Copernicus and His Islamic Predecessors: Some Historical Remarks

Kennedy noticed non-Ptolemaic astronomical models in Ibn al-Shatir's Nihayat al-sul.

“E. S. Kennedy, who was a professor of mathematics at the American University of Beirut, happened by chance to notice some unusual (i.e.non-Ptolemaic) astronomical models while browsing through the Nihayat alsul of c Ala' al-Din Ibn al-Shatir”

• cites [3] 3. Dreyer knew of Tusi's work from the translation by Carra de Vaux of a chapter of his al-Tadhkira fi c ilm al-hay'a ("Les sphères célestes selon Nasir Eddin-Attusi" in Paul Tannery, Recherches sur l'histoire de l'astronomie ancienne (Paris, 1893), Appendix VI, pp. 337-61).Not matched

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The latest Islamic author cited by Copernicus, al-Bitruji, flourished in Spain in the last part of the twelfth century.

“The latest of these authors, al-Bitruji, flourished in Spain in the last part of the twelfth century”

• cites [1] 1. These are: al-Battani, al-Bitruji, al-Zarqallu, Ibn Rushd, and Thabit ibn Qurra. Copernicus also refers to al-Battani in his Commentariolus, which remained unpublished during his lifetime. "Islamic" here refers to the civilization of Islam, not the religion, since a number of "Islamic" astronomers, such as Thabit, were not Muslims.Not matched

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The models Kennedy found in Ibn al-Shatir were ones previously thought to have first appeared in Copernicus.

“Kennedy was amazed to learn that these models were ones that had been thought to have first appeared in the works of Nicholas Copernicus.”

• cites [3] 3. Dreyer knew of Tusi's work from the translation by Carra de Vaux of a chapter of his al-Tadhkira fi c ilm al-hay'a ("Les sphères célestes selon Nasir Eddin-Attusi" in Paul Tannery, Recherches sur l'histoire de l'astronomie ancienne (Paris, 1893), Appendix VI, pp. 337-61).Not matched

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Earlier European astronomers seem not to have made the objection to Ptolemy's equant.

“but which seems not to have been made by earlier European astronomers).14”

• cites [14] 14. We should note, though, that recently Michał Kokowski, in defending Copernicus's originality, has also conceded that the Islamic models are also somehow revolutionary according to his "correspondence principle" inasmuch as they supersede those of Ptolemy by overcoming the problematic equant (Copernicus's originality: Towards integration of contemporary Copernican studies (Warsaw, 2004), 75-77). Here he follows George Saliba, who maintained that the Maragha school astronomers were revolutionary because of their "realization that astronomy ought to describe the behaviour of physical bodies iNot checked — no full text of the source

Tusi's models seem to have been widely known by contemporaries of Copernicus, including Giovanni Battista Amico and Girolamo Fracastoro.

“It is also noteworthy that Tusi's models seem to have been widely known by contemporaries of Copernicus; examples include Giovanni Battista Amico and Girolamo Fracastoro.19”

• cites [19] 19. Di Bono, op. cit. (ref. 19), 153-4.Not matched

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Copernicus explicitly cited five Islamic authors in De revolutionibus.

“Copernicus in De revolutionibus explicitly cited five Islamic authors. 1”

• cites [1] 1. These are: al-Battani, al-Bitruji, al-Zarqallu, Ibn Rushd, and Thabit ibn Qurra. Copernicus also refers to al-Battani in his Commentariolus, which remained unpublished during his lifetime. "Islamic" here refers to the civilization of Islam, not the religion, since a number of "Islamic" astronomers, such as Thabit, were not Muslims.Not matched

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Copernicus objected explicitly to Ptolemy's use of the equant.

