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Author Biography: Maurice A. Finocchiaro is Distinguished Professor of Philosophy at the University ofNevada, Las Vegas.
1.1. From prehistoric times until the middle of the sixteenth century, almost all thinkers believed that the earth stood still at the center of the universe and that all heavenly bodies revolved around it. By the end of the seventeenth century, most thinkers had come to believe that the earth is the third planet circling the sun once a year and spinning around its own axis once a day. Nowadays, after three more centuries of accumulating knowledge, this modern view is known to be true beyond any reasonable doubt. But the earlier view had been a very plausible belief; for two millennia the earth's motion had been inconceivable or untenable, and then for a century and a half, the discussion of the relative merits of the two views was the subject of heated debate. In fact, the transition was a slow, difficult, and controversial process. We may fix its beginning with the publication in 1543 of Nicolaus Copernicus's book On the Revolutions of the Heavenly Spheres and its completion with the publication in 1687 of Isaac Newton's Mathematical Principles of Natural Philosophy .
The discovery of the motion and noncentral location of the earth involved not only a key astronomical fact, but was interwoven with thediscovery of the most basic laws of nature, such as the laws of inertia, of force and acceleration, of action and reaction, and of universal gravitation. This discovery was also connected with the clarification of some key principles of scientific method. It represents, therefore, the most
significant breakthrough in the history of science; thus, the series of developments starting with Copernicus in 1543 and ending with Newton in 1687 may be labeled the Scientific Revolution.1
More generally, it would perhaps be no exaggeration to say that this transition represents the most important intellectual transformation in human history.2 One reason for this involves the worldwide repercussions of the Scientific Revolution itself; science seems to be the only cultural force which has managed to dominate human societies in all parts of the earth. Another reason stems from the interdisciplinary character of the transition from a geocentric to a geokinetic world view; the transformation involved not only many branches of science but also other disciplines and activities such as philosophy, theology, religion, art, literature, technology, industry, and commerce; indeed it changed mankind's self-image in general. We may thus also call this transition the Copernican Revolution, if we want a label which leaves open its broad ramifications outside science; this label also gives due credit to the one thinker whose contribution initiated the process.3
Galileo Galilei (1564–1642) was a key protagonist of these historical developments. In physics, he pioneered the experimental investigation of motion; he formulated, clarified, and systematized many of the basic concepts needed for the theoretical analysis of motion; and he discovered the laws of falling bodies. In astronomy, he introduced the telescope as an instrument for systematic observation; he made several crucial observational discoveries; and he understood the cosmological significance of these observational facts and gave essentially correct interpretations of many of them. Galileo was also an inventor, making significant contributions to the devising and improvement of such instruments as the telescope, microscope, thermometer, and pendulum clock. In regard to scientific method, he pioneered several important practices, such as the use of artificial instruments (like the telescope) to learn new facts about the world, and the active intervention into and exploratory manipulation of physical phenomena to gain access to aspects of nature which are not detectable without such experimentation; he also contributed to the establishment and extension of other more traditional methodological practices, such as the use of a quantitative approach in
For some valuable accounts centered around this theme, see H. F. Cohen (1994), Hall (1954), and Lindberg and Westman (1990).
This thesis is generally attributed to Butterfield (1949).
For a classic example of this type of general account, see Kuhn (1957).
the study of motion; and he contributed to the explicit formulation and clarification of important methodological principles, such as the disregard of biblical assertions and religious authority in scientific inquiry.4
Galileo's Dialogue on the Two Chief World Systems, Ptolemaic and Copernican (1632) is one of the most important texts of the Copernican or Scientific Revolution. It also constitutes his mature synthesis of astronomy, physics, and scientific methodology. From the viewpoint of the transition from geocentrism to Copernicanism, the book may be summarized by saying that it strengthened the geokinetic theory by means of theoretical considerations based on Galileo's new physics, observational evidence stemming from his telescopic discoveries, and concrete methodological analyses.
Galileo's Dialogue is also the book which triggered his trial by the Roman Catholic Inquisition in 1633, ending with his condemnation as a heretic and the banning of the book. The trial was the climax of a series of events that began in 1613 and included a related series of Inquisition proceedings in 1615–1616. This twenty-year sequence of developments is now known as the Galileo Affair, and so the book is also an important document in this tragic but instructive episode (of which more below).
Because the Galileo Affair involved a conflict between one of the founders of modern science and one of the world's great religious institutions, it has traditionally been taken as an example of the warfare between science and religion. Whether this is really so is one of the main issues in the controversy that has arisen about the interpretation and evaluation of the Galileo Affair. This issue cannot be resolved here, but two comments are in order. First, even a cursory reading of the relevant documents shows that many churchmen were on his side and many scientists were on the opposite side; thus, there was a split within both science and religion, along the lines of what may be called conservation and innovation; so the real conflict was between a conservative attitude and a progressive one. Second, many of the problems between Galileo and the Church stemmed from the fact that the Church was then not just a religious authority but also a political power and a social institution; thus, the episode illustrates the conflict or interaction between science and politics, between science and society, and between individual freedom and institutional authority.
