Chapter 1
Introduction
Avoiding Myths and Muddles
Galileo’s Legacy
In 1633, at the conclusion of one of history’s most famous trials, the Roman Inquisition found Galileo Galilei guilty of “vehement suspicion of heresy”; this was a specific category of religious crime intermediate in seriousness between formal heresy and mild suspicion of heresy. He had committed this alleged crime by defending the idea that the Earth is a planet rotating daily around its own axis and revolving yearly around the Sun; his argument was found in a book published the previous year and entitled Dialogue on the Two Chief World Systems, Ptolemaic and Copernican. The problem stemmed chiefly from the fact that Galileo was implicitly denying the Catholic Church’s beliefs that the Earth’s motion contradicted Scripture and Scripture was a scientific authority.
Thus, Galileo became the protagonist of a cause célèbre that continues to our own day. For example, in the eighteenth century, Voltaire opined that the tragedy would bring “eternal disgrace” to the Catholic Church; and in the twentieth century, Arthur Koestler labeled it “the greatest scandal in Christendom.”1
However, there is also irony in this tragedy. For, as we shall see later, eventually the Church came to recognize that Galileo was right not only about the Earth’s motion, but also about the limited authority of Scripture. This recognition came in 1893 when Pope Leo XIII issued an encyclical entitled Providentissimus Deus, propounding the Galilean principle that Scripture is not a scientific authority, but only one on questions of faith and morals. Moreover, another acknowledgment came in the period 1979–92, when Pope Saint John Paul II undertook a highly publicized and highly controversial “rehabilitation” of Galileo. John Paul made it clear and explicit that Galileo had been theologically right about biblical hermeneutics, as against his ecclesiastical opponents; moreover, the pope credited Galileo with having preached, practiced, and embodied the very important principle that religion and science are really in harmony, and not incompatible. In short, the world’s oldest religious institution, which continues to be one of the world’s great religions, has found ways and reasons to try to appropriate Galileo’s legacy with regard to two basic principles, involving the limited authority of Scripture and the harmonious relationship between science and religion.
It is not surprising that the Catholic Church would try to appropriate Galileo’s legacy. In fact, independently of his epoch-making role in the history and philosophy of religion, his legacy has a second main aspect: Galileo was one of the founders of modern science. That is, science as we know it today emerged in the sixteenth and seventeenth centuries thanks to the discoveries, inventions, ideas, and activities of a group of people like Galileo that also included Nicolaus Copernicus, Johannes Kepler, René Descartes, Christiaan Huygens, and Isaac Newton. Frequently, Galileo is singled out as the most pivotal of these founders and called the Father of Modern Science. Although many people have repeated or elaborated such a characterization, it is significant that it originates in the judgment of practicing scientists themselves, such as Albert Einstein and Stephen Hawking.2 Galileo’s most important contributions involved physics, astronomy, and scientific method.
In physics, Galileo pioneered the experimental investigation of motion. He also formulated, clarified, and systematized many of the basic concepts and principles needed for the theoretical analysis of motion, such as an approximation to the law of inertia, a formulation of the relativity of motion, and the composition of motion into distinct components. And he discovered the laws of falling bodies, including free fall, descent on inclined planes, pendulums, and projectiles.
In astronomy, Galileo introduced the telescope as an instrument for systematic observation. He made a number of crucial observational discoveries, such as mountains of the Moon, satellites of Jupiter, phases of Venus, and sunspots. And he understood the cosmological significance of these observational facts and gave essentially correct interpretations of many of them; that is, he provided a robust confirmation of the theory that the Earth moves, daily around its own axis and yearly around the Sun.
With regard to scientific method, Galileo pioneered several important practices. For example, he was a leader in the use of artificial instruments (like the telescope) to learn new facts about the world; this is to be contrasted to the use of instruments like the compass for practical purposes. Moreover, he pioneered the active intervention into and exploratory manipulation of physical phenomena in order to gain access to aspects of nature that are not detectable without such experimentation; this is the essence of the experimental method, as distinct from a merely observational approach. He also contributed to the establishment and extension of other more traditional, but little used, methodological practices, such as the use of a quantitative and mathematical approach in the study of motion. He contributed to the explicit formulation and clarification of important methodological principles, such as the setting aside of biblical assertions and religious authority in scientific inquiry. And he was also an inventor, making significant contributions to the devising and improvement of such instruments as the telescope, microscope, thermometer, and pendulum clock.
