VII.

Galileo’s Impact on Thought

The condemnation of Galileo did have some effect on universities and colleges in countries where the Catholic Church exercised control over teaching and publication, although the permission to treat Copernicanism as a useful, though false, calculating device meant that heliocentric (Sun-centered) ideas could always be made familiar to students. The ideas contained in the Dialogue could not be suppressed, and Galileo’s own scientific reputation remained high, both in Italy and abroad, especially after the publication of his final and greatest work.

Galileo’s final book, Discourses Concerning Two New Sciences, was published at Leiden in 1638. It reviews and refines his earlier studies of motion and, in general, the principles of mechanics. The book opened a road that was to lead Newton to the law of universal gravitation, which linked the planetary laws discovered by Galileo’s contemporary Johannes Kepler with Galileo’s mathematical physics. Galileo became blind before it was published, and he died at Arcetri, near Florence, on January 8, 1642.

Galileo’s most valuable scientific contribution was his part in transforming physics from a plausible framework erected on casual observations of complex everyday experiences into a method whereby selected experiences were so simplified that their underlying structures or patterns could be explained in geometrical terms and thus become susceptible to precise measurement. Galileo’s law of falling bodies, for example, disregards the resistance of the medium and concentrates solely on the relationship between distance fallen and time elapsed in a vacuum. If this simplified law proves to be only approximate, then the approach is repeated to find what refinement is needed to account for how an actual body falls through a medium—for example, through air. 

Galileo abandoned the key Aristotelian ideas according to which rest is a natural state and only motion needs explanation, and got so near to understanding the nature of inertial motion that Newton credited him with the discovery. More widely influential, however, were The Starry Messenger and Dialogue on the Two Chief World Systems, which opened new vistas in astronomy. Galileo was an outstanding popularizer of his own work and is recognized as a master of Italian prose. 

Galileo’s lifelong struggle to free scientific inquiry from restriction by philosophical and theological interference is also remembered as a major contribution to the development of science. Since the full publication of Galileo’s trial documents in the 1870s, entire responsibility for Galileo’s condemnation has customarily been placed on the officials of the Roman Catholic Church. A fuller picture would include the role of the professors of philosophy who first persuaded theologians to link Galileo’s science with heresy, although the responsibility for the ruling of 1616 and for the condemnation of Galileo must remain with the officials of the church and their advisers. 

An investigation into the astronomer’s condemnation was opened in 1979 by Pope John Paul II. A papal commission, set up in 1982, produced several scholarly publications related to the trial. In October 1992 the commission acknowledged the error of the church’s officials. In a speech accepting the report John Paul, alluding to Galileo’s views on scripture and science, said that Galileo, “a sincere believer, showed himself to be more perceptive in this regard than the theologians who opposed him.”