Copernicus and , with an Appendix1 of Translations of Primary Sources

N. M. Swerdlow California Institute of Technology

Robert Westman’s massive book—The Copernican Question. Prognosti- cation, Skepticism, and Celestial Order. Berkeley: University of Cali- fornia Press, 2011. xviii ϩ 681 pp. (double columns), 85 b&w illustra- tions, 7 tables, index—presents a novel thesis and a wealth of material. It is certain to raise questions that go beyond the Copernican. Therefore the Edi- tors are pleased to be able to offer reviews by two people familiar with the doc- uments to which the book refers. The ªrst of these, by Noel Swerdlow, exam- ines the evidence for the book’s central thesis: concern for the defense and improvement of astrology caused Copernicus to build his system. The other re- view, by John Heilbron, considers the workmanship behind the book and related matters, particularly as manifested in its extensive treatment of Galileo.—The editors. For well over half a century research on Copernicus has been dominated by three scholars compared to whom all others vanish into insigniªcance. The ªrst is Edward Rosen, for many years the arbiter of scholarship on Coper- nicus, in countless articles correcting each and every error of those writing on his chosen subject, who, in the ªfth novenium of his research, pub- lished an English translation of De revolutionibus (1978) to take its place among the two published previously. The second is , who, likewise in the ªfth novenium of his research, published An Anno- tated Census of Copernicus’ “De Revolutionibus” (2002), descriptions of all known copies of the 1543 and 1566 editions of Copernicus’s book with transcriptions of some marginal annotation, the product of countless years of travel to libraries and book collectors, an invaluable guide to anyone in-

1. The appendix may be found here: http://www.mitpressjournals.org/doi/pdf/10.1162/ POSC_a_00071

Perspectives on Science 2012, vol. 20, no. 3 ©2012 by The Massachusetts Institute of Technology

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terested in every copy of the 1543 and 1566 editions. The third is Robert S. Westman, who, in articles with countless notes, succeeded Edward Rosen as arbiter of scholarship on Copernicus, and now, in the ªfth novenium of his research, has published an immense study, 700 double- column pages, of “Copernicus’s Problematic,” of astrology and the order of the . As testimony to his industry and erudition, there are ca. 2800 notes (pp. 515–604), many of considerable length, and a bibliography, of mammoth proportions (pp. 605–647), containing more books and articles than I have read in my life. Copernicus explained that he cautiously with- held his book until the fourth novenium, and these scholars, waiting until the ªfth, have given us books of even greater length. Indeed, in reºecting upon Professor Westman’s contribution, my ªrst thought was of the work of Dr. Edward Nares immortalized in Macaulay’s essay Burleigh and His Times, which I cannot too strongly recommend to anyone contemplating the reading of this stupendous volume. This is not to say that there is anything wrong with large books on the history of , after all a large subject with a long history. The six volumes of Delambre’s Histoire de l’astronomie (1817–27) remain the most comprehensive and proªcient ever written, and are still read for their tech- nical content as well as for the author’s custom of improving upon his sources and then lecturing them for their deªciencies. O. Neugebauer’s A History of Ancient Mathematical Astronomy (1975) has every promise of re- maining the authoritative history of this large and diverse subject for years to come, and it too is excellently written with great clarity. And to men- tion something very recent, John North’s Cosmos (2008) has taken its place as the ªnest general and of our time, and can be read with interest from beginning to end. In the case of Pro- fessor Westman’s tome, it is not so much the length as the density, what Macaulay called the speciªc , that distinguishes it from these works. Not that the scientiªc content is in any way demanding; the as- tronomy is elementary and without technical details; although astronomy was then the most mathematical of sciences, there is no ; and the astrology, with mathematics of its own and complex methods of prog- nostication, is likewise elementary. The difªculties are more in the weightiness of the writing. In describing his own work, Professor West- man writes (p. 4): “The present study takes seriously the elements of both sorts of projects—meaning formed at local sites as well as the long-term movements of standards, reasons, and theoretical commitments—seeking a treacherous middle course between the Scylla of internalist conceptual- ism and the Charybdis of the localist turn.” And then (p. 9): “The danger of imposing inappropriate analytic categories points again to the need for a more rigorous historicism, ruthlessly attentive to the pastness of the

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agents’ own categories but also informed and balanced by a judicious cul- tivation of modern epistemic resources.” These are two sentences from the introduction, but they give an idea of the reºections throughout the vol- ume. As a caution, if considering purchasing or reading this book, ªrst read the introduction of twenty-two pages, with many such weighty sen- tences. It is in three sections: “The Historical Problematic,” why the order of the planets and astrology are really important and why no one before has understood it; “Summary and Plan of this Work,” chapter by chapter for eighteen chapters; “Categories of Description and Explanation,” pro- viding “some prior linguistic and conceptual clariªcation.” Whoever can get through the introduction and endure the writing may then attempt the rest of the volume, which I have done, although not always with com- plete success in understanding just what it is the author means to say or why he says it at such great length. Here I can only do my best to report on what I have found. Professor Westman is best known as a disciple of Pierre Duhem, who, in his book To Save the Phenomena (English trans. 1969), described what he called the “Wittenberg School,” which held that, correctly understood, as- tronomical hypotheses in general and Copernicus’s heliocentric theory in particular are models for the purpose of computation with no claim to physical reality. Professor Westman in a number of articles has popular- ized Duhem’s description under the name “Wittenberg Interpretation,” with the distinction that only the heliocentric theory was considered a model for calculation, while Copernicus’s other hypotheses for motions in the heavens could be adapted to geocentric theory. Such an interpre- tation was not that of Copernicus or Tycho or Kepler or Galileo, or of anyone who made an original contribution to astronomy, but may have been favored by some Schulmeister, Pfarrer, and Sternkucker, stargazers, as Luther called makers, “who reckon according to the what will befall you.” Here too Professor Westman writes about Schul- meister, Pfarrer, and Sternkucker of the Wittenberg School, or Interpreta- tion, now with the addition of their devotion to astrology, and he begins his history earlier with a Sternkucker in , with whom we shall also begin.

Dominico Maria di Novara According to Copernicus’s student, , Copernicus, while studying law in from 1496 to 1500, “lived with Dominico Maria, whose theories he learned clearly (rationes plane cognoverat) and whose observations he assisted,” and was “not so much the student as the assistant and witness of the observations of the learned man Dominico Maria.” This was Dominico Maria di Novara (1454–1504), from 1483 to