Finally, there is a third aspect to Galileo’s legacy. In fact, the historical circumstances of his time and his own personal inclinations made him into a kind of philosopher. Of course, he was not a systematic metaphysician who speculated about the eternal problems of being and nothingness. Instead he was a concrete-oriented and practical-oriented critical thinker who not only was engaged in a quest for knowledge of nature, but also reflected on questions about the nature of knowledge. In the eloquent words of Owen Gingerich, for Galileo “what was at issue was both the truth of nature and the nature of truth.”3 Now, let us define epistemology as the branch of philosophy that studies the nature of knowledge in general, and scientific knowledge in particular, including the principles and procedures that are useful in the acquisition of knowledge; if one focuses on just the latter principles and procedures, that defines the branch of epistemology called methodology. In this regard, Galileo was like the ancient Greek philosopher Socrates, their main difference being that Socrates reflected on moral or ethical questions of good and evil and the meaning of life. Thus, just as many regard Socrates as the Father of Western Philosophy, we may regard Galileo as the Socrates of methodology and epistemology.
That is, as already hinted at and as we shall see in more detail later, Galileo’s contributions to scientific knowledge were so radical that he constantly had to discuss with his opponents (scientific as well as ecclesiastic) not only what were the observational facts and what was their best theoretical interpretation, but also what were the proper rules for establishing the facts and for interpreting them. With scientific opponents he had to discuss questions such as whether artificial instruments like the telescope have a legitimate role in learning new truths about reality; whether scientific authorities, such as Aristotle (384–322 bc), should be relied upon to the exclusion of one’s own independent judgment; whether mathematics has an important, and perhaps essential, role to play in the study of natural phenomena; and so on. With ecclesiastic opponents, Galileo had to discuss whether Scripture should be treated as a source of scientific information about physical reality; whether scientific theories that contradict the literal meaning of Scripture should be summarily rejected or treated as hypotheses; whether hypotheses are potentially true descriptions of reality or merely convenient instruments of calculation and prediction; and so on.
In short, Galileo’s legacy clearly has a three-fold character, relating to science, religion, and philosophy. These three things are such major and crucial cultural elements, and their interaction has such significant cultural ramifications, that we may also speak more generally of his cultural legacy.
In this book, all aspects of Galileo’s cultural legacy are discussed by focusing on his trial by the Inquisition, stressing its intellectual developments and issues, and elaborating, in turn, its background, proceedings, aftermath, and significance. However, before articulating the background, it is important to have a methodological discussion outlining the multifaceted and balanced approach that is necessary to avoid common pitfalls. This approach requires a mastery of a number of distinctions, which, however, must not be turned into separations. It also requires an awareness of the non-intellectual factors, which cannot be totally neglected, even as one stresses intellectual aspects. Finally, this approach requires an awareness of such pedestrian things as dates, places, and names, and so a rudimentary sketch of Galileo’s life will be provided presently; such a biographical overview can also serve as a synthetic preview of this book’s chapters. To these three topics, I now turn.
Biographical Highlights
Galileo was born in Pisa in 1564 (Figure 1). At that time, the northern Italian city of Pisa was part of an independent state known as the Grand Duchy of Tuscany, which had Florence as its capital, and which was ruled by a grand duke of the famous House of the Medici. Pisa already had the claim to fame which it continues to have today: it was the site of a massive and monumental tower that had been leaning without falling ever since it was built in the thirteenth century. Thus, some myth makers have invented the legend that at some point Galileo performed experiments by dropping two cannon balls of different weights from the top of the tower, to test whether they reached the ground at the same time. Similarly, the year of Galileo’s birth happened to be the same as that of Michelangelo’s death, and this coincidence has led other myth makers to speak of a transmigration of a specially gifted soul from Michelangelo to Galileo. However, this particular fable overlooks the possibility that such a talented soul might have migrated to Shakespeare, who was also born in 1564.
Figure 1. Portrait of Galileo, published in his Sunspots (1613) and Assayer (1623)
Be that as it may, Galileo’s father, Vincenzo, was a musician, composer, and musicologist. Vincenzo was highly skillful at playing the lute, and a prolific writer and arranger of songs, but he was and remains best known for his revolutionary theories of music. In this field of musicology, his most relevant accomplishment was to preach and practice the need to test experimentally the empirical accuracy of rules of harmony. His many experiments dealt with how the audible and melodious sound produced by plucking a string changed as a result of various changes in the properties of the string; that is, changes in its length, tension, weight, material, etc. Such experimentation had not been done or updated in any sustained manner for two thousand years, since the ancient Greeks.
Vincenzo’s innovation is important because there can be no doubt that it was from his father that Galileo learned to practice and to appreciate the experimental method. However, Galileo also had his own original and revolutionary idea—utilizing experimentation in the study of falling bodies. Thus, Galileo’s own experiments dealt with how the speed of a falling body changed as a result of various changes in the parameters of the motion; that is, changes in height, time, weight, substance, impediments, etc.
In 1581, Galileo enrolled at the University of Pisa to study medicine, but soon switched to mathematics, which he also studied privately outside the university. After four years, he left the university without a degree and began to do private teaching and independent research. In 1589, he obtained a position as professor of mathematics at the University of Pisa, and then from 1592 to 1610 at the University of Padua.
