The Galileo Affair: A historical recap
Born in 1564, Galileo studied then taught mathematics at Pisa then Padua. As from 1610, he was the court mathematician of the Grand Duke of Tuscany[1], a position that enabled him fully to attend to his scientific research. Using spyglasses – an innovative instrument at the time, and which he claimed as his own invention – Galileo was able to observe new astronomical phenomena: 1) the moon was not flat and the sun had spots – so these celestial bodies were imperfect, which ran counter to Aristotelian philosophy[2]; 2)there existed celestial bodies that revolved neither around the earth nor the sun (e.g. Jupiter's moons); 3) the stars number was much larger than had been thought hitherto.
Against this background Galileo heard, in 1615, about the Foscarini affair. Paolo Antonio foscarini[3], a Carmelite monk, had published a book in which he sought to prove that the Copernician theory did not contradict the biblical text or its traditional interpretation regardless of all the sections mentioning solar movement. This book was instantly struck with inquisitorial[4] censorship and Roberto Bellarmino[5], one of the most influential cardinals at the time, instructed a trial against Foscarini. As an observer of these developments, Galileo wrote a letter to Christina of Lorraine[6], Grand-Duchess of Tuscany. This “Copernician letter” was not published until 1936 but it was already circulating in 1615 so that Galileo's position was already well known in some Italian circles. He mounted his defence of Foscarini and the Copernician system by offering a hermeneutics[7] wherein reason is as much a gift from God as the texts given as “revealed”, whence whatever does not pertain to the professed salvation of humanity can be determined by reason.
For Galileo, the question of which celestial body revolves around which belonged with what has no bearing on human salvation. Quite the reverse, it would be unwise to forbid the use of reason in this field for, he pointed out quoting Augustine of Hyppo[8], it could even damage Christianity's reputation. The waters were getting muddier and Foscarini's trial was hurried through. Galileo travelled to Rome to stop the banning of the Copernician theory but the trial had closed in 1616 on the censorship of Foscarini's book and the consignation to the Index of a few minor texts by Copernicus. The heliocentric system as such, however was not banned; it was acknowledged as a “mathematical model”. Galileo who was not personally affected by the bans, was requested in a letter addressed to him by Bellarmini, to teach the Copernician theory only as a hypothesis on the par with or inferior to Ptolemy's.
Over the following fifteen years, Galileo made no public statements regarding the Copernician theory, even though, in 1624, Pope Urban VIII[9] (who had been Galileo's student) invited him to do so, just as long as he presented it as a mere hypothesis. He was busy with other projects, notably a new, and no less contentious, atomist physics which kept some Jesuits[10] on the alert as they feared it might compromise the doctrine of transubstantiation[11]. With a poor health to boot, it is only in 1632 that Galileo published his Dialogue on the Two Chief World Systems. As suggested in the title of the work, Galileo confronts the heliocentric to the geocentric model in a dialogue form that enables him to appear to be defending both models whilst sheltering his heliocentric views behind one of the two fictitious participants in the dialogue. Unfortunately the presentation of both systems was far from being even-handed: Galileo's preferred view was conspicuously obvious not least through the name of Simplicio (simpleton) given to Ptolemy's champion; for good measure, Simplicio could be construed as a caricature of Urban.
The publication of this Dialogue was badly timed. In the context of the Thirty Years War[12], the pope sought a rapprochement with the Spanish party, represented in Rome by the Jesuits. Now in the eyes of the Society of Jesus, Galileo had long been suspected of heterodoxy. In 1633, Galileo was called before an inquisitorial court and found guilty of promoting the heliocentric system (which he only favoured) and of disobeying the 1616 “decision”, namely Bellarmino's private letter. This condemnation relied in the best of cases on debatable if not highly dubious facts essentially representative of the balance of power internal to the Catholic Church. Three out of the ten cardinals sitting failed to sign the sentence, modest though it was: after abjuring his errors Galileo was placed under house arrest. Against his commitment no longer to travel, Galileo obtained the right to pursue his research in mathematics and physics but not in astronomy.