“In particular Copernicus objected explicitly to Ptolemy's use of the equant”

• cites [14] 14. We should note, though, that recently Michał Kokowski, in defending Copernicus's originality, has also conceded that the Islamic models are also somehow revolutionary according to his "correspondence principle" inasmuch as they supersede those of Ptolemy by overcoming the problematic equant (Copernicus's originality: Towards integration of contemporary Copernican studies (Warsaw, 2004), 75-77). Here he follows George Saliba, who maintained that the Maragha school astronomers were revolutionary because of their "realization that astronomy ought to describe the behaviour of physical bodies iNot checked — no full text of the source

Dreyer in 1906 first acknowledged a connection between Copernicus and a post-1200 Islamic astronomer.

“The first modern acknowledgement of a connection between Copernicus and a later (i.e.post-1200) Islamic astronomer was made by J. L. E. Dreyer in 1906.”

• cites [2] 2. J. L. E. Dreyer, History of the planetary systems from Thales to Kepler (Cambridge, 1906), 269.Not matched

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Since the 1950s, discoveries have caused a major re-evaluation of the relation of Copernicus and other Renaissance astronomers to later Islamic astronomy.

“since the 1950s, a series of discoveries has shaken this neatly constricted picture and caused a major re-evaluation of the relation of Copernicus (as well as other Renaissance astronomers) to later Islamic astronomy.”

Copernicus was compelled to adopt a heliocentric system with the Earth as a planet moving around the Sun.

“Thus Copernicus was compelled to opt for a heliocentric system with the Earth, as a planet, in motion around the Sun.15”

• cites [15] 15. Recent books by two mediaevalists, A. C. Crombie and Edward Grant, advocate the European nature of modern science, thus reverting to the more traditional viewpoint. See Crombie's Styles of scientific thinking in the European tradition: The history of argument and explanation especially in the mathematical and biomedical sciences and arts (London, 1994), and Grant's The foundations of modern science in the Middle Ages: Their religious, institutional, and intellectual contexts (Cambridge, 1996) and idem, God and reason in the Middle Ages (Cambridge, 2001). This view is held by both Western aNot matched

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Even those who hold to a notion of scientific revolution have focused on local European contexts and consequences rather than origins of Copernicanism.

“even those who still hold to some notion of a scientific revolution have tended to focus their attention on local contexts (usually European) for explanations and to look at the consequences rather than the origins of Copernicanism.22”

• cites [22] 22. For this Spanish episode in Islamic astronomy, see Sabra, op. cit. (ref. 8), 133-53.Not matched

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Objection to the equant had been a staple of Islamic astronomy for about five centuries by Copernicus's time.

“an objection that had been a staple of Islamic astronomy for some five centuries at that point”

• cites [14] 14. We should note, though, that recently Michał Kokowski, in defending Copernicus's originality, has also conceded that the Islamic models are also somehow revolutionary according to his "correspondence principle" inasmuch as they supersede those of Ptolemy by overcoming the problematic equant (Copernicus's originality: Towards integration of contemporary Copernican studies (Warsaw, 2004), 75-77). Here he follows George Saliba, who maintained that the Maragha school astronomers were revolutionary because of their "realization that astronomy ought to describe the behaviour of physical bodies iNot checked — no full text of the source

Beginning in the first half of the thirteenth century, a number of works in the Islamic East proposed alternatives to Ptolemy's planetary models.

“Beginning in the first half of the thirteenth century, a number of works appeared that proposed alternatives to Ptolemy's planetary models.”

• cites [10] 10. Nicholas Copernicus, De revolutionibus orbium coelestium, transl. by E. Rosen as On the revolutions (Baltimore, 1978), 18.Not matched

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Ptolemy used devices that violated physical principles accepted by most ancient and medieval astronomers.

“One particular irritant was the use of devices by Ptolemy that violated the accepted physical principles that had been adopted by most astronomers in the ancient and medieval periods.”

• cites [4] 4. These have been conveniently collected in E. S. Kennedy and Imad Ghanem (eds), The life & work of Ibn al-Shatir: An Arab astronomer of the fourteenth century (Aleppo, 1976), and in E. S. Kennedy et al., Studies in the Islamic exact sciences (Beirut, 1983), 50-107. The most important of these is E. S. Kennedy, "Late medieval planetary theory", Isis, lvii (1966), 84-97.Not matched

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The earliest systematic Islamic critique of Ptolemy's methods and devices was Ibn al-Haytham's Doubts against Ptolemy.