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1504 professor of astronomy at the university. He was sufªciently distin- guished that a large collection of astrological treatises published in in 1493, beginning with ’s and the commentary of ‘Ali ibn Rid.wan, contains an introductory letter On the Excellence of Astrology addressed to him, and Professor Westman has found a copy with Dominco Maria’s signature. Now, Professor Westman considers Dominico Maria, who he discovers rented his from a notary, which he calls (p. 89) “highly suggestive of unsuspected cultural connections,” of great impor- tance for Copernicus’s concern with astrology, as Dominico Maria pub- lished annual prognostications during the years of his professorship. Pro- fessor Westman has examined some of these, and while it would have been of interest to learn what Dominico Maria did by providing a translation and analysis of one of them, he conªnes his account to a few excerpts on generalities of prognostication. In one excerpt (p. 98), however, which is speciªc, he catches Dominico Maria in an error that does not say much for his competence. According to the translation he has used from a prognos- tication for 1500, Dominico Maria predicted that a lunar eclipse will take place on 5 November with the beginning at 7:30 p.m. and middle at 9 p.m. Professor Westman notes that Copernicus reports his own observa- tion of the same eclipse in Rome on 6 November at two hours after mid- night, concludes that Dominico Maria’s prediction was off by at least ªve hours, and reports that “Novara made no reference to this discrepancy in the next year’s forecast; but it is clear that short-term inaccuracies of this magnitude offered no special difªculty for the credibility of the forecast.” Still, this does not look good for Dominico Maria. Now, at this time, using the or its derivatives, it is sim- ply impossible for the time of a lunar eclipse to be in error by ªve hours— about an hour is possible—except by miscalculation. But that seems un- likely as ’s Kalendarium and Ephemerides, both available to Dominico Maria, give the time of the eclipse as 5 November 14;2 hours, from a noon epoch at the meridian of , and thus 2;2 hours after midnight, close enough to the time of Copernicus’s observation in Rome, dated 6 November in a midnight epoch, or the time in Bologna, which differ only slightly in time from Nuremberg. So what is wrong? It appears that Professor Westman has been ill-served by the translation upon which he relied, less likely by error in the text, for the text surely read, or in- tended, the beginning of the eclipse at 7;30 hours and the middle at 9 hours, meaning not from noon, but from sunset, the usual beginning of the civil day in Italy including Bologna. Since on 5 November sunset in Bologna was at about 5;5 hours after noon, the middle of the eclipse was 9 hours later, at 5:05 p.m. ϩ 9 hours ϭ 2:05 a.m., that is, 2;5 hours after midnight, close enough to Copernicus’s observation in Rome and

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Regiomontanus’s computed time for Nuremberg. So there was no error in Dominico Maria’s prediction, certainly not of ªve hours, and he had no discrepancy to remark on the following year. Aside from his association with Copernicus, Dominico Maria is best known for his one original idea, which may or, more likely, may not be a motion of the earth. This was published in a prognostication for 1489, is well known from its quotation by Giovanni Antonio Magini in his Tabulae secundorum mobilium coelestium (1585), a gigantic set of tables for computing the motions of the , moon, and planets, and Magini’s quotation was re- printed in William Gilbert’s De magnete (1602). Dominico Maria found, by comparing some number of latitudes in Ptolemy’s Geography with more recent determinations, that Ptolemy’s fell short by 1;10°, and to explain this, he proposed a motion, of either the earth or the heavens, from which “places which are now inhabited will at last become deserted, but those which are now boiled beneath the torrid zone will in a long period of time be brought down to our temperate climate, in as much as this exceedingly slow motion is completed in the course of 395,000 years.” Professor West- man refers brieºy to the theory, “that the Earth’s pole had shifted slightly since the time of Ptolemy,” but says no more about it, which is a pity as it is the most interesting thing known about Dominico Maria, shows that he was concerned with the determination of geographical coordinates, a sub- ject then of interest in Italy and Northern Europe, and had the imagina- tion to come up with a really big idea to explain the differences from antiquity. Magini’s account with the quotation from Dominico Maria is translated in the Appendix with some explanation. So much for the learned man Dominico Maria.

Pico della Mirandola against Astrology The year Copernicus came to Bologna, 1496, there was published in that city Giovanni Pico della Mirandola’s Commentationes (Treatises) containing his Disputations against Divinatory Astrology, a huge and vitriolic attack on astrology, surely the most important ever written. Pico (1463–94), the wonder of learning of his age, had recently died with the work unªnished, and the of paper was assembled and edited by his nephew Giovanni Francesco Pico della Mirandola (1470–1533), who later wrote his own at- tack on astrology, with citations of his uncle, in his Examination of the Van- ity of Pagan Learning and the Truth of Christian Doctrine (1520) and other works. Pico’s enormous denunciation, running to 280 closely printed quarto pages in its ªrst edition, was reprinted with corrections to the text in later editions of his Opera omnia; the one modern edition is that of Eugenio Garin with an Italian translation (1946–52, reprinted 2004). There are modern writers on the history of astrology, some of them astrol-

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ogers, who hold that Pico was not attacking all astrology, only bad, in- competent astrology, but from the parts I have read he seems to regard the entire subject as perverse rubbish and is out to annihilate it in any and every way possible. Although much of the work is somewhat dry and scholastic, parts are lively and entertaining, even amusing because so caus- tic and astrology made to look so silly. Pico shows a good knowledge of earlier and contemporary astronomy and astrology, in Greek, , and Hebrew, although one must be careful to distinguish between where he is writing an account of authentic astrology and where he is making up a parody of what he considers its stupidities and the ignorance of astrolo- gers. He certainly read more of the subject, and knew it better, than any- one today. Professor Westman believes that Pico’s work was of great importance to Copernicus, that Copernicus wished to rescue astrology from Pico’s criti- cism, indeed, that Pico’s criticism of the uncertainty of the order of the planets lies at the foundation of Copernicus’s formulation of the heliocen- tric theory. He gives some examples of Pico’s caustic style, from published paraphrases of the summaries of the chapters at the beginning of the book, without examining the contents of the chapters, and then considers Books IX and X, concerning various uncertainties in astronomy and astrology, which he says “have been either ignored or not well understood.” He brieºy mentions disagreements concerning computation of houses, length of the , determination of the time of the vernal equinox, and difªculties of interpretation caused by errors of one degree or even one minute placing a in the wrong zodiacal sign or house. Then the im- portant part: “In Book 10, chapter 4, Pico came to a matter of crucial in- terest here: the order of the planets and the assignment of elemental quali- ties.” It is this chapter, he believes, that led Copernicus to investigate the order of the planets, speciªcally the relation of Mercury and to the sun, from which he formulated the heliocentric theory. The chapter is known at present because of Pico’s report of a supposed transit of Mercury observed by Averroës, cited by Copernicus in De revolutionibus 1.10, and a reference to Maimonides’s citation of Ibn Bajja in The Guide of the Perplexed on the uncertainty of the order of the planets. Now, if this chapter lies at the foundation of Copernicus’s discovery of the order of the planets and the heliocentric theory, of the solution to “Copernicus’s Problematic,” one would expect a complete translation, or at least a complete exposition of its contents. Although it is the fundamental text for his entire book, Pro- fessor Westman seems not to have procured a complete translation, or ex- position of its contents, even with Garin’s Italian translation available, for all he offers is the sort of thing now called a “snippet view” of the chapter, with not many snippets and not all correct. We have translated the com-