At that time, Padua was part of the Republic of Venice, which was an independent state that included some territory in north-eastern Italy, some parts of the eastern coast of the Adriatic Sea, and some islands in the south-eastern Mediterranean Sea. The republic was then at the height of its power, despite continuing skirmishes and conflicts with the Ottoman Empire. In fact, Venice had led the European coalition that defeated the Ottoman Turks in the great naval battle of Lepanto in 1571. Thus, the city of Venice was at that time a world center of commerce and wealth, and of arts and culture.
This is important because the University of Padua was a state institution, and so for 18 years Galileo was a Venetian state employee. Moreover, Padua was located only 26 miles away from the city of Venice, and so during those 18 years Galileo often went there for business, entertainment, socializing, etc. Thus, it is not surprising that from a personal point of view those years were one of the happiest periods of his life. Still, he missed his native Tuscany and always regarded himself as a Tuscan citizen; he never quite accepted life as a Venetian, and did all he could to acquire a position in his native region.
Professionally speaking, during this Paduan period, Galileo was researching primarily the nature of motion. He was critical of the physics of Aristotle, and favorably inclined toward the statics and mathematics of another ancient Greek, Archimedes of Syracuse (287–212 bc). Galileo made great progress in this project, and it was then that he made most of his contributions and discoveries in physics. However, he did not publish any of these results during this earlier period.
Moreover, Galileo was acquainted with the theory of a moving Earth advanced by Nicolaus Copernicus (1473–1543) in his book On the Revolutions of the Heavenly Spheres (1543) (Figure 2). He was appreciative of the fact that Copernicus had advanced a novel argument. Galileo had also intuited that the Earth’s motion was more consistent in general with the new physics he was then developing than was the Earth standing still at the center of the universe; in particular, he had been attracted to Copernicanism because he felt that the Earth’s motion could best explain why the tides occur. However, he was acutely aware of the considerable evidence against Copernicanism, especially that stemming from astronomical observation; for example, the failure to detect annual changes in the fixed stars, to see phases for the planet Venus, and to discern similarities between the Earth and the heavenly bodies. Thus, Galileo judged that the anti-Copernican arguments far outweighed the pro-Copernican ones.
Figure 2. Nicolaus Copernicus (1473–1543)
However, his telescopic discoveries led Galileo to a major re-assessment of Copernicanism. In 1609, he perfected the telescope to such an extent as to make it an astronomically useful instrument that could not be duplicated by others for some time. By its means he made several startling discoveries which he immediately published in The Sidereal Messenger (1610): mountains on the Moon, satellites around the planet Jupiter, stellar composition of the Milky Way and nebulas, and countless stars never seen before. As a result, he became a celebrity, resigned his professorship at Padua, was appointed Philosopher and Chief Mathematician to the grand duke of Tuscany, and moved to Florence the same year. Soon thereafter, he also discovered the phases of Venus and sunspots; on the latter, he published the History and Demonstrations Concerning Sunspots (1613). Although he realized that these discoveries did not conclusively establish the Copernican theory, he had no doubt that they confirmed it.
This realization also encouraged Galileo to be more critical of the theological objections to Copernicanism, although he was careful and prudent because he knew that this aspect of the problem was potentially dangerous and explosive. His telescopic discoveries and their Copernican interpretation had immediately been criticized on scriptural grounds. At first, he ignored such attacks. But eventually he felt he could not remain silent, and decided to refute the biblical argument against Copernicus. To avoid scandalous publicity, he wrote his criticism in the form of long private letters, in December 1613 to his disciple Benedetto Castelli, and in spring 1615 to the grand duchess dowager Christina.
Galileo’s letters circulated widely and the conservatives got even more upset. Thus, in February 1615, a Dominican friar filed a written complaint against Galileo with the Inquisition in Rome. An investigation was launched that lasted about a year. As part of this inquiry, a committee of Inquisition consultants reported that the key Copernican theses about the Earth’s motion were absurd and false in natural philosophy and heretical in theology. The Inquisition also interrogated other witnesses.
However, Galileo himself was not summoned or interrogated, partly because the key witnesses exonerated him and partly because Galileo’s letters had not been published, whereas his published writings contained neither a categorical assertion of Copernicanism nor a denial of the scientific authority of Scripture. Nor did the Inquisition issue a formal condemnation of Copernicanism as a heresy. Instead two milder consequences followed.
In February 1616, Galileo himself was given a private warning by Cardinal-Inquisitor Robert Bellarmine forbidding him to hold or defend the truth of the Earth’s motion; Galileo agreed to comply. And in March, there was a decree by the Congregation of the Index, the less authoritative department in charge of book censorship: without mentioning Galileo at all, it declared the Copernican doctrine false and contrary to Scripture, and it temporarily banned Copernicus’s 1543 book.