“The earliest systematic attempt in Islam to criticize Ptolemy's methods and devices occurred in al-Shukuk c ala Batlamyus (Doubts against Ptolemy) by Ibn al-Haytham (d.c. 1040)”

• cites [5] 5. See, for example, the very critical remarks, most likely by the Banu Musa (ninth century), in Régis Morelon, Thabit ibn Qurra: Œuvres d'astronomie (Paris, 1987), 61.Not matched

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Abu Ubayd al-Juzjani proposed a model to deal with the equant problem.

“Abu c Ubayd al-Juzjani, who was an associate of Abu c Ali Ibn Sina (= Avicenna, d. 1037), also dealt with these issues and proposed a model to deal with the equant problem.7”

• cites [7] 7. F. Jamil Ragep, "Ibn al-Haytham and Eudoxus: The revival of homocentric modeling in Islam", in Studies in the history of the exact sciences in honour of David Pingree, ed. by C. Burnett et al. (Leiden, 2004), 786-809. sourceNot checked — no full text of the source

These astronomers developed mathematical tools such as the Tusi couple and the Urdi lemma that allowed connected circular motions to reproduce approximately the effects of devices such as Ptolemy's equant.

“these astronomers developed mathematical tools (such as the”

• cites [11] 11. Good overviews can be found in George Saliba, "The astronomical tradition of Maragha: A historical survey and prospects for future research", Arabic science and philosophy, i (1991), 67-99 (reprinted in idem, History (ref. 7), 258-90), and George Saliba, "Arabic planetary theories after the eleventh century AD", in Encyclopedia of the history of Arabic science, ed. by R. Rashed (3 vols, London, 1996), i, 58-127. sourceNot checked — no full text of the source

Islamic authors from an early period criticized Ptolemy's methods, observations, and models.

“Islamic authors from an early period were critical of Ptolemy's methods, observations, and models.4”

• cites [4] 4. These have been conveniently collected in E. S. Kennedy and Imad Ghanem (eds), The life & work of Ibn al-Shatir: An Arab astronomer of the fourteenth century (Aleppo, 1976), and in E. S. Kennedy et al., Studies in the Islamic exact sciences (Beirut, 1983), 50-107. The most important of these is E. S. Kennedy, "Late medieval planetary theory", Isis, lvii (1966), 84-97.Not matched

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Among the most important new alternative models were those of Nasir al-Din al-Tusi, Mu'ayyad al-Din al-Urdi, Qutb al-Din al-Shirazi, Ala' al-Din Ibn al-Shatir, and Shams al-Din al-Khafri.

“Among the most important of these new models were those of Nasir al-Din al-Tusi (1201-74), Mu'ayyad al-Din al-c Urdi (d.c. 1266), Qutb al-Din al-Shirazi (1236-1311), c Ala' al-Din Ibn al-Shatir (d.c. 1375), and Shams al-Din al-Khafri (fl.1525).10”

• cites [10] 10. Nicholas Copernicus, De revolutionibus orbium coelestium, transl. by E. Rosen as On the revolutions (Baltimore, 1978), 18.Not matched

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Ibn al-Haytham wrote a treatise attempting to address problems in Ptolemy's planetary latitude models.

“Ibn al-Haytham also wrote a treatise in which he attempted to deal with some of the problems of Ptolemy's planetary latitude models.6”

• cites [6] 6. F. J. Ragep, Nasir al-Din al-Tusi's memoir on astronomy (2 vols, New York, 1993), i, 48-51. sourceNot checked — no full text of the source

The Spanish revolt against Ptolemy was episodic rather than the beginning of a long-lived tradition of Islamic homocentric astronomy.

“the Spanish”

The presence of MS Vat.Gr. 211 in the Vatican, perhaps in the fifteenth century, provides a possible means for transmission of knowledge of Tusi's models.