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plete chapter in the Appendix, with some comments, and recommend that it be read in its entirety before and along with Professor Westman’s account (pp. 86–87). Here we shall consider Pico’s remarks on astrology and later take up the order of the planets. Pico’s ªrst criticism, of the association of houses with planets and zodi- acal signs, Professor Westman omits entirely, and he begins with snippets on ªre being the ªrst element and Saturn the ªrst planet, but according to the astrologers Saturn is remote from ªre; Mars is the third planet, water the third element, but is not Mars as remote from water as ªre is remote from water? Now, no one actually said these things about Saturn and Mars, which are complete nonsense, as is obvious since Saturn is supposed to be cold and Mars dry, for here Pico is writing a parody of an association of planets with elements, ªre and water, to illustrate his point that “the as- sumption is exceedingly worthless and senseless, that the ªrst in one kind also corresponds to the ªrst of another kind by an afªnity of nature.” And he knows something about this as he had himself earlier revealed (the cor- rect word) an association of the planets with elements, Mars is ªre and Sat- urn water, the opposite of what he writes here, in his Heptaplus (2.2), on the secrets of the seven days of creation, an association he now dismisses as nonsense. Professor Westman, even though he quotes (pp. 132–33) the different association of planets and elements from a published translation of the Heptaplus, does not recognize Pico’s sarcasm in the Disputations, does not recognize deliberate nonsense, and actually takes seriously the associa- tion of Saturn and Mars with ªre and water: “If there was disagreement on the order of the planets, then the principles governing the various asso- ciations of elemental qualities to the planets will be gravely undermined. Beholden to the superior science of astronomy, astrology could no longer be certain of its core association of celestial causes and corresponding ef- fects.” Never mind for the moment that Pico says nothing of “elemental quali- ties,” only of elements, which are not the same thing, and that in a parody of what he considers a ridiculous assumption, is this so? The basic account of the relation of the planets to “elemental qualities,” hot, cold, moist, dry, usually just called qualities, and their effects is Tetrabiblos 1.4, in the translation of Plato of Tivoli, that “the activity of the substance of the sun is to heat and moderately to dry” (substantiae solis opus est calefacere modicumque desiccare), “the greater power of the moon is to moisten, for it is closer to the earth, from which moist vapor ascends from below as far as it” (maior autem lunae vis est humectare, est enim terra proprior a qua vapor humidus ab imo usque ad eam ascendit). Consequently, planets closer to the sun heat and closer to the earth and moon moisten, planets farther from the sun cool and farther from the earth and moon dry, al- though somehow distant, beneªcent Jupiter “at the same time heats and

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moistens” (insimul calefacit et humectat). That is all, a commonplace of ele- mentary astrology. According to Professor Westman (p. 52), “Ptolemy’s entire theoretical astrology was built on these ªxed, elemental qualities, which were thus cemented ªrmly into his planetary ordering.” Really? Actually, the relation Ptolemy describes, planet by planet, is not so much of order as of distance, from the sun and from the earth and moon. And there is a great deal more to Ptolemy’s astrology, including effects of the planets, determined principally by the character of the deities after whom they are named, as earlier for the Babylonians, having nothing to do with either qualities or order, as is obvious to anyone who reads the Tetrabiblos. But let us just consider it. Now, what effect would a change in the order of the planets have? Pro- fessor Westman makes up a chart (p. 57) of “astral-elemental qualities” of the planets in geocentric order and the identical qualities of each planet “reshufºed” in heliocentric order, e.g. Saturn dries and cools, Mercury both “humidiªes” and dries, but he does not explain whether or what al- teration of qualities is required or what he has in mind. Nor does he cite a single source, or any evidence at all, suggesting what effect, if any, the he- liocentric order has on qualities; he just wants to believe it should. But without evidence for such an effect, there is nothing left of Copernicus’s astrological motivation, of “Copernicus’s Problematic,” to defend or cor- rect the “elemental qualities” of the planets by correcting their order, from which he invented the heliocentric theory. “If there was disagreement on the order of the planets, then the principles governing the various associa- tions of elemental qualities to the planets will be gravely undermined.” Well no, and wishing does not make it so. Again and again Professor Westman refers to Pico’s criticism of “the order of the planets and the as- signment of elemental qualities” as, he also says again and again, Coperni- cus’s motivation to defend or save astrology, correcting the order of the planets by inventing the heliocentric theory. But as noted, Pico himself says nothing, not one word, about “the order of the planets and the assignment of elemen- tal qualities,” so there goes the one and only reason, indeed, Professor Westman names no other, for Copernicus, or anyone, to know or care any- thing about it. And no one did. That is the end of “Copernicus’s Problem- atic,” it isn’t even wrong, it does not exist. And with it goes the astrologi- cal origin of the heliocentric theory. There is more. Pico does in fact treat the qualities of planets elsewhere. He had earlier revealed the secret in his Heptaplus (2.3), assigning the stan- dard associations along with those of planets to zodiacal signs, which he must later have decided is, as everything else in astrology, nonsense. For now, in Book X Chapter 13 of the Disputations, in commenting on Tetrabiblos 1.4, he considers the relation of planets to the heat of the sun

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and the moisture of the earth. His objections are based, not on the order of the planets, about which he says nothing, but on their great distances, that vapors from the earth cannot even reach the moon, let alone Venus and Mercury, which must therefore be more dry than moist, contrary to Ptol- emy, and changing their order cannot affect that. (In the heliocentric or- der, Venus and Mercury are still farther from the earth.) And Ptolemy says that Saturn is cold because it is far from the sun and dry because it is far from the vapors from the earth. Pico asks whether, “if Saturn, less remote (than the ) from the sun, is freezing, would not the entire multitude of ªxed stars, since they are more distant from the sun, be drawn asunder by the frozen ice of cold, although it is nevertheless declared that many among them are of a ªery nature?” So here we do have qualities of planets, typically parodied, made fun of, which Pico goes on to consider along with their light and color, disagreements about their speciªc qualities, which were not in fact “ªxed,” whether planets have qualities at all; and in Chapter 14 whether planets, through qualities, have a healthy or un- healthy effect on the air and human body, which he also regards as non- sense. These chapters, Pico’s real treatment of qualities, have nothing to do with order. Professor Westman says nothing about them. But is the order of the planets of signiªcance in astrology? Indeed it is, and in ways quite speciªcally so. These all go back to antiquity, and here we follow the exposition in al-Qabis.i’s Isagoge, near the end of Part 2, translated from Arabic in the twelfth century and still a standard guide to astrology in the ªfteenth. The rulership (principatus) of the months a child spends in the womb of its mother from the time of conception is under the planets in the order: 1. Saturn, 2. Jupiter, 3. Mars, 4. Sun, 5. Venus, 6. Mercury, 7. Moon, 8. Saturn, “and therefore one born in the eighth month does not live because it is born under the power of Saturn,” 9. Jupiter. John of Saxony in his commentary adds that “a child born in the seventh month seeks to go out because the operations of all the planets are com- pleted in it, and those born then can live for the same reason; those born in the eighth month do not live because of the maleªcence of Saturn; and children are commonly born in the ninth month and live because of the beneªcence of Jupiter.” So here is one example of signiªcance of the order of the planets. Then the rulerships of the years of life, earlier in Tetrabiblos 4.10, from the Arabic called the ªrdaria, are assigned to the planets in the opposite order: 1. Moon, from birth through the 4 years of nursing or nur- turing, 2. Mercury for 10 years, 3. Venus for 8 years, 4. Sun for 19 years, 5. Mars for 15 years, 6. Jupiter for 12 years, 7. Saturn until the end of life. Most of these are approximate astronomical periods, going back to the Babylonians: Mercury, 10 years, half of 20 years, as Ptolemy mentions, the cycle 20 years ϭ 63 synodic periods (return to conjunction with the