For the next several years, Galileo kept quiet about the forbidden topic, until 1623 when Florentine Cardinal Maffeo Barberini became Pope Urban VIII. Barberini was an old admirer and patron, and so Galileo felt freer and decided to write the book on the system of the world conceived earlier, adapting its form to the new restrictions. Galileo wrote the book in the form of a dialogue among three characters engaged in a critical discussion of the cosmological, astronomical, physical, and philosophical arguments, but avoiding the biblical or theological ones.
This Dialogue on the Two Chief World Systems, Ptolemaic and Copernican was published in 1632. Its key thesis is that the arguments favoring the Earth’s motion were stronger than those favoring the Earth’s rest, and in that sense Copernicanism was more probable than the traditional view. Galileo managed to incorporate into the discussion the new telescopic discoveries, his conclusions about the physics of moving bodies, frequent methodological reflections, and an explanation of the tides in terms of the Earth’s motion (the so-called tidal argument).
However, his enemies raised several complaints. A key charge was that the book defended the truth of the Earth’s motion, which he had been forbidden to do. Thus, he was summoned to Rome to stand trial, which began in April 1633. At the first interrogation, Galileo denied that his book defended the Earth’s motion, claiming instead that it was a critical examination of the arguments on both sides. There followed an out-of-court plea-bargaining meeting, during which he was persuaded to plead guilty to this charge in exchange for leniency. So, at the next deposition, he admitted having defended the Earth’s motion, but insisted that this was unintentional. The trial concluded with a sentence that found him guilty of “vehement suspicion of heresy,” an intermediate category of religious crime; the Dialogue was banned; and he was to be under indefinite house arrest.
One of the ironic results of this condemnation was that, after the trial, to keep his sanity, Galileo went back to his earlier research on motion. Thus, he organized his old notes, and five years later published his most important contribution to physics, the Two New Sciences (1638). Without the tragedy of the trial, he might have never done it. He died in Arcetri (near Florence) in 1642, surrounded by family and disciples.
Galileo’s condemnation started a controversy that shows no signs of abating. He became a cultural icon. His tragedy acquired paradigmatic significance for the perennial and universal problem of the relationship between science and religion. And his manner of thinking and search for truth became a model of rationality, scientific method, and critical thinking, to be considered by anyone engaged in such a search.
A New Approach to Galileo’s Trial
The most common view about the trial of Galileo is that it epitomizes the conflict between enlightened science and obscurantist religion. One version of this view may be gathered from an inscription on a public monument in Rome near Villa Medici. This is the palace where Galileo resided on some of his visits to Rome, and where he was held under house arrest for about a week after the 1633 sentence. The inscription reads: “The palace next to this spot, / which belonged formerly to the Medici, / was a prison for Galileo Galilei, / guilty of having seen / the earth turn around the sun.”
The historical and cultural importance of this minor tourist attraction is that it expresses some of the most common myths widely held about the trial of Galileo: that, with his telescope, he “saw” the Earth’s motion (an observation still impossible to make even in the twenty-first century); that he was “imprisoned” by the Inquisition (whereas he was held under house arrest); and that his crime was to have discovered the truth. Now, since to condemn someone for this reason can result only from ignorance, prejudice, and narrow-mindedness, we also have here a formulation of the myth that alleges the incompatibility between science and religion.
The incompatibility thesis is very widespread. For example, various formulations of it have been advanced by such scientific, philosophical, and cultural icons as Voltaire, Bertrand Russell, Albert Einstein, and Karl Popper. However, I believe that such a thesis is erroneous, misleading, and simplistic, and will return to consider it in depth in Chapter 9.
For the moment, one main reason for identifying this first anti-clerical myth about the trial is that it may be usefully contrasted to a second myth at the opposite extreme. It seems that some found it appropriate to fight an objectionable myth by constructing another.
The opposite anti-Galilean myth maintains that Galileo deserved condemnation because he violated not only various ecclesiastical norms, but also various rules of scientific methodology and logical reasoning; he is thus portrayed as a master of cunning and knavery, and it is difficult to find a misdeed of which the proponents of this myth have not accused him. The history of this myth too has its own fascination; it too includes illustrious names, such as French physicist, philosopher, and historian Pierre Duhem, German playwright Bertolt Brecht, Hungarian intellectual Arthur Koestler, and Austrian-American philosopher Paul Feyerabend; and this myth and its underlying thesis will also be discussed in more detail later (Chapters 8 and 9).
These two opposite myths are useful as reference points in order to orient oneself in the study of the controversy, since it is impossible to evaluate the trial adequately unless one admits that both of these accounts are mythological and thus rejects both. However, avoiding them is easier said than done. For example, one cannot simply follow a mechanical approach of mediating a compromise by dividing in half the difference that separates them. A helpful way of proceeding is to read the relevant texts and documents with care and with an awareness of a number of crucial conceptual distinctions.
