooded with telescopes from other sources. Galileo had something of the character of the proverbial used car salesman. In his dispute with Christoph Scheiner about the nature of sunspots, Galileo kept changing the date he claimed to have first observed sunspots to guarantee his priority. Of course, both Galileo and Scheiner were unaware that Harriot had observed sunspots before both of them and Johannes Fabricius had already published on them. In 1607, charged Baldessar Capra with having plagiarised the instruction manual for his sector. At the time he exonerated Simon Marius who had been Capra’s mathematics teacher. However in 1623 in his Il Saggiatore he now falsely accused Marius of being responsible for the plagiarism along with accusing him again falsely of having plagiarised the Sidereus Nuncius in his Mundus Iovialis. In Il Saggiatore he also accused Scheiner falsely of having plagiarised his work on sunspots. To make the situation worse he quoted Scheiner’s work on sunspots as his own in the Dialogo. The main text of Il Saggiatore concerns his dispute with Grassi on the nature of comets. Here he brings his famous ‘the book of nature is written in the language of geometry’ quote implying that his point of view is mathematical/scientific whereas that of Grassi, a Jesuit, is not. Exactly the opposite is true. Grassi’s view that comets are supralunar was formed on the basis of empirical observations and mathematical calculations, whereas Galileo’s basically Aristotelian view was nothing but unsubstantiated and false speculation. In the Dialogo, the two world systems that Galileo compares are the geocentric system of Ptolemaeus and the heliocentric system of Copernicus. However when Galileo wrote his book the Ptolemaic system had already been refuted, as Galileo well knew having contributed to that refutation, and the Copernican system had long been superseded by the elliptical system of Kepler, which was regarded as a competing model. The world system being discussed as rivals at the time were a Tychonic model with diurnal rotation and Kepler’s elliptical heliocentric model both of which Galileo simply ignores. These are just some of the crassest examples of Galileo conscious dishonesty in his work. So believing that he lied about the Castelli letter is not an unreasonable assumption.

However, all in all, whether he lied or didn’t lie at this point in time doesn’t actually make that much difference. Whether his attack on Catholic theology was more or less vitriolic doesn’t actually play an important role is what happened. The important point is that he had the gall to launch that attack at all in such an undiplomatic manner. All that Galileo achieved by his ill thought out, impulsive actions was to delay quite substantially the Church’s inevitable acceptance of heliocentricity. Before somebody turns up in the comments saying it took them two hundred years to accept it, that acceptance already existed informally before the end of the seventeenth century and formally in 1758.