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sun, for inferior planets superior conjunction, also in 9.10); Venus, 8 years ϭ 5 synodic periods; Sun, 19 years ϭ 235 synodic months; Mars, 15 years ϭ 7 synodic periods; Jupiter, 12 years ϭ 1 zodiacal period. 4 years for the moon is not a period, but 8 years ϭ 99 synodic months is, and Saturn for the last part of life is sometimes given 30 years ϭ 1 zodi- acal period. So here is another example, and it even has an astronomical basis. Finally, there is the most familiar application of the order of the , the planetary hours of the day and days of the week, in which each hour and day has a chronocrator or ruler. The hours may be either equal or, more correctly, seasonal hours, computed by dividing the length of daylight and of night, found in tables, by 12. The planets are taken in descending order: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. We may begin any place in the order and return to Saturn after the moon, but let us begin with Saturn, and we distinguish hours of day and of night. Now, for the ªrst day the hours are numbered: 1. Saturn, 2. Jupiter... 12. Venus, hours of day, and then 1. Mercury, 2. Moon...12.Mars, hours of night. Then, following Mars, the second day: 1. Sun, 2. Venus . . . 12. Saturn, and night, 1. Jupiter, 2. Mars...12.Mercury. And the third day, following Mercury, begins with 1. Moon, and so on. When we take the ªrst hour of each day, we have the order of the planetary days of the week, partially disguised by Germanic deities in English: Dies Saturnius (Saturday), Dies Solis (Sunday), Dies Lunae (Monday), Dies Martis (Tues- day), Dies Mercurii (Wednesday), Dies Jovis (Thursday), Dies Veneris (Fri- day). Pico does consider planetary hours and days in the ªrst part of Book X Chapter 15, which is translated in the Appendix. Of course he considers it rubbish, and one of his refutations is none other than the uncertainty of the order of the spheres, of the planets. So here we do have an aspect of as- trology, of which Pico takes note, in which the order of the planets is signiªcant, and one may wonder whether a defense of astrology, by Coper- nicus or anyone else, would require changing the order of the planets, the order of the days of the week, or both. One would think Professor Westman would say something about planetary hours and days and Pico’s objection based upon order, but he is silent. (He has never heard of either. Commenting on ’s explanation of planetary hours and days, which is clear and correct, he writes (p. 212): “Clavius’s planetary or- dering does not map neatly over the sequence of weekdays; but with some nimble, ad hoc juggling he managed to produce a ªt. That he thought it plausible to include such an argument may perhaps be explained by the need to add spice to a student textbook, perhaps a mnemonic for remem- bering the planets and their ordering.”) Pico goes on to criticize the ruler-

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ships of years of life by the planets, but does not mention the months in the womb. Professor Westman mentions neither. So much for Pico’s criti- cism of astrology.

The Order of the Planets according to Pico, Regiomontanus, and Copernicus Pico’s account of the uncertainty of the order of the planets is thorough and interesting, based upon his reading of Greek, Latin, and Hebrew sources, although he does not appear to know Regiomontanus’s account in the Epitome of the Almagest, of which there were then copies in manuscript. His demands are strict, holding that the order is in dispute, not only of the sun, Venus, and Mercury, but also of the planets above the sun, Mars, Jupiter, and Saturn, for the order of none of these can be determined by certain and mathematical reasons without measurement of parallax. Ptol- emy also, in Almagest 9.1, says that none of these stars has a noticeable par- allax, which is the only phenomenon from which their distances can be found. All other reasons for determining order Pico dismisses as insub- stantial and disputable, starting with Ptolemy’s criterion of placing the sun between the planets that reach opposition from those that reach only a limited elongation, because the moon, which is lowest of all, reaches op- position. He mentions Jabir ibn Aºah., who, in his Correction of the Alma- gest wrote a lengthy analysis placing Mercury and Venus above the sun, be- cause they do not have a detectable parallax, and gives a cryptic account of al-Bit.ruji’s placing Venus above the sun because, according to his method of measuring planetary motion opposite to the diurnal rotation, Venus falls behind the diurnal motion more slowly than the sun and Mercury, something Regiomontanus explains more clearly. In considering the ab- sence of transits of Venus, and Mercury, he is skeptical of explanations of why they are not seen, including the possibility that they are translucent or self-luminous, although he does not mention that they may not be pass- ing in front of the sun because of their latitude, and it is here that he cites without comment Averroës’s report of a transit of Mercury, perhaps be- cause, contradicting everyone else, it just increases uncertainty. Since Pico’s criticism of the order of the planets is supposed to be the source of “Copernicus’s Problematic,” one would expect Professor Westman to ex- plain it at length. But he does nothing more than reproduce a few snip- pets, some in incorrect translation making little sense, does not know that “Moses the Egyptian” is Maimonides and “Abubachis” is Ibn Bajja, or that Pico considers uncertain the order of, not just the sun, Venus, and Mer- cury, but also Mars, Jupiter, and Saturn, an important point he makes twice, meaning that Pico does not even consider period an indicator of or- der, for only parallax can determine order, a very strict standard he applies

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to, not just three, but all of the planets, of which Professor Westman is unaware. Regiomontanus’s account of the order of the planets in the Epitome of the Almagest 9.1, translated in full in the Appendix, is similar to Pico’s in con- sidering at some length why it is that transits of Venus and Mercury are not seen if they are below the sun. His principal differences concern the small size of Venus from al-Battani—Mercury is smaller still—and that when in conjunction with the sun the planets may not lie on the line from the eye to the center of the sun, meaning that their latitudes exceed the apparent radius of the sun. He does not mention Ptolemy’s criterion of the sun’s dividing the planets reaching opposition from those reaching a limited elongation, nor Jabir’s placing Venus and Mercury above the sun, but he does give a somewhat fuller explanation, still condensed, of why al-Bit.ruji placed Venus above the sun (explained in the note on the translation in the Appendix). The most notable difference is his use of the distance between the moon and sun leaving space for the spheres of Mer- cury and Venus, with the greatest distance of the moon of about 64re (earth radii) and the least distance of the sun of about 1070re taken from al-Battani. Since nature does not intend the intervening space of about 1006re to be empty, it will by a natural proportion be claimed by the two spheres of Venus and Mercury. However, there is no certain way of deter- mining which of these is above the other, for Mercury can only be seen near greatest elongation where its parallax is too small to determine accu- rately since neither instruments nor the computation of its motion are suf- ªciently accurate. And the same uncertainty holds for Venus. Hence, while Regiomontanus accepts the interval between the moon and sun, and evidently the principle of contiguous spheres, to show that Mercury and Venus are below the sun, he leaves open the question of their own order. Professor Westman says that the order of the planets “received scant dis- cussion” from Regiomontanus, which might seem unfair to someone who has read it, merely repeating the snippet that it is a matter of “contro- versy,” and for some reason he denies that Regiomontanus considers tran- sits of the sun by Mercury and Venus. Copernicus’s own treatment of the geocentric order of the planets, in De revolutionibus 1.10, drawn from Pico and Regiomontanus, is readily avail- able for comparison with the texts translated here, from which his debt to both is obvious. But he also has criticisms of his own, the most interesting based upon distances of the planets from the moon to the sun in the trans- lation of Proclus’s Hypotyposis in Georgio Valla’s De expetendis et fugiendis re- bus (On Things to be Sought and Avoided, 1501, 18.23), a huge compendium of Greek learning mostly from late sources. At the end of the Hypotyposis, Proclus gives answers to ten questions set out at the beginning, the sev-