One of the most important of these distinctions is that the trial of Galileo involved both questions about the truth of nature and the nature of truth, to use Owen Gingerich’s (1982) eloquent expression quoted earlier. That is, the controversy was at least two-sided: it involved partly scientific issues about physical facts, natural phenomena, and astronomical and cosmological matters; and it also involved methodological and epistemological questions about what truth is and the proper way to search for it, and about what knowledge is and how to acquire it.
The overarching scientific issue was whether the Earth stands still at the center of the universe, with all heavenly bodies revolving around it, or whether the Earth is itself a heavenly body that rotates on its axis every day and revolves around the Sun once a year. There were several distinct but interrelated questions here. One was whether the whole universe revolves daily from east to west around a motionless Earth, or the Earth alone rotates daily on its axis in the opposite direction (west to east); this was the problem of whether the so-called diurnal motion belongs to the Earth or to the rest of the universe. Another question was whether the Sun revolves yearly from west to east around the Earth, or the Earth revolves in the same direction around the Sun; this was the issue of whether the so-called annual motion belongs to the Sun or to the Earth. Another aspect of the controversy was whether the center of the universe, or at least the center of the revolutions of the planets, is the Earth or the Sun. And there was also the problem of whether the universe is divided into two very different regions, containing bodies made of different elements, having different properties, and moving and behaving in different ways: the terrestrial or sublunary part where the earth, including water and air, are located; and the celestial, heavenly, or superlunary region, beginning at the Moon and extending beyond to include the Sun, planets, and fixed stars.
The traditional view may be labeled geostatic, insofar as it claims the Earth to be motionless; or geocentric, insofar as it locates the Earth at the center of the universe; or Ptolemaic, insofar as in the second century ad the Greek astronomer Claudius Ptolemy (about ad 100–78) had elaborated it in sufficient detail to make it a workable theoretical system; or Aristotelian, insofar as it corresponded to the worldview advanced in the fourth century bc by the Greek philosopher Aristotle, whose ideas in a wide variety of fields had become predominant in the sixteenth century. The other view may be called either geokinetic, insofar as it holds the Earth to be in motion; or heliocentric, insofar as it places the Sun at the center; or Copernican, named after Nicolaus Copernicus, who in the first half of the sixteenth century elaborated its details into a workable theoretical system; or Pythagorean, named after the ancient Greek pre-Socratic Pythagoras, who was one of the earliest thinkers (sixth century bc) to advance the idea in a general way. We may thus say that the scientific issue was essentially whether the geostatic or the geokinetic theory is true, or at least whether one or the other is more likely to be true.
The epistemological and methodological issues were several. There was the question of whether physical truth has to be directly observable, or whether any significant phenomenon (e.g., the Earth’s motion) can be true even though our senses cannot detect it directly, but can detect only its effects; remember that even today the Earth’s motion cannot be seen directly by an observer on Earth. Then there was the question of whether artificial instruments like the telescope have any legitimate role in the search for truth, or whether the proper way to proceed is to use only the natural senses; in fact, the telescope was the first artificial instrument ever used to learn novel scientific or philosophical truths about the world. A third issue of this sort involved the question of the role of the Bible in scientific inquiry, whether its assertions about natural phenomena have any authority, or whether the search for truth about nature ought to be conducted completely independently of the claims contained in the Bible; this was not only a methodological or epistemological issue, but also a theological or hermeneutical one, and it was the paramount issue in the trial, since it was widely believed that the new geokinetic theory contradicted the Bible. Fourth, there was the question of the nature of hypotheses and their role in the search for truth: whether they are merely instruments for mathematical calculation and observational prediction that can be only more or less convenient but neither true nor false, or whether they are assumptions about physical reality that are more or less probable and potentially true or false but not yet known with certainty; here, this problem stemmed from the fact that even the anti-Copernicans admitted that one could explain the motion of the heavenly bodies by means of the hypothesis of the Earth’s motion, but they took this as a sign of its instrumental convenience and not of its truth, potential truth, or probable truth. Let us call these four central issues, respectively, the problems of the observability of truth; the legitimacy of artificial instruments; the scientific authority of the Bible; and the role of hypotheses (or the problem of instrumentalism vs. realism).
For the second needed conceptual clarification, one must distinguish between factual correctness and rational correctness; that is, between being right about the truth of the matter and having the right reasons for believing the truth. Suppose we begin by asking who was right about the scientific issue. It is obvious that Galileo was right and his opponents were wrong, since he preferred the geokinetic to the geostatic view, and today we know for a fact that the Earth does move and is not standing still at the center of the universe. However, it is equally clear that his being right about this fact does not necessarily mean that his motivating reasons were correct, since it is conceivable that although he might have chanced to hit upon the truth, his supporting arguments may have been unsatisfactory. Hence, the evaluation of his arguments is a separate issue.
