Galileo was a devout Catholic, yet his writings on Copernican heliocentrism disturbed some in the Catholic Church, who believed in a geocentric model of the solar system. They argued that heliocentrism was in direct contradiction of the Bible (which is a questionable claim) and the highly revered ancient writings of Aristotle and Plato. For his insights, Galileo was threatened with death at the stake and would eventually face lifelong house arrest after recanting his claims.
The geocentric model was generally accepted at the time for several reasons. By the time of the controversy, the Catholic Church had largely abandoned the Ptolemaic model for the Tychonian model in which the Earth was at the centre of the Universe, the Sun revolved around the Earth and the other planets revolved around the Sun. This model is geometrically equivalent to the Copernican model and had the extra advantage that it predicted no parallax of the stars, an effect that was impossible to detect with the instruments of the time. In the view of Tycho and many others, this model explained the observable data of the time better than the geocentric model did. (That inference is valid, however, only on the assumption that no very small effect had been missed: that the instruments of the time were absolutely perfect, or that the Universe could not be much larger than was generally believed at the time. As to the latter, belief in the large, possibly infinite, size of the Universe was part of the heretical beliefs for which Giordano Bruno had been burned at the stake in 1600.)
An understanding of the controversies, if it is even possible, requires attention not only to the politics of religious organizations but to those of academic philosophy. Before Galileo had trouble with the Jesuits and before the Dominican friar Caccini denounced him from the pulpit, his employer heard him accused of contradicting Scripture by a professor of philosophy, Cosimo Boscaglia, who was neither a theologian nor a priest. The first to defend Galileo was a Benedictine abbot, Benedetto Castelli, who was also a professor of mathematics and a former student of Galileo's. It was this exchange that led Galileo to write the Letter to Grand Duchess Christina. (Castelli remained Galileo's friend, visiting him at Arcetri near the end of Galileo's life, after months of effort to get permission from the Inquisition to do so.)
However, real power lay with the Church, and Galileo's arguments were most fiercely fought on the religious level. The late nineteenth and early twentieth century historian Andrew Dickson White wrote from an anti-clerical perspective:
The war became more and more bitter. The Dominican Father Caccini preached a sermon from the text, "Ye men of Galilee, why stand ye gazing up into heaven?" and this wretched pun upon the great astronomer's name ushered in sharper weapons; for, before Caccini ended, he insisted that "geometry is of the devil," and that "mathematicians should be banished as the authors of all heresies." The Church authorities gave Caccini promotion.
Father Lorini proved that Galileo's doctrine was not only heretical but "atheistic," and besought the Inquisition to intervene. The Bishop of Fiesole screamed in rage against the Copernican system, publicly insulted Galileo, and denounced him to the Grand-Duke. The Archbishop of Pisa secretly sought to entrap Galileo and deliver him to the Inquisition at Rome. The Archbishop of Florence solemnly condemned the new doctrines as unscriptural; and Paul V, while petting Galileo, and inviting him as the greatest astronomer of the world to visit Rome, was secretly moving the Archbishop of Pisa to pick up evidence against the astronomer.
But by far the most terrible champion who now appeared was Cardinal Bellarmin, one of the greatest theologians the world has known. He was earnest, sincere, and learned, but insisted on making science conform to Scripture. The weapons which men of Bellarmin's stamp used were purely theological. They held up before the world the dreadful consequences which must result to Christian theology were the heavenly bodies proved to revolve about the Sun and not about the Earth. Their most tremendous dogmatic engine was the statement that "his pretended discovery vitiates the whole Christian plan of salvation." Father Lecazre declared "it casts suspicion on the doctrine of the incarnation." Others declared, "It upsets the whole basis of theology. If the Earth is a planet, and only one among several planets, it can not be that any such great things have been done specially for it as the Christian doctrine teaches. If there are other planets, since God makes nothing in vain, they must be inhabited; but how can their inhabitants be descended from Adam? How can they trace back their origin to Noah's ark? How can they have been redeemed by the Saviour?" Nor
was this argument confined to the theologians of the Roman Church; Melanchthon, Protestant as he was, had already used it in his attacks on Copernicus and his school. (White, 1898; online text)
In 1616, the Inquisition warned Galileo not to hold or defend the hypothesis asserted in Copernicus's On the Revolutions, though it has been debated whether he was admonished not to "teach in any way" the heliocentric theory. When Galileo was tried in 1633, the Inquisition was proceeding on the premise that he had been ordered not to teach it at all, based on a paper in the records from 1616; but Galileo produced a letter from Cardinal Bellarmine that showed only the "hold or defend" order. The latter is in Bellarmine's own hand and of unquestioned authenticity; the former is an unsigned copy, violating the Inquisition's own rule that the record of such an admonition had to be signed by all parties and notarized. Leaving aside technical rules of evidence, what can one conclude as to the real events? There are two schools of thought. According to Stillman Drake, the order not to teach was delivered unofficially and improperly; Bellarmine would not allow a formal record to be made, and assured Galileo in writing that the only order in effect was not to "defend or hold". According to Giorgio di Santillana, however, the unsigned minute was simply a fabrication by the Inquisition.
Despite his continued insistence that his work in the area was purely theoretical, despite his strict following of the church protocol for publication of works (which required prior examination by church censors and subsequent permission), and despite his close friendship with Maffeo Barberini who later became Pope Urban VIII and presided throughout the ordeal, Galileo was forced to recant his views repeatedly, and was put under house arrest from 1633 until his death in 1642.
The Roman Inquisition had rejected earlier pleas by Galileo to postpone or relocate the trial because of his ill health. At a meeting presided by Pope Urban VIII, the Inquisition decided to notify Galileo that he either had to come to Rome or that he would be arrested and brought there in chains. Galileo arrived in Rome for his trial before the Inquisition on February 13, 1633. After two weeks in quarantine, Galileo was detained at the comfortable residence of the Tuscan ambassador, as a favor to the influential Grand Duke Ferdinand II de' Medici. When the ambassador reported Galileo's arrival and asked how long the proceedings would be, the Pope replied that the Holy Office proceeded slowly, and was still in the process of preparing for the formal proceedings. In the event, having responded to the urgent demands of the Inquisition that he must report to Rome immediately, Galileo was laft to wait for two months before proceedings would begin.
On April 12, 1633, Galileo was brought to trial, and the formal interrogation by the Inquisition began. During this interrogation Galileo stated that he did not defend the Copernican theory, and cited a letter of Cardinal Bellarmine from Source | Copyright