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enth of which concerns the order of the planets. The order is demonstrated by distances based upon the principle of contiguous spheres in Ptolemy’s Planetary Hypotheses, from which Ptolemy computed distances, but Ptol- emy is not mentioned and the computation, of unknown origin, follows more strictly the relative least and greatest distances in the Almagest. Co- pernicus attributes the distances to “those who place Venus and Mercury below the sun from the ample size (amplitudine) of the space which they ªnd between the sun and moon,” and there are some errors in his analysis. Between the greatest distance of the moon 641 r and the least distance of 6 e the sun 1160re is an interval of 1096re. Lest such an immense space remain empty, from the distances between the apsides, from which they compute the thickness of the spheres, they ªnd that the spheres, of Mercury and Ve- nus, occupy very nearly the same numerical quantities (numeros). Thus, the distance between the apsides of Mercury, the difference of greatest and least distance, is about 1771r , leaving the interval of Venus 1096r Ϫ 2 e e 1771r ϭ 9181r ≈ 920r , for which Copernicus gives very nearly 910r . 2 e 2 e e e (Correctly 1771r is the greatest distance of Mercury, so the interval 2 e should be 1160r Ϫ 1771r ϭ 9821r , and he does not give the greatest e 2 e 2 e distance of Venus according to Proclus of 1150re.) Thus, the large space between the spheres of the moon and sun is taken to be ªlled by the spheres of Mercury and Venus. But this too produces a large space, for he notes that the diameter of the epicycle (text: circuli) of Venus, by which it digresses from the sun about 45° on each side, must be six times greater than the distance from the earth to its lowest . (The calculation (1 ϩ sin 45°)/(1 Ϫ sin 45°) ≈ 1.71/0.29 ≈ 6/1 is of the ratio of Venus’s greatest to least distance. The ratio of the diameter of the epicycle to the least dis- tance would be (2 sin 45°)/(1 Ϫ sin 45°) ≈ 1.41/0.29 ≈ 5/1.) “What then will they say is contained in that entire space (of the epicycle of Venus), so much greater than the space that would contain the earth, air, aether, the moon, and Mercury, and beyond which that immense epicycle of Venus would occupy if it revolved around the earth at rest?” The cause of his con- cern is evident in Figure 1, drawn without eccentricities but more or less to scale, in which the epicycle of Venus is huge, far larger than the space containing everything within the sphere of Mercury, just as Copernicus says. And that is the point, interesting, original, and effective, of his anal- ysis and criticism of the order and distances of the inferior planets deter- mined by contiguous spheres. Professor Westman mentions it only brieºy (p. 104) without explanation. If indeed Copernicus was concerned about the geocentric order of the planets, how would this lead him to the heliocentric theory? Professor Westman has little to say about this aside from quoting some snippets concerning the relation of the motions of the planets to the motion of the

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Figure 1. Relative sizes of the sphere of the moon, the spheres and epicycles of Mercury and Venus, and the sphere of the sun determined by contiguous spheres.

sun (p. 50), which he calls “shared motions,” from the published English translation of Georg Peurbach’s Theoricae novae planetarum, a standard text that Copernicus must have known in one of several printings before the end of the ªfteenth century. But he quotes the wrong snippets, missing the essential parts, and, aside from reproducing some ªgures from publi- cations of others on the relation of geocentric and heliocentric models (pp. 59–60), never explains the relations to the motion of the sun, or the relation of geocentric and heliocentric models, or how Copernicus could ªnd these relations let alone derive the heliocentric theory. If this is im- portant, it is also important to get it right. Peurbach’s pertinent sections are translated in the Appendix with explanations of the relation of the mo- tions of the planets to the motion of the sun and of the relation of geocen- tric and heliocentric models. These relations do not in themselves show how Copernicus was led to the heliocentric theory, which came later, after he knew a more detailed consideration of the relations of the motions in the Epitome of the Almagest, but they are essential for understanding the re- lation of geocentric and heliocentric theory.

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Copernicus and Astrology Was Copernicus concerned with astrology? There is not a single reference to astrology in his surviving writings or correspondence, not a single horo- scope or prognostication is attributed to him. Since he had read at least parts of Pico’s disputation against astrology, he too could have considered it perverse nonsense and ignored it entirely. But neither did he write a word against it. Still, since everyone of his age concerned with astronomy was also concerned with astrology—I know of no exceptions—these argu- ments from silence do not carry much weight. While a student at Cracow, he acquired copies of the Alfonsine Tables, for computation of the sun, moon, planets, and eclipses, Regiomontanus’s Tabulae directionum, for spherical astronomy, both used nearly exclusively for astrology, and ‘Ali ibn Abi ’r-Rijal’s In iudiciis astrorum, the most comprehensive astrological treatise translated from Arabic. So it appears that he was interested and competent in these subjects and may also have attended lectures on as- tronomy and astrology, which were given regularly. Professor Westman takes note of this, and also considers signiªcant his own approach “through the back door,” the “culture of astrological prognostication” when Copernicus was in Bologna with Dominico Maria. All of this is rea- sonable, but is there anything more speciªc showing Copernicus’s interest in astrology? One cannot appeal to Copernicus’s wish to correct the order of the planets to rescue astrology from Pico’s criticism of “the order of the planets and the assignment of elemental qualities” because, as we have seen, Pico wrote nothing of the kind and neither did anyone else. Now, there is in fact a work by Copernicus applicable ªrst and foremost to as- trology, which provides evidence that he must have been concerned with it, but it comes from a much later period and is lost. Nevertheless, there can be no doubt of its signiªcance. Copernicus’s work was an almanac, an , described in a letter of 15 October 1535 by Bernard Wapowski, who sent it for publication to Sigismund von Herberstein in . Wapowski calls it something new and long desired by learned men, an almanac with the truest and ªnest corrected motions of the planets, which differ greatly from the common almanac, calculated from new tables by , a great , who added that for the correction of the motions of the planets, it is necessary to allow some motion to the earth, an opinion he has held for many years, and he maintains that the earth moves insensibly. Some of the aspects, Wapowski says, were omitted or copied incorrectly, but these can easily be added and corrected since the motions are correct. The almanac must have been in standard form, with longitudes of the sun, moon, planets, and ascending node on the left page and aspects to each other on the facing right page of the opening for each month of the year,

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presumably 1536. Wapowski wishes the almanac to be distributed or printed so that almanac makers and astronomers will acknowledge their errors and the errors of their tables, since neither meteorological prog- nostications nor annual can be done correctly without true mo- tions and aspects of the planets. The letter shows that Copernicus in- tended his work to be useful for astrology, the purpose of ephemerides with aspects, which perhaps would encourage interest in his new theory, as Wapowski’s remark about the necessity of the motion of the earth indi- cates, although the heliocentric theory and the motion of the earth would not be evident from an ephemeris by itself. Or perhaps he just wished to give Sternkucker a more accurate ephemeris with aspects. That Wapowski believed the ephemeris more correct than common , in which Mercury can be in error by 15° and dates of aspects by several weeks, is ei- ther what Copernicus told him or his own recognition of differences from other ephemerides. Alas, Wapowski died on 21 November, there was no publication, and the ephemeris has never been found. The letter, quite in- teresting and amusing, and the most direct evidence for Copernicus’s interest in astrology, is translated in the Appendix. Considering its sig- niªcance, Professor Westman’s treatment of this letter is curious; he does not say a word about it. The other evidence for Copernicus’s interest in astrology is later still and is indirect, an account of the astrological signiªcance of the motion of the center of the earth’s sphere, the mean sun, in the small circle that pro- duces long-period variation of the earth’s eccentricity and direction of apsidal line in Copernicus’s solar theory, by Rheticus in the Narratio prima (1540), his account of Copernicus’s new astronomy in De revolutionibus. It is an example of astrological history, the application of aspects of the plan- ets within zodiacal signs to determine the character of historical events, the best known being Great Conjunctions of Jupiter and Saturn, about every 20 years, their shift of triplicities, three zodiacal signs at trine as- pect, in about 240 years, and their return to the original triplicity, in about 960 years, although the periods vary if true motions are considered. These conjunctions in their zodiacal signs are related to the rise and fall of kingdoms and religions, called “sects” or “laws,” and they commanded se- rious attention, and alarm, in the ªfteenth and sixteenth centuries. In the variation of eccentricity from the motion of the center of the earth’s sphere in its small circle, with a period of 3434 Egyptian years, Rheticus found a long-period motion he believed even more signiªcant for the rise and fall of kingdoms and religions, and he writes a wonderful account of it from the Creation, through the Roman Empire, the rise and predicted fall of Is- lam, to the Coming of Christ, a period of nearly 7000 years. Whether Co-