I am not saying that the various proponents of the anti-Galilean accounts are right when they try to show that his arguments left much to be desired, ranging from inconclusive to weak to fallacious to sophistical. In fact, in my opinion, this evaluation is untenable.4 Rather, I am saying that Galileo’s critics have raised a distinct and important issue about Galileo’s trial—namely, whether, or to what extent, his reasoning was correct.
The next distinction that must be appreciated is also easy when stated in general terms but extremely difficult to apply in practice. It is that essential correctness must not be equated with either total correctness or perfect conclusiveness. Applied to our case, this means that even if Galileo’s arguments were essentially correct, as I would hold, the possibility must be allowed that the reasoning of his opponents was not worthless, nor irrelevant, nor completely unsound.5 This point is a consequence of the fact that we are dealing with arguments which logicians would label non-apodictic; that is, they are not completely conclusive, but rather susceptible of degrees of rational correctness. Thus, it is entirely conceivable that there should sometimes be good arguments in support of opposite sides, as well as that the arguments for one side should be better than those for the opposite, without the latter being worthless. I believe this is the case for the trial of Galileo, though it is something the anti-clerical critics do not seem to be able to understand. The proper antidote here is the study of the details of the relevant arguments.
To appreciate the next distinction, let us ask whether Galileo or the Church was right in regard to the epistemological and methodological aspect of the controversy. Since such issues are normally more controversial than scientific ones, this is an area which some like to exploit by trying to argue that the Church’s epistemological and philosophical insight was superior to Galileo’s. The argument is usually made in the context of a frank and explicit admission that Galileo was unquestionably right on the scientific issue. Thus, these anti-Galilean critics often boast to be displaying even-handedness and balanced judgment by contending that on the one hand Galileo was right from a scientific or factual point of view, but that on the other hand the Church was right from an epistemological or philosophical point of view.
However, such interpretations can be criticized for their exaggeration, one-sidedness, and superficiality in the analysis of the epistemological component of the affair.6 For example, I have already mentioned that there were at least four epistemological issues in the affair, and I am very doubtful that they can all be reduced to one. Moreover, it cannot be denied that Galileo turned out to be right on at least some of the epistemological issues—for example, those pertaining to the legitimacy of artificial instruments and to the Bible lacking scientific authority. On this last point, recall that, as mentioned earlier, it is now more than one hundred years since the Catholic Church officially adopted the Galilean principle that the Bible is an authority only in matters of faith and morals, and not in questions of natural science, with Pope Leo XIII’s encyclical on the subject. Furthermore, it seems to me that with the epistemological issues too one can apply the distinction between factual and rational correctness, and thus introduce the question of the rationale underlying the two conflicting positions. That is, we can examine their respective arguments and try to determine which were the better ones, although this is more difficult here than in the case of the scientific arguments.
The main point of this last series of considerations is not to decide the initial question with which they began, but rather to underscore the multiplicity of the epistemological issues in the Galileo affair, and to suggest avoiding any one-sided focus on a single one.
Finally, one must bear in mind that this episode was not merely an intellectual affair. Besides the scientific, astronomical, physical, cosmological, epistemological, methodological, theological, hermeneutical, and philosophical issues, and besides the arguments pro and con, there were legal, political, social, economic, personal, and psychological factors involved. To be sure, it would be a mistake to concentrate on these external issues, or even to devote to them equal attention in comparison with the intellectual issues, for the latter constitute the heart of the episode, and so they must have priority. Nevertheless, it would be equally a mistake to neglect the external, or non-intellectual, factors altogether. To them I now turn.
Non-intellectual Factors
Beginning with personal or psychological factors, it is easy to see that Galileo had a penchant for controversy, was a master of wit and sarcasm, and wrote with unsurpassed eloquence. Interacting with each other and with his scientific and philosophical virtues, these qualities resulted in his making many enemies and getting involved in many other bitter disputes besides the main one that concerns us here. Typically, these disputes involved questions of priority of invention or discovery, and fundamental disagreements about the occurrence and interpretation of various natural phenomena. Major controversies included a successful lawsuit against another scholar for plagiarism in regard to Galileo’s invention of a calculating device and its accompanying instructions (1606–7); a dispute with his philosophy colleagues at the University of Padua, where he taught mathematics, about the exact location of the novas that became visible in the heavens in October 1604; a dispute with other philosophers in Florence in 1612 about the explanation of why bodies float in water; a dispute with a German Jesuit astronomer named Christoph Scheiner (1573–1650) about priority in the discovery of sunspots and about their proper interpretation, beginning in 1612 and lasting to the end of their lives; and a dispute with an Italian Jesuit astronomer named Orazio Grassi (1590–1654) about the nature of comets, sparked by the appearance of some of these phenomena in 1618. Given what all this indicates about Galileo’s personality, one may wonder how he managed to acquire and keep the many friends and admirers he did.