“The fact that this manuscript found its way to the Vatican, perhaps in the fifteenth century, provides a possible means for the transmission of knowledge of Tusi's models.”

In the rectilinear Tusi couple, two spheres, one half the size and internally tangent to the other, rotate in opposite directions with the smaller twice as fast as the larger, causing a point on a diameter of the larger sphere to oscillate rectilinearly.

“In the case of the rectilinear Tusi couple, two spheres, one half the size and internally tangent to the other, rotate in opposite directions with the smaller twice as fast as the larger.The result of these motions is that a given point on a diameter of the larger sphere will oscillate rectilinearly.”

• cites [11] 11. Good overviews can be found in George Saliba, "The astronomical tradition of Maragha: A historical survey and prospects for future research", Arabic science and philosophy, i (1991), 67-99 (reprinted in idem, History (ref. 7), 258-90), and George Saliba, "Arabic planetary theories after the eleventh century AD", in Encyclopedia of the history of Arabic science, ed. by R. Rashed (3 vols, London, 1996), i, 58-127. sourceNot checked — no full text of the source

Ptolemy in the Almagest placed mathematics above natural philosophy and metaphysics.

“In the introduction to the Almagest, Ptolemy reverses the order of the sciences and places mathematics above natural philosophy and metaphysics (or”

• cites [34] 34. See Menso Folkerts, "Regiomontanus' role in the transmission and transformation of Greek mathematics", in Tradition, transmission, transformation: Proceedings of two conferences on premodern science held at the University of Oklahoma, ed.Not matched

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The author has published a treatise by Ali Qushji that presents and proves a proposition found in Book XII of Regiomontanus's Epitome of the Almagest, completed in 1463.

“I have published a small treatise by c Ali Qushji (d.1474) that presents and proves a proposition that appears in Book XII of Regiomontanus's Epitome of the Almagest, which was completed in 1463.44”

• cites [44]Not matched

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Academic boundaries have made dialogue between medieval Latinists, Islamists, and early modernists difficult.

“Because historians of science specializing in Islamic civilization have tended to be marginalized, in part for disciplinary reasons, in part because of the arcane nature of many of their publications, it has been surprisingly difficult to initiate an on-going dialogue between medieval Latinists, Islamists, and early modernists.26”

• cites [26] 26. Morris R. Cohen and I. E. Drabkin, A source book in Greek science (Cambridge MA, 1948), 90-91.Not matched

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Tusi did not believe the astronomer could be completely independent of natural philosophers and metaphysicians.

“But Tusi for one did not believe that this meant that the astronomer could be completely independent of the natural philosophers and metaphysicians, since there were certain principles that only the natural philosophers could provide the astronomer.”

The chance of a link to Regiomontanus is increased by the absence of context or justification when Regiomontanus presented the proposition, in contrast to Qushji's extensive treatment of his own discovery and his explanation of why Ptolemy forbade such a conversion for Mercury and Venus.

“In that article, I argue that the possibility of a connection to Regiomontanus was strengthened by the lack of a context or justification in which Regiomontanus presented the proposition, which stands in stark contrast to the expansive manner in which Qushji discusses his own discovery (as a result of dealing with the Mercury model) and his attempt to explain why Ptolemy disallowed such a tran”

• AssumptionRests on an assumption: The absence of contextual justification in Regiomontanus's presentation of a proposition indicates that he did not originate it independently.

Regiomontanus and his successors reflect the mathematical humanism that flourished briefly in Central Asia.

“In short, Regiomontanus, and his successors, reflect the mathematical humanism that had a brilliant but short life in Central Asia.52”

• cites [52]Not matched

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• AssumptionThe authors state this as an assumption: The mechanism of transmission need not be identified for products to provide evidence of borrowing.

Before Copernicus, the European tradition contained almost nothing comparable to this new conception.

“But there is hardly anything like this in the European tradition before Copernicus.43”

• cites [43]Not matched

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Most Islamic astronomers followed the Geminus formulation, elaborating it using the quia/propter quid distinction.