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pernicus himself was interested in astrological history and believed his new theory could contribute to it so spectacularly is not known. But since Rheticus wrote the Narratio prima while visiting Copernicus, his “teacher,” as he always refers to him, it is surely unkind to think he in- cluded subjects to which Copernicus was not favorable and withheld his account from his teacher’s inspection and approval. So even if the chronol- ogy is Rheticus’s own contribution, there is no reason to believe it con- trary to Copernicus’s own opinion of astrological history. Professor Westman agrees, and seems to believe that hardly anyone else does, for he argues strenuously against those who hold that Copernicus op- posed astrological history or astrology in general. He writes about Rheti- cus’s account with quotation of some snippets (pp. 118–20), but aside from reproducing a ªgure from the French edition and translation of the Narratio prima, does not explain Copernicus’s model for the motion of the center of the earth’s sphere or the computation of the chronology of the historical events in Rheticus’s account, astrologically the important part. Rheticus’s account is translated in the Appendix with an explanation of Copernicus’s model and Rheticus’s chronology of world history. There is another document, closely related to the Narratio Prima and worthy of attention, a dedicatory letter in the second edition, , 1541, from Rheticus’s former teacher Achilles Pirmin Gasser, a physician with interests in astronomy, astrology, and geography, to Georg Vögelin. Pro- fessor Westman quotes some snippets from it, not all correctly, and re- gards it as intended to encourage the interest of astrological physicians, as Vögelin too was a physician (pp. 116–17). I have nothing against astro- logical physicians, but the contents of the letter are entirely astronomical and of considerably more interest. The letter is, after the Narratio prima it- self, the earliest approval of Copernicus’s astronomy, even if “opposed to the common theories of the schools and, as monks would say, heretical,” which means the heliocentric theory and the motions of the earth. It shows great admiration for Copernicus and for what he has done, is quaint enough to be entertaining, and is translated in the Appendix. Now, a principal subject of Professor Westman’s book is the importance of astrology, for at the time of Copernicus, as remarked earlier, and until sometime in the seventeenth century, to the best of my knowledge there was no one concerned with astronomy who was not also concerned with astrology, aside from those few who opposed astrology for religious rea- sons, which does not mean that they did not also take advantage of it. As- trology is a very large subject, in which there is much of interest in both its mathematical part and judicial part. Its most well known practice, al- though not its most common, was the casting of horoscopes, for nativities,

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foundations of cities and building, revolutions of years, which are anniver- saries of nativities and foundations, for astronomical phenomena, as eclipses and entries of the sun into zodiacal signs, for astrological history, as Great Conjunctions, near historical events. All of these require the use of astronomical tables or ephemerides for the sun, moon, and planets, and tables for spherical astronomy, for computations of houses, for which there were various methods, and for “directions,” differences of right or oblique ascension between a signiªcator and a promissor, converted to years by let- ting each degree stand for one year, to extend a to events at speciªc ages throughout life, also done through “profections,” related to revolutions of years. For houses and directions, since the spherical compu- tations are laborious, there were special tables. Regiomontanus’s Tabulae directionum profectionumque, its full name, the most frequently used, were expanded in larger tables by Reinhold and Magini, and handy tables of houses were included in ephemerides. The literature on the judicial part, the interpretation, of all of these, is enormous, the largest and most com- plicated subjects in astrology, directions in particular, receiving the atten- tion of those reputed to be the most learned astrologers. But the most common applications of astrology, of astrology for every- body, were not as complex. These were the subjects of annual almanacs, most the work of Sternkucker, printed in increasing numbers from 1460 on and among the most common of all publications for some two hundred years. Almanacs were concerned above all with “changes of air,” the weather, and “elections,” favorable times for all the activities of life, both determined by aspects of planets and their locations within zodiacal signs. This is the reason aspects were included in Copernicus’s ephemeris de- scribed by Wapowski; ephemerides often included guides to both of these, and they were explained in texts on astrology from elementary to ad- vanced. The general principle of weather prognostication, in addition to the season, shown by the zodiacal sign of the sun, concerns aspects of plan- ets within zodiacal signs, considering the qualities of the signs, hot, cold, moist, dry, which in different combinations can produce anything from extreme heat and cold to clouds, rain, and snow. An example from later printings of Regiomontanus’s Ephemerides: “A conjunction of Saturn with Jupiter or another planet, and for many days before and after on account of the slowness of their drawing apart, in ªery signs (, , ) brings forth extreme drought, in watery signs (, , ) foretells continuous ºoods of waters and exceptional deluges.” Elections likewise concern aspects of planets within zodiacal signs, especially of the moon, which each month passes through every sign and every aspect to every planet, but now it is other characteristics of planets and signs: mas-

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culine or feminine, diurnal or nocturnal, beneªcent or maleªcent, the part of the body and humor with which each is identiªed, and many others. The most important elections were medicinal procedures, as phlebotomy, taking pills and potions, applying ointments, taking medicinal baths, spe- ciªed for various disorders and parts of the body, and for ages, from child- hood to old age. The familiar ªgure of a human body with zodiacal signs over the parts, a melothesia, from Aries at the head to at the feet, shows which part not to bleed when the moon is in that sign. An example for phlebotomy: “If you wish to know the suitable time for letting blood, note these aspects: If the moon is together with Saturn in a suitable sign, or at least looks upon Jupiter or Venus or Mercury in a sextile or trine as- pect, we consider it the best time to let blood. And the suitable signs are Aries and Sagittarius, beneªcial for phlegmatics, Aquarius and the ªrst half of for melancholics, Cancer and Pisces for cholerics; but , Leo, the second half of Libra, and Scorpio are not suitable.” Among elec- tions of general concern were activities both important and mundane, as cutting hair or nails, marriage, conceiving children, weaning children, sending children to school, buying and putting on new clothes, plowing ªelds, planting crops, hiring and purchasing livestock, laying foundations of buildings, buying and selling, borrowing and lending, or other com- mercial ventures, receiving or transferring hereditary property, dignities, and ofªces, in short, every activity of life. In a study of the signiªcance of astrology to Copernicus and to astron- omy in general, one would expect an explanation of the practice of astrol- ogy, the mathematical part and the judicial part, for these were not only ubiquitous, the way people lived, but are truly interesting. Over and over again, as frequently as he insists upon the importance of Pico della Mirandola’s criticism of “the order of the planets and the assignment of el- emental qualities,” Professor Westman insists upon the importance of as- trology. He cites astrological books, has had some snippets translated, and relies upon some published translations. Yet I am at a loss to understand why he does not explain these subjects, for he explains next to nothing— there is a brief note on houses (p. 527n54), making no sense and mostly wrong—especially considering that books listed in his bibliography con- tain everything one could wish to know about all aspects of astrology.