Moving on to social and economic factors, it should be noted that Galileo was not wealthy. He had to earn his living, first as a university professor, and then under the patronage of the grand duke of Tuscany. During his university career, from 1589 to 1610, his economic condition was always precarious. His university salary was very modest, and this was especially so given that he taught mathematics and thus received only a fraction of the remuneration given to a professor of philosophy. This only compounded other unlucky family circumstances, such as having to provide dowries for his sisters. Galileo was forced to supplement his salary by giving private lessons, by taking on boarders at his house, and by working on and managing a profitable workshop that built various devices, some of his own invention. These financial difficulties eased in the second half of his life when he attained the position of “philosopher and chief mathematician” to the grand duke of Tuscany. However, in this position he was constantly facing a different problem, stemming from the nature of patronage and his relationship to his patron:7 since the fame and accomplishments of an artist, philosopher, or scientist were meant to reflect on the magnificence of the patron, Galileo was in constant need to prove himself scientifically and philosophically, either by surpassing the original accomplishments that had earned him the position or by giving new evidence for that original worth.
The politics of Galileo’s trial has to be understood in the context of the Catholic Counter-Reformation. Martin Luther had started the Protestant Reformation in 1517, and the Catholic Church had convened the Council of Trent in 1545–63. So Galileo’s troubles developed and climaxed during a time of violent struggle between Catholics and Protestants. Since he was a Catholic living in a Catholic country, it was also a period when the decisions of that council were being taken seriously and implemented and thus affected him directly. Aside from the question of papal authority, one main issue dividing the two camps was the interpretation of the Bible—both how specific passages were to be interpreted and who was entitled to do the interpreting. The Protestants were inclined toward relatively novel and individualistic or pluralistic interpretations, whereas the Catholics were committed to relatively traditional interpretations by the appropriate authorities.
More specifically, the climax of the trial in 1632–3 took place during the so-called Thirty Years War (1618–48) between Catholics and Protestants.8 At that particular juncture, Pope Urban VIII, who had earlier been an admirer and supporter of Galileo, was in an especially vulnerable position; thus, not only could he not continue to protect Galileo, but he used Galileo as a scapegoat to reassert, exhibit, and test his authority and power. The problem stemmed from the fact that in 1632 the Catholic side led by the King of Spain and the Bohemian Holy Roman Emperor was disastrously losing the war to the Protestant side led by the King of Sweden, Gustavus Adolphus. Religion was not the only issue in the war, which was being fought also over dynastic rights and territorial disputes. In fact, ever since his election in 1623, the pope’s policy had been motivated primarily by political considerations, such as his wish to limit and balance the power of the Hapsburg dynasty which ruled Spain and the Holy Roman Empire. It had also been motivated by personal interest—that is, cooperation with the French, whose support had been instrumental in his election, and who for nationalistic reasons also opposed the Hapsburg hegemony. In the wake of Gustavus Adolphus’s spectacular victories, the Spanish and Imperial ambassadors were accusing Urban of having favored and helped the Protestant cause. They mentioned such things as his failure to send the kind of military and financial support which popes had usually provided on such occasions, and his refusal to declare the war a holy war. There were even suspicions of a more direct understanding with the Protestants. Thus, the pope’s own religious credentials were being questioned, and there were rumors of convening a council to depose him.
Then there was what may be called the Tuscan factor, which had at least two political aspects. One was that the Grand Duchy of Tuscany, whose ruler Galileo served, was closely allied with Spain, and so the pope’s intransigence with him was in part a way of getting back at Spain. The other was related to the fact that many of the leading protagonists in Galileo’s trial were Tuscan: for example, Cardinal Robert Bellarmine, the key figure in the earlier phase of the proceedings, and Pope Urban VIII (of the House of Barberini), the moving force of the later proceedings. Thus the entire episode has some of the flavor of a family squabble.
Finally, another political element involved the internal power struggle within the Church, on the part of various religious orders, primarily the Jesuits and the Dominicans, but to some extent also the Capuchins. In the earlier phase of the trial, in 1615–16, Galileo seems to have been attacked by Dominicans and defended by Jesuits, whereas in the later phase, in 1632–3, it seems that the two religious orders had exchanged roles. It is important to appreciate the significance of such internal dissent: the Church was far from being a monolithic entity.
Just as the political background of the affair involved primarily matters of religious politics, so the legal background involved essentially questions of ecclesiastical, or “canon,” law.9 In Catholic countries, the activities of intellectuals like Galileo were subject to the jurisdiction of the Congregation of the Index and the Congregation of the Holy Office, or Inquisition. In the administration of the Catholic Church, a “congregation” is a committee of cardinals charged with some department of Church business.
