Galileo on Nature, Scripture, and Truth
One of the clearest statements of Galileo's convictions about religion and science comes from his 1615 letter to the grand duchess Christina, mother of Galileo's patron, Cosimo de' Medici, and a powerful figure in her own right. Galileo knew that others objected to his work. The church had warned him that Copernicanism was inaccurate and impious; it could be disproved scientifically, and it contradicted the authority of those who interpreted the Bible. Thoroughly dependent on the Medicis for support, he wrote to the grand duchess to explain his position. In this section of the letter, Galileo sets out his understanding of the parallel but distinct roles of the Church and natural philosophers. He walks a fine line between acknowledging the authority of the Church and standing firm in his convictions.
Ossibly because they are disturbed by the known truth of other propositions of mine which differ from those commonly held, and therefore mistrusting their defense so long as they confine themselves to the field of philosophy, these men have resolved to fabricate a shield for their fallacies out of the mantle of pretended religion and the authority of the Bible. . . .
Copernicus never discusses matters of religion or faith, nor does he use arguments that depend in any way upon the authority of sacred writings which he might have interpreted erroneously. He stands always upon physical conclusions pertaining to the celestial motions, and deals with them by astronomical and geometrical demonstrations, founded primarily upon sense experiences and very exact observations. He did not ignore the Bible, but he knew very well that if his doctrine were proved, then it could not contradict the Scriptures when they were rightly understood. . . .
I think that in discussions of physical problems we ought to begin not from the authority of scriptural passages, but from sense-experiences and necessary demonstrations; for the holy Bible and the phenomena of nature proceed alike from the divine Word, the former as the dictate of the Holy Ghost and the latter as the observant executrix of God's commands. It is necessary for the Bible, in order to be accommodated to the understanding of every man, to speak many things which appear to differ from the absolute truth so far as the bare meaning of the words is concerned. But Nature, on the other hand, is inexorable and immutable; she never transgresses the laws imposed upon her, or cares a whit whether her abstruse reasons and methods of operation are understandable to men. For that reason it appears that nothing physical which sense-experience sets before our eyes, or which necessary demonstrations prove to us, ought to be called in question (much less condemned) upon the testimony of biblical passages which may have some different meaning beneath their words. For the Bible is not chained in every expression to conditions as strict as those which govern all physical effects; nor is God any less excellently revealed in Nature's actions than in the sacred statements of the Bible. . . .
Source: Galileo, "Letter to the Grand Duchess Christina," in The Discoveries and Opinions of Galileo Galilei, ed. Stillman Drake (Garden City, NY: 1957), pp. 177-83.
Questions for Analysis
1. How does Galileo deal with the contradictions between the evidence of his senses and biblical teachings?
2. For Galileo, what is the relationship between God, man, and nature?
3. Why did Galileo need to defend his views in a letter to Christina de' Medici?
For a while, he did as he was asked. But when his Florentine friend and admirer Maffeo Barberini was elected pope as Urban VIII in 1623, Galileo believed the door to Copernicanism was (at least half) open. He drafted one of his most famous works, A Dialogue Concerning the Two Chief World Systems published in 1632. The Dialogue was a hypothetical debate between supporters of the old Ptolemaic system, represented by a character he named Simplicio (simpleton), on the one hand, and proponents of the new astronomy, on the other. Throughout, Galileo gave the best lines to the Coper-nicans. At the very end, however, to satisfy the letter of the Inquisition’s decree, he had them capitulate to Simplicio.
The Inquisition banned the Dialogue and ordered Galileo to stand trial in 1633. Pope Urban, provoked by Galileo’s scorn and needing support from Church conservatives during a difficult stretch of the Thirty Years’ War, refused to protect his former friend. The verdict of the secret trial shocked Europe. The Inquisition forced Galileo to repent his Copernican position, banned him from working on or even discussing Copernican ideas, and placed him under house arrest for life. According to a story that began to circulate shortly afterward, as he left the court for house arrest he stamped his foot and muttered defiantly, looking down at the earth: “Still, it moves.”