Copernicus and Astronomy If there are questions about Copernicus’s interest in astrology, there are none about his interest in astronomy. Copernicus’s accomplishment in as- tronomy was considerable, far beyond anyone of his age, indeed, he was the only person of his age who made an original contribution to astron-

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omy at all. In his early work, the Commentariolus, written prior to 1514 and probably not before 1510, he not only explained the heliocentric the- ory for the motion of the earth and planets about the mean sun, the center of the earth’s sphere, but also models for, in order: the apparent motion of the sun, precession of the equinoxes, motion of the moon in longitude and latitude, motions of the planets in longitude and latitude for superior and inferior planets, which are different. In setting out the heliocentric order of the spheres of the planets, he does not mention that he has done any- thing remarkable or signiªcant, or provided the solution to an old prob- lem, or that it was his primary concern or even of any concern. Perhaps that was a secret. Instead, he repeatedly says that the intention of his new theory is to preserve the uniform circular motion violated by Ptolemy’s models. That was not a secret. Copernicus’s guide to mathematical astron- omy was Regiomontanus’s Epitome of the Almagest, printed in 1496, and he seems not yet to have known the Almagest, printed in 1515. The models for the moon and the ªrst inequality of the planets, preserving uniform circular motion, are based upon those of astronomers of what has come to be called the “Maragha School,” from the observatory of Maragha in Per- sia, in particular Ibn ash-Shat.ir of Damascus. The latitude theory uses a device of Nasir ad-Dinat.-T.usi. The transmission of their inventions, probably to Italy, and in what form Copernicus learned of them are not known, but the principles of his models are identical, ruling out inde- pendent discovery. There are deªciencies in Commentariolus that Coperni- cus later corrected. His new theory is set out in a series of postulates, al- though he certainly considered it true, numerical parameters are adapted principally from the Alfonsine Tables, of doubtful accuracy, and errors in the models for the inferior planets suggest misunderstandings of his sources. His accomplishment in De revolutionibus was virtually a new Almagest, for which Copernicus was recognized as a second Ptolemy. De revolutionibus is a comprehensive treatise on mathematical astronomy: plane and spheri- cal , spherical astronomy, a catalogue of coordinates of stars adapted from Ptolemy’s; precession of the equinoxes and obliquity of the with long-period inequalities; solar theory with long-period in- equalities; lunar theory, distance and parallax of the sun and moon, appar- ent diameter of the sun, moon, and earth’s shadow, required for the follow- ing treatment of eclipses; planetary theory in longitude, stations and retrogradation; and last planetary theory in latitude. The title page carries in Greek the motto said to have been written over the door of Plato’s Academy, “Let no one ignorant of (ageometretos) enter.” Whether this was included at Copernicus’s request is not known; it is a stronger

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warning than his “mathematics is written for ” directed to interpreters of Scripture. But it seems appropriate, as after the ªrst eleven chapters of Book I, the general description of the world, with the reasons for the motions of the earth and the heliocentric theory, the remainder of the six books is entirely mathematical. And concerning planetary theory in particular: descriptions of models, adapted from those of Maragha, but now correctly and with alterations from those of the Commentariolus; deri- vations of parameters from observations, at great length, the ªrst inclusive derivations since Ptolemy; and explanations of the computation and use of the tables. It is notable that the tables are geocentric in form, and in using them a heliocentric longitude or latitude never appears as a step in the cal- culation. Copernicus drew upon a thorough knowledge of the Almagest and the Epitome of the Almagest, which can be seen on nearly every page, to a lesser extent upon a few other works, as the Alfonsine Tables and the Ta- bulae directionum, and of course there is much that is his own, for he was, as noted earlier, the only original astronomer of his age. Considering the originality and importance of Copernicus’s work, and the interest shown in it through the rest of the sixteenth and early seven- teenth centuries, even by those who did not care for the heliocentric the- ory, one would expect that an exposition of De revolutionibus would be es- sential to so authoritative a study of Copernicus. I cannot but wonder why Professor Westman does nothing of the kind, writes next to nothing of Copernicus’s astronomy, of the content of De revolutionibus. The few pages treated in any detail are the dedication to Pope Paul III, about which he has written articles, especially the words monstrum from Horace’s Ars po- etica and symmetria, and Osiander’s note to the reader about hypotheses (pp. 133–39, 128–30, etc.). Why should this be? I wish it were not so, but the failing appears to be the neglect of mathematics, without which little of Copernicus’s astronomy can be understood, in accordance with the notice on the title page. There is a well-known article by O. Neugebauer, “On the Planetary Theory of Copernicus” (1968), all of fourteen pages long, with more about Copernicus’s astronomy than all of Professor West- man’s book. It does not appear in the vast bibliography and seems not to have been read, which is a pity as it contains much of value, including cor- rection of common errors, as that Copernicus’s planetary models are with- out the equant, which Professor Westman repeats again and again as “equantless,” although it has been shown to be false in Neugebauer’s arti- cle and other literature listed in the bibliography but also unread. There is also little acquaintance with the Almagest or the Epitome of the Almagest, both mathematical and essential to understanding Copernicus’s astron- omy, and all astronomy in the period from Copernicus to Kepler. There is

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more on the astronomy of this period, with better understanding, in the three chapters on Copernicus, Tycho, and Kepler of J. L. E. Dreyer’s A History of Astronomy from Thales to Kepler (1906).

The Long Sixteenth Century After ªnishing Pico and Copernicus, this history of what Professor Westman calls “the long sixteenth century” declines somewhat from its previous level and seems to lose its way as it wanders around and around, roughly chronologically, through a variety of lesser-known ªgures, includ- ing Schulmeister, Pfarrer, and Sternkucker of the Wittenberg School, or Interpretation, as well as the most well-known, Tycho, Kepler, and Gali- leo. Most still follow Ptolemaic theory, a few Copernican or Tychonic, and since other than that there is little concern with the order of the planets, and none with adapting the order of the planets to astrology or astrology to the order of the planets, it is difªcult to understand the purpose of the remaining fourteen chapters, appearing to belong to other books or arti- cles and here just ªlling pages. The explanation of astronomy and astrol- ogy remains slight, the numerous sources cited hardly, if at all, read. Pico’s criticism of astrology is still a nuisance to some astrologers, but not for the order of the planets or “elemental qualities.” For this absence of concern with the order of the planets or Pico, Professor Westman offers various reasons, for example (p. 209): “Like the majority of his contemporaries, Clavius did not know that Copernicus intended his proposed arrangement as the solution to the Piconian critique of celestial order.” One wonders which of Clavius’s contemporaries did know. Since these chapters have lit- tle to do with the principal subject of the book, I shall consider brieºy only Tycho and Kepler and their presumed association with Pico. The treatment of Tycho, “The Tychonian Problematic,” is curious. Tycho was the greatest astronomer of his age, who, with his assistants, car- ried out the most extensive program of observations, using the ªnest in- struments, of the sun, moon, planets, and stars, of a quantity, many thou- sands, and accuracy never before achieved, with the intention of a complete reform of astronomy. He did not live to complete the reform, but he did complete a new solar theory, the ªrst new catalogue of stars since Ptolemy, and with the help of Christian Longomontanus a new lunar theory; the intended planetary theory was eventually completed in Longo- montanus’s Astronomia Danica (1622). He also said he devised from experi- ence a method for meteorological prognostication and nativities differing from that in use, but intends to keep it secret. The most Professor West- man can say for Tycho’s reform of astronomy (p. 248): “As early as 1574, Tycho had arrived at a juncture bearing residues from the Piconian prob- lematic of Copernicus’s Bologna period. Like Copernicus, he had con-

