By JUDE DOUGHERTY
Finocchiaro, Maurice. The Trial of Galileo: Essential Documents, translated and edited by Maurice A. Finocchiaro. Indianapolis, IN: Hackett Publishing Co., 2014. Pp. xii+160.
This book draws upon Finocchiaro’s previously published works, The Galileo Affair: A Documentary History (1989) and Retrying Galileo: 1633-1992 (2005), at once making those masterful works more readily accessible, while adding some new material.
The narrative really begins with Copernicus, who in 1543 published his epoch-making On the Revolutions of Heavenly Spheres. The book updated an idea originally advanced in ancient Greece by the Pythagoreans and by Aristarchus of Samos — namely that the Earth rotates on its own axis daily and revolves around the sun yearly.
Copernicus advanced a new argument supporting an old idea, albeit a hypothetical one. It had the advantage of simplicity in accounting for the known movement of the heavenly bodies. It contradicted the physics or the science of motion at the time. Copernicus realized that his hypothesis did not prove the Earth’s motion, but his argument was so important that it could not be ignored.
Galileo, as a professor of mathematics at the University of Padua, did not embrace the Copernican view until 1609 when he became actively involved in astronomy. Until then he actually believed that the anti-Copernican arguments outweighed the supposed heliocentric view. But between 1609 and 1613 Galileo’s telescopic discoveries convinced him of the merit of the Copernican view.
His telescope had enabled him to make a series of startling discoveries. He found that a profusion of stars exists besides those available to the naked eye. He found that the Milky Way and the visible celestial nebulas are dense collections of a large number of individual stars. He also discovered that the planet Jupiter has four moons revolving about it at different distances with different periods.
Upon publication of these findings in his book, The Sidereal Messenger, Galileo became a celebrity. Soon after he also discovered the phases of Venus and the reality of sun spots. In 1613 he published the History and Demonstrations Concerning Sunspots. These discoveries substantially strengthened the case for Copernicanism.
Galileo’s discoveries did not settle the issue of the truth of the Copernican view of the earth’s motion, given that there was some astronomical counterevidence, mainly the failure to detect an annual stellar parallax, and because of the fact that the physics of a moving earth had not been explicitly articulated.
Above all there was the theological objection to a view that seemingly was incompatible with Sacred Scripture. Even though scientific arguments favored the geokinetic theory, they were inconclusive; the Earth’s motion remained a hypothesis. Galileo knew the difference between a hypothetical explanation and a demonstration.
Upon the publication of The Sidereal Messenger in 1610, Galileo was accused of heresy. The Congregation of the Holy Office commissioned a panel of 11 members to assess the charges. The panel unanimously found Galileo guilty of heresy.
Although that was the committee’s finding, churchmen were divided on the issue. Paolo Antonio Foscarini, a Carmelite friar, had published a book in 1615 arguing that the Earth’s motion was compatible with Sacred Scripture. Pope Urban VIII, an admirer of Galileo, apparently was not convinced of the incompatibility of the heliocentric theory and the Catholic faith and intervened to prevent Galileo from being charged with heresy.
Robert Cardinal Bellarmine, acting on behalf of the Holy Office, privately warned Galileo not to teach the Copernican view as having been established, and Galileo apparently agreed to comply. Previously Bellarmine had written to Foscarini that: “There is no danger in saying that by assuming the Earth moves and the sun stands still, one saves all the appearances better than by postulating eccentrics and epicycles, and that is sufficient for the mathematician.”
In part the dispute was about the nature of a hypothesis and its role in the search for truth. Is a hypothesis a mere instrument, a calculation, or observational prediction that can be more-or-less convenient, but neither true nor false, or whether a hypothesis is an assumption about physical reality that is more-or-less probable and potentially true or false but not yet known with certainty?
Galileo was right about the Earth’s movement, but he could not offer demonstrative evidence for his conclusion. Obviously the evaluation of his arguments must be regarded as a separate issue from his being right for his conclusion contradicted both a visual sense report and Sacred Scripture. His opponents demanded incontrovertible evidence.
Galileo’s further telescopic discoveries convinced him beyond all doubt that Copernicus was right, and given his temperament, Galileo could not remain silent. Galileo subsequently conceived a work that would discuss all aspects of the question and in 1632 published The Dialogue on the Two Chief World Systems: Ptolemaic and Copernican.
Vital Texts
With that publication, it was clear that he had come down on the side of Copernicus in violation of Bellarmine’s injunction. Hence the trial of 1633, in which Galileo was convicted of “vehement suspicion of heresy” and forbidden to promote the Copernican view in any form.
Always treated with great respect, he was never imprisoned nor did he suffer any physical harm, but he was sentenced to “house arrest” which he served in part while lodged in the Tuscan Embassy in Rome, the Palazzo Firenze, and later at the Villa Medici, and still later at the residence of the archbishop of Siena, and finally in his own home, where he died in 1642.
This short review cannot do justice to Finocchiaro’s informative study. Suffice it to say, anyone who dares to venture an opinion on what René Descartes called “L’affaire Galilée” must at least be familiar with the narrative and texts provided by Finocchiaro’s detailed studies.
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(Dr. Dougherty is dean emeritus of The School of Philosophy at The Catholic University of America.)
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