The Congregation of the Index was instituted by Pope Pius V in 1571 with the purpose of book censorship. One of its main responsibilities was the compilation of a list of forbidden books (called Index librorum prohibitorum). This Congregation was abolished by Pope Benedict XV in 1917, and thereafter book censorship was handled once again by the Congregation of the Holy Office, which had been in charge of the matter before 1571.
The Congregation of the Holy Office, in turn, had been instituted in 1542 by Pope Paul III with the purpose of defending and upholding Catholic faith and morals. One of its specific duties was to take over the suppression of heresies and heretics which had been handled by the Medieval Inquisition; hence, from that time onward, the “Holy Office” and the “Inquisition” became practically synonymous. In 1965, at the Second Vatican Council, its name was officially changed to Congregation for the Doctrine of the Faith.
At the time of Galileo, the Inquisition or Holy Office had a complex bureaucracy; the notion of heresy had been given something of a legal definition; and inquisitorial procedures had been more or less codified.
The Inquisition was the most important and authoritative congregation in the Church. This was reflected partly in the fact that it was the only congregation whose head (called “prefect”) was the pope himself. Moreover, its membership consisted of about ten cardinal-inquisitors, which made it the largest congregation. Furthermore, its powers were greater, in the sense that it was not only the supreme judicial tribunal adjudicating particular cases, but also a legislative body whose decisions could enact new laws or change previous ones. Although it usually followed past practice and precedent and various explicitly formulated rules, it was not bound by them.
The Inquisition’s bureaucracy was correspondingly numerous and complex. Like most other congregations, it had a secretary, whose position was usually filled by the most senior member of the committee, and whose task was to handle correspondence. However, unlike other congregations, it had a professional staff: the commissary, who played the role of an executive secretary; the assessor, who was the chief legal officer; the prosecutor; and the notary, who was in charge of record-keeping. Each of these had an assistant. Then there were the consultants, who subdivided into two groups: theologians and legal experts. Finally, the Inquisition had offices in all major cities, each headed by a “provincial” inquisitor.
Although the Inquisition dealt with other offenses such as witchcraft, it was primarily interested in two main categories of crimes: formal heresy and suspicion of heresy. The term suspicion in this context did not have the modern legal connotation pertaining to allegation and contrasting it to proof. One difference between formal heresy and suspicion of heresy was the seriousness of the offense. For example, a standard Inquisition manual of the time stated that “heretics are those who say, teach, preach, or write things against the Holy Scripture; against the articles of the Holy Faith; … against the decrees of the Sacred Councils and the determinations made by the Supreme Pontiffs; … those who reject the Holy Faith.”10 The same manual stated that
suspects of heresy are those who occasionally utter propositions that offend the listeners … those who keep, write, read, or give others to read books forbidden in the Index and in other particular Decrees; … those who receive the holy orders even though they have a wife, or who take another wife even though they are already married; … those who listen, even once, to sermons by heretics.11
Another difference between formal heresy and suspicion of heresy was whether the culprit, having confessed the incriminating facts, admitted having an evil intention.12 Furthermore, within the major category of suspicion of heresy, two main subcategories were distinguished:13 vehement suspicion of heresy and slight suspicion of heresy; their difference depended on the seriousness of the criminal act. Thus, in effect there were three main types of religious crimes, in descending order of seriousness: formal heresy, vehement suspicion of heresy, and slight suspicion of heresy.
When it came to procedure, there were two ways in which legal proceedings could begin: either by the initiative of an inquisitor, based on publicly available knowledge or publicly expressed opinion; or in response to a complaint filed by some third party, who was required to make a declaration of the purity of his motivation and to give a deposition. Then there were specific rules about the interrogation of defendants and witnesses; how injunctions and decrees were to be worded; how, when, and why interrogation by torture was to be used; and the various kinds of judicial sentences and defendant’s abjurations with which to conclude the proceedings.
To summarize, the cultural legacy of Galileo in science, religion, and philosophy can be effectively elaborated by focusing on his trial (its background, proceedings, aftermath, and significance) and by stressing the intellectual developments and issues. However, a balanced approach must be followed, by avoiding the two opposite extremes exemplified by the anti-Galilean and anti-clerical myths, and by not completely overlooking the non-intellectual factors. There is no easy way of doing this, but it is helpful to distinguish scientific from epistemological (or methodological) issues, factual correctness from rational correctness, essential correctness from total correctness, the several epistemological issues from each other, intellectual from external factors, and the several external factors (personal-psychological, social, economic, political, and legal) from each other. However, these distinct aspects are also interrelated, so the point is not to deny their interaction, but to make sure they are not confused or conflated with one another. With these methodological tips in mind, let us move on to look in detail at the background to the trial.