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vinced himself that the best defense of astrology, a conjectural discipline, would be through some kind of reform of astronomy.” The evidence for this “juncture bearing residues,” a single reference to Pico as criticism of bad astrologers in Tycho’s Oration on the Mathematical Sciences of 1574 (p. 246), his only reference to Pico, would surprise Tycho. And I am sur- prised to learn that Tycho expended twenty-ªve years of unremitting work and his entire fortune to defend astrology through some kind of reform of astronomy. Instead of an examination of Tycho’s astronomy, al- most entirely mathematical and, it must be confessed, excruciatingly de- tailed, what we have here is Tycho’s nobility, something on the Tychonic theory—leaving out the essential property, that with respect to the direc- tion of the sun’s motion about the earth, the superior and inferior planets move in opposite directions—some pages (pp. 250–58) on “The Comet of 1577 and its Discursive Space,” and then (pp. 288–300) on “Negoti- ating the Spheres’ Ontology,” which seems to mean whether they are re- ally there. There is a review of “intercourtly letters” between Tycho and Christopher Rothmann on this subject, already treated in secondary litera- ture, “deeply grounded in the mutual epistemic beneªts that had moti- vated the initial interchange,” in which “common disciplinary identity provided a point of social and epistemic reference that could mitigate ulti- mately profound disagreements,” that Rothmann was a Copernican and Tycho was not. All of this does little justice to Tycho. The consideration of Kepler begins at a difªcult time, as Professor Westman explains (pp. 309–10): “With the sixteenth century nearing a close and the expectation of the end of the world ever powerful among Lu- therans, the attractions of Copernicus’s theory remained, at best, tenuous.” And besides the end of the world: “Other than common scriptural and physical objections, there is another important explanation for the neglect of the Copernican ordering scheme. No one had found in the arrangement a ready resolution to the problem of the variation in the strengths of the astral powers.” Was anyone looking? Alas, no one understood the secret that the heliocentric theory was the solution to the order of the planets and astrology, and again we are told: “Reassigning the order of planetary forces—inserting the Earth and removing the Sun and Moon among the planets—amounted to overthrowing one of the traditional theoretical foundations of astrology.” Into this desolation stepped Kepler, speciªcally “Kepler’s Physical-Astrological Problematic and Pico.” What could this be? In 1593 Kepler, then a student at Tübingen, wrote, as he later de- scribed it in the Mysterium Cosmographicum, “a carefully prepared disputa- tion on the ªrst motion, that it takes place through the rotation of the earth, in which, as Copernicus for mathematical reasons, I for physical, or rather, metaphysical reasons also attributed the solar motion to the same

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earth.” A substantial fragment of this disputation survives, and it contains principles that Kepler continued to hold and enlarge for the rest of his life, most notably that the sun is the source of motion in the planetary system. To summarize: The most excellent of all bodies in the world is the sun, the entire essence of which is the purest light, the ruler of the planets by mo- tion, the heart of the world by virtue, in which God the Greatest Artisan, if He took delight in a corporeal abode and could be contained in a place, would dwell with His blessed angels. The sun is placed immobile in the middle of the world as the very mover, from which, as though from the center and, as it were, the heart of the world, it extends itself outward very uniformly through forces (energeias) to all the surrounding spheres, so that the closer move more swiftly with shorter periods and the farther more slowly with longer periods, while the ªxed stars at a nearly inªnite dis- tance do not move at all. It does not appear that Professor Westman has had Kepler’s disputation translated, for he says nothing of the part summarized above, the essential part, and all he quotes of it is a passage on the sun paraphrased by E. A. Burtt, with whom he disagrees. Nevertheless, on the basis of three snip- pets he calls “vivid passages” from Pico in an article by L. Valcke (1996), on heaven acting by motion and light, on light and heat from the sun, on light and heat from heaven, which he says “recall our earlier discussion of Pico and Copernicus,” through pages of circuitous reasoning (pp. 314– 24), including speculation on what is missing from Kepler’s disputation, without knowing what is in it, and other questions without answers, he reveals the secret that “a Copernicanizing and astrologizing Kepler” de- rived the principle that the sun is the source of motion from Pico, as he fe- licitously puts it, “Kepler had found a gold nugget in Pico’s dung heap.” However, when the vivid passages from Pico are read with their adjacent sentences, not only do they have nothing to do with Kepler’s disputation, they contradict it. Speciªcally, Pico writes (Book III Chapter 9), “all motions depend upon the ªrst motion just as the motion of an animal from the motion of the heart.” And the “ªrst motion” is not from the sun, which is not mentioned, but clearly, and conventionally, the diurnal rota- tion of the heavens, for Pico says that as well as differing in speed and number of motions, “those (stars) occupying higher positions than others also traverse greater distances” (haec illis sublimiores obtinent sedes et ampliora spacia peragunt), which is exactly what the diurnal rotation of the heavens produces, higher bodies move greater distances. There is no way of deriv- ing Kepler’s cause of motion in the sun from this, from anything by Pico. The remaining pages and pages on Kepler are not better, with slight un- derstanding, only snippets from the original sources, nothing technical or mathematical, and, beneath all the density of the writing, turning the

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work of the most profound of astronomers into something trivial. Con- sidering what can be learned from the extensive, excellent secondary liter- ature on Kepler’s astronomy and astrology, one would expect a more proªcient account. Having struggled through twelve chapters, 350 long pages with ca. 1800 notes, it was in a state of exhaustion that I reached Galileo. Fortu- nately, the section on Galileo is treated here in a separate review. But there is one further subject we must take up, a general one. As mentioned earlier, Professor Westman has succeeded Edward Rosen as arbiter of scholarship on Copernicus, and here he extends his judgment to everyone who has writ- ten on the subjects of his history, often at length, even though many of the objects of his strictures are fallen into obscurity or dead. He does not ap- pear to grasp that it is all right to say what you wish without scolding ev- eryone who said something different. The particular object of his animus, however, is Thomas Kuhn, for The (1957) and The Structure of Scientiªc Revolutions (1970), on whom he earlier wrote a review ar- ticle (Isis 85, 1994) and now rebukes again and again (beginning on p. 3). His attitude is condescending, demeaning, even including (p. 225) that “Kuhn had not studied the primary sources,” which is not true, an accusa- tion about which he might want to think twice. To the contrary, I believe The Copernican Revolution contains within its larger history, from antiquity to Newton, an account of the period from Copernicus to Galileo with a serious understanding of the astronomy and important issues, superior in compre- hension and clarity to what I have here, a fraction of the length, for good reason read to this day, and I strongly recommend reading it. In conclusion, it appears that Professor Westman’s history has problems or, as he may prefer, “problematics.” It stands, or falls, upon the assertion that Pico della Mirandola’s criticism of “a matter of crucial interest here: the order of the planets and the assignment of elemental qualities” in- spired Copernicus to rescue astrology from Pico’s criticism, to correct the uncertain order of the planets by inventing the heliocentric theory. But, as translation makes clear, Pico wrote not a word about “the order of the planets and the assignment of elemental qualities,” and neither did anyone else; it does not exist, and so could not inspire Copernicus, or anyone, to do anything. And where Pico does write about qualities of planets and the astrological signiªcance of order, Professor Westman is silent; nor does he know what Pico and Copernicus actually wrote about the order of the planets. This is the end of the astrological origin of the heliocentric theory, but is only the beginning, of hundreds of added pages on astronomy and astrology without astronomy and astrology, something that, as Galileo would say, “truly surpasses my imagination.” Beneath the appearance of erudition, the gravity of rumination, the plethora of citation, errors of fact

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and of understanding, of translation and of paraphrase, of commission and of omission, only touched upon here, are so innumerable that it could take as many pages as Professor Westman has written to explain and correct them. His word, his snippets of sources, cannot be taken on trust; it is necessary to read every original source to determine whether he is correct or incorrect, whether he has understood or read what he cites. No one but the author can be expected to do that, and it does not appear that he has done so or can do so. Trust once lost is difªcult to recover.

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