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The Discovery of Kepler's Laws: The Interaction of Science, Philosophy, and Religion.

This is a historical case study of the conceptual problem of whether and how science, philosophy, and religion interact. It does not examine all of Kepler's work, but focuses on his first two laws of planetary motion; these assert, first, that planets revolve in elliptical orbits around the sun which is located at one of the foci of such ellipses, and, second, that the line connecting the sun and the planet sweeps over equal areas in equal times. Similarly, the book stresses the issue of what role, if any, philosophical and scientific ideas play in scientific discovery; it does not discuss all aspects of the conceptual problem, such as whether scientific discoveries may influence philosophical and religious ideas, although it admits the possibility and indeed the likelihood of this being the case. Its main conclusion is that philosophical and religious ideas played an integral role in Kepler's formulation and justification of the first two laws. This conclusion is well supported, and I regard the author as having made a convincing case, whatever minor reservations of detail I may have.

Furthermore, this key conclusion has some originality in so far as it contrasts with a number of prevailing accounts of Kepler's discoveries. For example, it contrasts with Arthur Koestler's specific view of Kepler as a 'sleepwalker', as well as with the Popperian general thesis denying the existence of a 'logic of discovery'; for, according to Kozhamthadam, the process of Kepler's discovery was a reasonable one. This does not mean that Kepler's first conception of his ideas and subsequent testing of them was 'rational' according to various simple-minded schemas. One of these schemas, suggested by the work of such scholars as Robert Small and J. L. E. Dreyer, would claim that Kepler arrived at his laws by 'curve-fitting', namely by starting with Tycho's empirical data and using them to plot the trajectory of Mars. Another such schema was suggested by Norwood R. Hanson and attributes to Kepler a retroductive or abductive method adapted from Peirce. On the other hand, Kozhamthadam's account also contrasts with those (such as Edwin Burtt's) which portray Kepler as a 'sun-worshipper', exaggerating the role of metaphysical factors and neglecting the role of empirical considerations. However, the author sees himself as attempting to make more precise and more concrete the interpretations of Alexandre Koyre (who did assert that philosophical and religious ideas were crucial to Kepler's discovery) and Gerald Holton (who has spoken of the interaction of science, metaphysics, and theology in Kepler). From this point of view, the author's account, besides being original, is also admirably balanced.

The religious ideas attributed to Kepler are essentially theological ideas. One subgroup of claims are explicitly about God: that He is the creator of the universe; that He is one, simple, and rational; and that He is a geometrician, an active force, and a musician; that human nature is also rational, geometrical, and musical; and that physical nature also reflects the various divine attributes. Kepler's philosophical ideas include such epistemological and methodological principles as realism, quantifiability, causality and sufficient reason, order, unity, harmony, economy, and simplicity.

An example will have to suffice (pp. 190-3). In regard to the second law (which was discovered before the first), recall that the radius vector which sweeps over equal areas in equal times is a line connecting a planet with the sun. This law thus attributes a key role to the sun. Kepler was led to formulate it partly on the basis of empirical considerations. But these were not sufficient or decisive, especially in regard to the question whether or not the earth is a planet. That is, even if the law of equal areas is shown to be true of the planets Mercury, Venus, Mars, Jupiter, and Saturn, the question still remains whether the annual orbital revolution belongs to the earth or to the Sun; this issue is the same as the choice between the Tychonic and the Copernican system. At this juncture, philosophical and religious considerations come into play. The principle of causality leads Kepler to take seriously the problem of the causes of the various motions; and then the principle of simplicity enables him to assert the superiority of the Copernican over the Tychonic system in so far as Copernicus has only one cause of the motions of the five planets and of the earth, whereas Tycho has two causes of motion (the sun for the five planets, and the earth for the annual motion of the solar system around the earth). How did religious ideas play a role? Apparently Kepler found it absurd that the sun should be moved by the earth because the former has a 'much higher ranking than the unimportant earth' (quoted p. 191); this is so presumably because 'there lies hidden in the body of the sun something divine and comparable to our soul' (quoted p. 192); that is, the sun as 'the unmoved mover is the visible parallel of the invisible uncreated creator, i.e., God the Father' (p. 193). This, of course, is the element which some scholars have exaggerated into 'sun-worship', although such an exaggeration may be a way of explaining the persuasive force in Kepler's mind of the just mentioned theological argument for terrestrial heliocentricity. But this brings us to some criticism.

One difficulty stems from the weakness of such religious arguments. The difficulty is that it is unclear how such weak religious arguments fill the gap between Kepler's physical conclusions and the empirical and methodological considerations; that is, it is unclear how they help us understand how Kepler arrived at his discoveries. Another criticism I would make is that the author's case for the interaction between science, philosophy, and religion turns out to be a case for the interaction between scientific ideas, philosophical ideas, and religious ideas; and such 'ideological' interaction is relatively unsurprising. Furthermore, I found the author's classification of various ideas highly implausible; for example, his account of Kepler's 'scientific' ideas includes not only Kepler's views on such physical entities as force and mass, but also his views on the nature of observation, inference, explanation, and scientific method. And since in speaking of religion the author has in mind Kepler's theological ideas, this means that he neglects discussing such things as the fact that some of Kepler's books were placed on the Index by the Catholic Church. The author does discuss Kepler's views on the relationship between scientific enquiry and biblical interpretation, but not in the context of the interaction between science, philosophy, and religion; rather this discussion (pp. 2537) is more in the nature of an afterthought. Thus he manages to attribute to Kepler the following pair of inconsistent views: the novel thesis that the Bible is not a scientific authority (p. 256), and the traditional view that biblical assertions about physical reality are to be interpreted nonliterally only if there is a demonstrably true scientific theory claiming the contrary (p. 257).
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Author:Finocchiaro, Maurice A.
Publication:The British Journal for the Philosophy of Science
Article Type:Book Review
Date:Jun 1, 1996
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