“Most Islamic astronomers followed this formulation, elaborating and clarifying it using the fact/reasoned fact (quia/propter quid) distinction of Aristotle's Posterior analytics.”

• cites [35] 35. by F. J. Ragep and S. P. Ragep (Leiden, 1996), 89-113.Not checked — no full text of the source
• cites [36] 36. James Steven Byrne, "A humanist history of mathematics? Regiomontanus's Padua Oration in context", Journal of the history of ideas, lxvii (2006), 41-61, p. 61. sourceNot checked — no full text of the source

The strong resemblance between Qushji's figure and Regiomontanus's figure increases the likelihood that transmission occurred.

“The striking similarity of Qushji's figure that accompanies his text and that of Regiomontanus (Figure 1) adds to the possibility that this is a matter of transmission.”

• AssumptionRests on an assumption: Textual and figural similarities between works are evidence of transmission or influence rather than independent parallel development.

Tusi presented the uniformity of celestial motion in a way that did not depend on its ultimate cause.

“Nasir al-Din al-Tusi, for example, presented the critical principle of the uniformity of celestial motion in such a way that it did not depend upon the ultimate cause.”

• cites [38] 38. See above, ref. 18 (on the transmission of Islamic astronomy to Byzantium). And as Otto Neugebauer has remarked: "There is no reason to assume that there is any period in which Islamic astronomy was not known in Constantinople" (A history of ancient mathematical astronomy (3 parts, New York, 1975), i, 11). Cf. Maria Mavroudi, A Byzantine book on dream interpretation: The Oneirocriticon of Achmet and its Arabic sources (Leiden, 2002); Alain Touwaide, "Arabic urology in Byzantium", Journal of nephrology, xvii (2004), 583-9; and Alain Touwaide, "Arabic medicine in Greek translation: A prelimiNot checked yet

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Neither among the Paduans nor among European astronomers before Copernicus is there criticism of the equant or other Ptolemaic devices violating uniform circular motion.

“It is also important to note that neither among the Paduans nor among European astronomers and natural philosophers before Copernicus is there a criticism of the equant or other Ptolemaic devices that lead to a violation of uniform, circular motion.33”

• cites [33] 33. F. Jamil Ragep, " c Ali Qushji and Regiomontanus: Eccentric transformations and Copernican revolutions", Journal for the history of astronomy, xxxvi (2005), 359-71. sourceNot checked — no full text of the source

Qushji rejected Ptolemy's view that an observational test of the Earth's rest was possible.

“Starting with his view that the astronomer should not depend on the natural philosopher, but also rejecting Ptolemy's view that an observational test was possible, Qushji made the remarkable claim that nothing false follows from the assumption of a rotating Earth.41”

• cites [41] 41. A very important article that takes up the mathematical humanism of Samarqand is Ihsan Fazlıo¢lu's "Osmanlı felsefe-biliminin arkaplanı: Semerkand matematik-astronomi okulu", Dîvân ilmî araºtırmalar, xiv/1 (2003), 1-66. A revised version in English will appear in a forthcoming issue of the Journal for the history of Arabic science.Not matched

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The Andalusian revolt's extreme position against Ptolemy's epicycles and eccentrics led to a failed project with virtually no impact on the Eastern hay'a tradition.

“What we know from the Andalusian revolt is that its extreme position against Ptolemy's epicycles and eccentrics led to a failed project that had virtually no impact on the Eastern hay'a tradition.”

• cites [32] 32. A discussion of this Islamic discourse on the Earth's possible rotation is in F. Jamil Ragep, "Tusi and Copernicus: The Earth's motion in context", Science in context, xiv (2001), 145-63. 41. Ibid., 157. 42. Ibid., 145-8.Not matched

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Under the influence of Islamic theologians, physical principles in astronomical texts shifted.

“Most likely under the influence of Islamic theologians, who were fundamentally opposed to Aristotelian notions of natural cause, we can see subtle shifts in how physical principles were presented in the introductory parts of astronomical texts.37”

• cites [37] 37. Michael H. Shank, "The classical scientific tradition in fifteenth-century Vienna", in F. J. Ragep and S. P. Ragep (eds), Tradition, transmission, transformation (ref. 45), 115-36, p. 131. 48. Ibid., 126.Not matched

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Qushji claimed that assuming a rotating Earth leads to no false consequence.

