The Galileo Affair

What happened

Galileo Galilei (1564–1642) was an Italian astronomer, physicist, and mathematician who, in the early seventeenth century, gathered the first sustained body of telescopic observational evidence supporting the Copernican model of the solar system — the model in which the Earth and the other planets orbit the Sun, rather than the geocentric Ptolemaic model in which they orbit the Earth.

In 1616, the Roman Inquisition, advised by a theological commission convened by Pope Paul V, declared the proposition that the Sun is stationary at the centre of the universe "formally heretical." Cardinal Robert Bellarmine personally communicated this judgment to Galileo, instructing him not to hold or defend the Copernican view. Galileo agreed.

In 1632, Galileo published Dialogue Concerning the Two Chief World Systems (Dialogo sopra i due massimi sistemi del mondo), a Tuscan-language work in dialogue form that presented arguments for and against the two systems. The character defending the Ptolemaic system, Simplicio, presented arguments — including arguments that Pope Urban VIII had personally given to Galileo as the Pope's own — in a manner widely read as ridicule. The work received a Catholic imprimatur but was attacked at the papal court within months of publication.

In April 1633, the Inquisition opened a formal trial. The proceedings established (a) that Galileo had been instructed in 1616 not to hold or defend the Copernican view, and (b) that the Dialogue defended it. On 22 June 1633, the tribunal found Galileo "vehemently suspect of heresy"; required him to abjure, curse, and detest the Copernican view in a formal public ceremony; sentenced him to indefinite imprisonment (later commuted to house arrest); and placed the Dialogue on the Index Librorum Prohibitorum, where it remained until 1835.

Galileo spent the remainder of his life under house arrest, first at the archbishop's residence in Siena and then at his villa at Arcetri, where he died on 8 January 1642.

Subsequent acknowledgement

The Catholic Church's institutional rehabilitation of Galileo proceeded over several centuries: removal of Dialogue from the Index in 1835; publication of the trial documents in the late nineteenth century; the establishment of a papal commission in 1981 under John Paul II to re-examine the case; and the formal acknowledgement by John Paul II on 31 October 1992 that the theologians and tribunal of 1633 had made a "tragic mutual incomprehension" error in their treatment of Galileo and that the Copernican view did not in fact stand in opposition to Scripture properly read.

The 1992 statement is the institutional record of the Catholic Church's own acknowledgement of the historical error.

Significance

The Galileo affair is the founding case of the modern Western public's understanding of the conflict between institutional religious authority and empirical scientific inquiry. Its historical specifics — that the tribunal was responding in part to Galileo's perceived personal insult of the Pope, that the procedural ground of the conviction was disobedience to a 1616 injunction rather than heliocentrism as such, that Galileo himself remained a believing Catholic to the end of his life — are well-documented but do not alter the central institutional fact: the Catholic Church, exercising its highest doctrinal authority, condemned a true description of the physical world and held that condemnation for centuries.

Sources

• Maurice A. Finocchiaro, The Galileo Affair: A Documentary History (University of California Press, 1989). Translation of the trial documents.
• Maurice A. Finocchiaro, Retrying Galileo, 1633–1992 (University of California Press, 2005).
• John Paul II, address to the Pontifical Academy of Sciences, 31 October 1992 (text in L'Osservatore Romano, English weekly edition, 4 November 1992).
• Annibale Fantoli, Galileo: For Copernicanism and for the Church (Vatican Observatory Publications / University of Notre Dame Press, 1996).