For some good scholarly general accounts see Drake (1978; 1990) and Geymonat (1965); for some interesting popular general accounts see Reston (1994), Ronan (1974), and Seeger (1966).
These remarks highlight the historical significance of the Dialogue by way of its connection with the Scientific Revolution, Copernican Revolution, and Galileo Affair. These episodes have such a perennial interest and universal relevance that the book thereby acquires perennial and universal significance. So far this means only that it is worth reading by all educated persons and by every generation in order for them to acquire factual information, come to their own interpretation, formulate their own evaluation, and derive their own lessons. But its perennial and universal importance can be elaborated in more abstract ways that connect it to several general activities of the human mind.
1.2. First, Galileo wrote the book in vernacular Italian rather than in scholarly Latin. His main motive was that he wanted to appeal to a broad audience of educated nonexperts and to suggest that the issues raised were of general cultural significance. This intention does not mean that he was addressing the book only to such readers; rather he wrote it for a professional audience of scholars and specialists, as well as for a lay audience of educated, intelligent, studious, and curious persons. However, what deserves emphasis here is that the book has an explicitly universalist aim.
Moreover, Galileo wrote the book in the form of a dialogue among three speakers: Salviati, an expert who takes the Copernican side; Simplicio, a scholar who takes the geocentric viewpoint; and Sagredo, an intelligent, educated, and inquisitive layman who knows little about the topic but wants to listen to both sides and make up his mind as a result of the critical scrutiny of what they have to say. This feature is in part connected with the Galileo Affair and will be discussed again below. The point to stress here is that the dialogue form reinforces the book's universal appeal inasmuch as the speakers personify the abstract intellectual issues and make it easier for readers to relate to them. But the dialogue form is also directly connected with another important aspect of the book, to which we now turn.
The book's most striking feature is critical reasoning, taking this term to mean reasoning aimed at the analysis, evaluation, and/or self-reflective presentation of arguments.5 In fact, Galileo was writing before the
This definition has been inspired by Michael Scriven, although it does not represent a mere adoption of his exact definition, but rather a formulation of a concept that I needed to make sense of Galileo's book; cf. Scriven and Fisher (forthcoming). For example, it should be noted that here I am talking of critical reasoning , whereas Scriven is talking about critical thinking , which I take to be a broader concept and to include also what I call methodological reflection; for more details see the appendix (1.6, 1.8, 2.1, and 2.7).
new Copernican view was conclusively established, when the situation was fluid and controversial; thus, to form an intelligent opinion on the topic required more than mere observation, experiment, calculation, or deduction; it required reasoning, judgment, analysis, evaluation, and argumentation. So it is not surprising that he felt the most fruitful thing to do was to undertake a critical examination of the arguments on both sides of the controversy. His overall conclusion was clearly that the Copernican side was preferable to the geocentric side. But this means only that Copernicanism was more probable or more likely to be true than geocentrism; that is, that the pro-Copernican arguments were stronger than the anti-Copernican ones; or again, that the reasons for believing the earth to be in motion were better than those for believing it to stand still; or finally, that the evidence or support favoring the geokinetic idea outweighed the evidence or support favoring the geostatic one. Galileo's conclusion was not that Copernicanism was clearly true or certainly true or absolutely true or demonstrably true,6 nor was it that there were no reasons for believing the earth to stand still; nor was it that the geostatic arguments were worthless. The point is that the book's key thesis is one about the relative merits of the arguments on each side, that this thesis is substantiated and not merely asserted, and that the substantiation proceeds by the reasoned presentation, analysis, and evaluation of the arguments. In short, critical reasoning is a key part of both the book's content and the book's approach.
Despite the prevalence of critical reasoning, we should not be too one-sided about it; for the Dialogue is also full of methodological reflections. By methodological reflections I mean7 discussions meant to formulate, clarify, evaluate, and use general principles about the nature of truth or knowledge and about the proper procedure to follow in the search for truth and the quest for knowledge; by calling them reflections I mean to stress that they arise in the context of a particular investigation
This interpretation will be elaborated and defended later in the introduction (5) and the appendix (I).