“Starting with his view that the astronomer should not depend on the natural philosopher, but also rejecting Ptolemy's view that an observational test was possible, Qushji made the remarkable claim that nothing false follows from the assumption of a rotating Earth.41”

• cites [41] 41. A very important article that takes up the mathematical humanism of Samarqand is Ihsan Fazlıo¢lu's "Osmanlı felsefe-biliminin arkaplanı: Semerkand matematik-astronomi okulu", Dîvân ilmî araºtırmalar, xiv/1 (2003), 1-66. A revised version in English will appear in a forthcoming issue of the Journal for the history of Arabic science.Not matched

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That transmission would have involved the idea that astronomy could and should rest on new physical principles that are mathematically and empirically grounded, not on Aristotelian natural philosophy.

“In this case, that transmission would have consisted of the notion that astronomy could, indeed should, be based upon a new set of physical principles that would be mathematically and empirically based, rather than upon Aristotelian natural philosophy.”

The long and vigorous Islamic discussion of this issue, linked to the Earth's movement, indicates that a conceptual foundation for borrowing existed.

“The fact that we can find a long, vigorous discussion in Islam of this issue intricately-tied to the question of the Earth's movement should indicate that such a conceptual foundation was there for the borrowing.”

• AssumptionThe authors state this as an assumption: The mechanism of transmission need not be identified for products to provide evidence of borrowing.

One must distinguish general criticism of Ptolemy's eccentrics and epicycles from the tradition of criticism of irregular motions initiated by Ibn al-Haytham, which includes Copernicus.

“One must be careful to distinguish a general criticism of Ptolemy's eccentrics and epicycles (and an advocacy of homocentric astronomy) from the tradition of criticism of Ptolemy's irregular motions that was initiated by Ibn al-Haytham, a tradition that clearly includes Copernicus.”

A three-century debate followed Tusi in which authors disputed whether Tusi or Ptolemy was right about whether observation could prove the Earth's rest.

“After Tusi, we can trace a three-century discussion in which various authors argued whether he or Ptolemy was correct regarding the possibility of an observational proof of the Earth's state of rest.”

Copernicus placed himself within the tradition of Islamic criticisms of Ptolemy's violations of uniform circular motions.

“Copernicus puts himself squarely within the tradition of Islamic criticisms of Ptolemy's violations of uniform, circular motions in the heavens.”

This tradition lasted for some six centuries with vigorous discourse and proposals.

“Furthermore this tradition lasted for some six centuries in which there was a very vigorous discourse that led to various proposals, criticisms, and counter-proposals by an active group of astronomers from many regions of the Islamic world.”

What lacked a counterpart until the late fifteenth century was the interaction of these elements with the advanced astronomical tradition that had developed over centuries in the Islamic world.

“What did not have a counterpart until the late fifteenth century was their interaction with the advanced astronomical tradition that had developed over many centuries within the Islamic world.”

Ptolemy, in Almagest I.7, held that observation could establish that the Earth is stationary.

“This was contrary to Ptolemy's position in the Almagest (I.7), namely that one could establish a static Earth through observation.”

• cites Almagest (I.7)Not matched

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In the Islamic world, the revolutionary rejection of Aristotelian physics in astronomy took hundreds of years, many scholars, and thousands of pages before it culminated in Ali Qushji in Samarqand.

“In the Islamic world, the revolutionary rejection of Aristotelian physics in astronomy was something that took hundreds of years, dozens of scholars, and thousands of pages before it bore fruit in the person of c Ali Qushji in Samarqand.”

That proposition permits the conversion of all Ptolemy's planetary epicyclic models into eccentric models.

“The importance of this proposition can scarcely be overstated, since it allows one to transform all of Ptolemy's planetary epicyclic models into eccentric models”

• cites [44]Not matched

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