The Inquisition could not put Galileo off his life’s work. He refined the theories of motion he had begun to develop early in his career. He proposed an early version of the theory of inertia, which held that an object’s motion stays the same until an outside force changed it. He calculated that objects of different weights fall at almost the same speed and with a uniform acceleration. He argued that the motion of objects follows regular mathematical laws. The same laws that govern the motions of objects on earth (which could be observed in experiments) could also be observed in the heavens—again a direct contradiction of Aristotelian principles and an important step toward a coherent physics based on a sun-centered model of the universe. Compiled under the title Two New Sciences (1638), this work was smuggled out of Italy and published in Protestant Holland.
Among Galileo’s legacies, however, was exactly the rift between religion and science that he had hoped to avoid. Galileo believed that Copernicanism and natural philosophy in general need not subvert theological truths, religious belief, or the authority of the Church. But his trial seemed to show the contrary, that natural philosophy and Church authority could not coexist. Galileo’s trial silenced Copernican voices in southern Europe, and the Church’s leadership retreated into conservative reaction. It was therefore in northwest Europe that the new philosophy Galileo had championed would flourish.
As the practice of the new sciences became concentrated in Protestant northwest Europe, new thinkers began to spell out standards of practice and evidence. Sir Francis Bacon and Rene Descartes (deh-KAHRT) loomed especially large in this development, setting out methods or the rules that should govern modern science. Bacon (1561-1626) lived at roughly the same time as Kepler and Galileo—and Shakespeare; Descartes (1596-1650) was slightly younger. Both Bacon and Descartes came to believe that theirs was an age of profound change, open to the possibility of astonishing discovery. Both were persuaded that knowledge could take the European moderns beyond the ancient authorities. Both set out to formulate a philosophy to encompass the learning of their age.
FRONTISPIECE TO BACON'S NOVUM ORGANUM (1620).
The illustration suggests that scientific work is like a voyage of discovery, similar to a ship setting out through uncharted waters. Is it a voyage of conquest? Compare this image with the fanciful image of Tycho Brahe at work in his observatory (page 525).
¦ What metaphors and allegorical imagery did scientists use during this period to characterize the significance of their work?
“Knowledge is power.” The phrase is Bacon’s and captures the changing perspective of the seventeenth century and its new confidence in the potential of human thinking. Bacon trained as a lawyer, served in Parliament and, briefly, as lord chancellor to James I of England. His abiding concern was with the assumptions, methods, and practices that he believed should guide natural philosophers and the progress of knowledge. The authority of the ancients should not constrain the ambition of modern thinkers. Deferring to accepted doctrines could block innovation or obstruct understanding. “There is but one course left. . . to try the whole thing anew upon a better plan, and to commence a total reconstruction of sciences, arts, and all human knowledge, raised upon the proper foundations.” To pursue knowledge did not mean to think abstractly and leap to conclusions; it meant observing, experimenting, confirming ideas, or demonstrating points. If thinkers will be “content to begin with doubts,” Bacon wrote, “they shall end with certainties.” We thus associate Bacon with the gradual separation of scientific investigation from philosophical argument.
Bacon advocated an inductive approach to knowledge: amassing evidence from specific observations to draw general conclusions. In Bacon’s view, many philosophical errors arose from beginning with assumed first principles. The traditional view of the cosmos, for instance, rested on the principles of a prime mover and the perfection of circular motion for planets and stars. The inductive method required accumulating data (as Tycho had done, for example) and then, after careful review and experiment, drawing appropriate conclusions about the motions of heavenly bodies. Bacon argued that scientific knowledge was best tested through the cooperative efforts of researchers performing experiments that could be repeated and verified. The knowledge thus gained would be predictable and useful to philosophers and artisans alike, contributing to a wide range of endeavors from astronomy to shipbuilding.
Bacon’s vision of science and progress is vividly illustrated by two images. The first, more familiar, is the title page of Bacon’s Novum Organum (1620) with its bold ships sailing out beyond the Straits of Gibraltar, formerly the limits of the West, into the open sea, in pursuit of unknown but
FROM RENE DESCARTES, L'HOMME (1729; ORIGINALLY PUBLISHED AS DEHOMINI, 1662). Descartes's interest in the body as a mechanism led him to suppose that physics and mathematics could be used to understand all aspects of human physiology, and his work had an important influence on subsequent generations of medical researchers. In this illustration, Descartes depicts the optical properties of the human eye. ¦ How might such a mechanistic approach to human perception have been received by proponents of Baconian science, who depended so much on the reliability of human observations?
World History