This definition of methodological reflection, together with the earlier definition of critical reasoning, makes clear that the two are different; thus I will usually treat them as distinct activities. But for certain purposes it is useful to associate critical reasoning and methodological reflection under the single heading of critical thinking; while the two remain distinct, this association interrelates them; this is discussed in the appendix (1.8, 2.1, and 2.7). On the other hand, I will usually treat "methodological reflection" and "epistemological reflection" as interchangeable terms; and the same holds for "methodology" and "epistemology"; I will do so even though these two things are not completely identical and in some contexts a distinction is drawn between them; this is discussed in the appendix (2.1).
about what is physically true or what we know of physical reality, and so they function to help us understand better what we are doing and decide what we should be doing. That is, issues and principles about truth, method, and knowledge are constantly discussed in the book, not because Galileo intends or pretends to write an abstract treatise about the nature of these concepts, but because the specific scientific questions (about whether or not the earth is standing still at the center of the universe) are so basic that they raise questions about how one is proceeding and about the proper way to proceed. For example, there are discussions about the nature and proper role of authority, observation versus intellectual theorizing, the limitations of human understanding, independent-mindedness and open-mindedness, simplicity, probability, experiments, mathematics, artificial instruments, the Bible, divine purpose and human interest, and causal explanation.
The Dialogue is also a gold mine of rhetoric, but here one must be especially careful. In this context, I take rhetoric to mean8 the theory and practice of verbal communication, involving not only persuasive argumentation but also such forms and techniques as emotional expression, beautiful language, imaginative description, bare assertion, nuanced assertion, repetition, wit, satire, humor, and ridicule. The wealth and complexity of the book's rhetoric derive in part from its universalist aim, which implies that Galileo is addressing several audiences at once; they derive in part from its dialogue form, which means that there is a certain amount of drama unfolding before the reader; the book's rhetoric also stems from the controversial character of the scientific and methodological issues discussed, which means that we are witnessing a polemical discussion; it also stems from the context of Galileo's struggle with the Church, which means that in writing the book he was taking considerable risk and could not always say what he meant or mean what he said; the rhetoric originates to some extent from the fact that the practice of science at that time was socially and financially dependent for the most part on the patronage of princes, which means generally that Galileo's career was partly that of a courtier and specifically that his book represented an action in an intricate network of patronage involving the Tuscan Medici court in Florence and the Vatican court of Pope Urban VIII in Rome;9 finally, the rhetoric originates to some extent from the fact that he was a gifted writer who poured his heart and soul into this work,
For more details see the appendix (3).
For a brilliant account of this aspect of Galileo's career, see Biagioli (1993).
so much so that many passages achieve a high degree of literary and aesthetic value. Notice that I am not equating rhetoric with the art of deception in general, and the skill of making the weaker argument appear stronger in particular;10 so understood, rhetoric would be an inherently objectionable activity, whereas my definition allows both good and bad rhetoric. Nevertheless, rhetoric does not easily mix or coexist with scientific inquiry, critical reasoning, and methodological reflection; it considerably complicates the proper understanding and evaluation of the text. In this regard, the important thing to do is not to deny the existence of rhetoric in the book, nor to overstress it and neglect the book's other aspects, nor to conflate it with these other aspects, but to learn to detect, analyze, evaluate, and appreciate it. Fortunately, the rhetoric enhances the readability of the book and the enjoyment one can derive from the experience of reading it.
In short, Galileo's Dialogue can and should be read for what it tells us about the history of the Copernican Revolution, the Scientific Revolution, and the Galileo Affair, and for what it can teach us in general about critical reasoning, scientific methodology, and the art of rhetoric.
Excerpted from Galileo on the World Systems by Galileo Galilei Copyright © 1997 by Galileo Galilei. Excerpted by permission.
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|Editorial Preface and Acknowledgments|
|1||Significance of Galileo's Dialogue||1|
|2||The Geostatic Worldview||7|
|3||The Copernican Controversy||28|
|4||The Galileo Affair||38|
|5||Historical Aftermath and Philosophical Prelude||47|
|Selections from Galileo's Dialogue||71|
|Outline of Selections||73|
|To the Discerning Reader|
|2||Natural Motion and Aristotle's Logic||83|
|3||Heavenly Changes and Aristotle's Empiricism||91|
|4||Life on the Moon, and Human versus Divine Understanding||107|
|5||Independent-Mindedness and the Role of Aristotle's Authority||117|
|6||Diurnal Rotation, Simplicity, and Probability||128|
|7||The Case against Terrestrial Rotation and the Value of Critical Reasoning||142|
|8||Vertical Fall, Superposition of Motions, and the Role of Experiments||155|
|9||Extruding Power and the Role of Mathematics||171|
|10||The Deception of the Senses and the Relativity of Motion||212|
|11||Heliocentrism and the Role of the Telescope||221|
|12||The Role of the Bible||245|
|13||Stellar Dimensions and the Concept of Size||247|
|14||Stellar Parallax and the Fruitfulness of a Research Program||264|
|15||The Cause of the Tides and the Inescapability of Error||282|
|App. 1||Critical Reasoning||309|
|App. 2||Methodological Reflection||335|
|App. 3||Varieties of Rhetoric||356|