Abstract
Hayʾa or the study of the configuration of the universe grew out of the engagement of the scientists of Islam with the astronomy they had inherited from the Hellenistic world. One of the main projects of hayʾa was to arrive at a formulation of the cosmos in a manner that was consistent with the observed behavior of the heavenly bodies, as well as being in accord with the principals of physics as proposed by Aristotle. Its principal textual source was Ptolemy’s the Almagest (completed c. 175 CE), in which the celebrated Hellenistic astronomer formulated ingenious mathematical models through which he could predict the positions of the planets. These planetary motions were formulated as resulting from a combination of uniformly rotating circles suitably configured and linked in what has been described as a system of “wheels upon wheels.” The Almagest does not include Ptolemy’s concerns with the nature of his wheels, and the manner in which these wheels could correspond to physical reality. Indeed, regarding the planets (i.e., the Sun, the Moon, Mercury, Venus, Mars, Jupiter, and Saturn) the Almagest can be viewed as a collection of mathematical models aimed allowing astronomers to find the location of each planet at a given time. The physical reality of Ptolemy’s celestial wheels attracted a more substantial part of the author’s attention in a subsequent work, the Planetary Hypotheses. In Planetary Hypotheses, Ptolemy envisioned the cosmos as a set of nested shells; one brushing up against the next; and – adopting his models from the Almagest – embedded the machinery for each planet into its corresponding shell. This basic cosmological model was to prove remarkably long-lived. Indeed this concept – though reconfigured by Copernicus from geocentric to heliocentric – was to survive until the seventeenth century CE and the publication of Johannes Kepler’s Astronomica Nova. The system of nested shells formed the basic cosmological system of the hayʾa genre, itself one of the principle branches of astronomical research in the Islamic world. Though awe-inspiring and justly celebrated, this Ptolemaic system was not without issues. The most vexing of these issues to the scientists of hayʾa consisted of the need to reconcile the remarkable machinery of Ptolemy’s models to the philosophy of Aristotle. And in so far as the system proposed by Ptolemy deviated from the precepts of natural philosophy as described by Aristotle, a good deal of hayʾa research aimed at resolving the internal inconsistencies of this system.
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Notes
- 1.
Reconceptualized with great insistence to a system of “spheres within spheres” by Ṭūsī and other cosmographers of the Islamic tradition.
- 2.
Bernhard Goldstein, “The Arabic Version of Ptolemy’s Planetary Hypotheses,” Transactions of the American Philosophical Society, New Series 57, no. 4 (1967), 3–55.
- 3.
Paul Kunitzsch, “Almagest: Its Reception and Transmission in the Islamic World,” in Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures, ed. Helaine Selin (Dordrecht: Kluwer Academic, 1997), 55–6.
- 4.
Kunitzsch, “Almagest,” 56.
- 5.
Muḥammad ibn Aḥmad Bīrūnī, Kitāb al-qānūn al-masʿūdī (Ḥaydar Ābād al-Dakan: Maṭbaʿat Majlis Dāʾirat al-Maʿārif al-ʿUthmānīyah, 1954), vol. 1, 25; Goldstein, “The Arabic Version of Ptolemy’s Planetary Hypotheses,” 13.
- 6.
Kunitzsch, “Almagest,” 55.
- 7.
Fuat Sezgin, Geschichte des arabischen Schrifttums (Leiden: Brill, 1978), 6, 88–94.
- 8.
Sezgin, Geschichte des arabischen Schrifttums, 6, 92.
- 9.
One of the early copies of this work, Sipahsālār MS 592, is listed in Mudarris Razavi’s study. This work was completed in Marāgha and dates to October 1264, namely 20 years after the completion of the work; Muhammad Taqi Mudarris Razavi, Aḥwāl wa āthār-i Muḥammad Ibn Muḥammad Ibn al-Ḥasan al-Ṭūsī (Tehran: Intisharat-i Bunyad-i Farhang-i Iran, 1975), 348.
- 10.
Sezgin, Geschichte des arabischen Schrifttums, 93–4.
- 11.
B. A. Rozenfeld and Ekmeleddin Ihsanoğlu, Mathematicians, Astronomers and Other Scholars of Islamic Civilisation and Their Works (7th–19th C.) (Istanbul: Research Centre for Islamic History, Art, and Culture, 2003), 221.
- 12.
Rozenfeld and Ihsanoğlu, Mathematicians, Astronomers and Other Scholars, 238.
- 13.
Rozenfeld and Ihsanoğlu, Mathematicians, Astronomers and Other Scholars, 314.
- 14.
Rozenfeld and Ihsanoğlu, Mathematicians, Astronomers and Other Scholars, 434.
- 15.
Rozenfeld and Ihsanoğlu, Mathematicians, Astronomers and Other Scholars, 313.
- 16.
This work is itself the second volume of the three volume work Opera quae exstant omnia. The volume also includes Ptolemy’s treatise on fixed stars “Phaeis aplanon asteron.” Ptolemy, Opera quae exstant omnia II, (Leipzig: B.G. Teubner, 1907), 69–145.
- 17.
Goldstein, “The Arabic Version of Ptolemy’s Planetary Hypotheses,” 3; for a discussion of the research that remains to be done see G. J. Toomer’s review, “The Arabic Version of Ptolemy’s Planetary Hypotheses by Bernard R. Goldstein,” Journal of the American Oriental Society, 90, 2 (1970), 296–8.
- 18.
Goldstein, “The Arabic Version of Ptolemy’s Planetary Hypotheses,” 29.
- 19.
It is not difficult to see how Qur’anic verses such as “We will show them our portents on the horizons and within themselves in order for it to become apparent to them that it is the Truth (41:53)” could serve as impetus for the need to study the natural world. See Seyyed Hossein Nasr, An Introduction to Islamic Cosmological Doctrines: Conceptions of Nature and Methods Used for its Study by the Ikhwān al-Ṣafāʾ, al-Bīrūnī, and Ibn Sīnā, (Albany: State University of New York Press, 1993), 6–11.
- 20.
Bīrūnī writes in the introduction to his Kitāb al-qānūn al-masʿūdī: “The views [regarding this topic] are as varied as suppositions regarding it are plentiful. And this is not the place to examine the contradictions of the uncertainties nor to isolate that which is true from the doubts which sully it. And the principles of this art, though essential [by virtue of their reliance on geometric proofs], have not been organized in the well-known books [in a manner to allow] for confidence to be strengthened by them, and for it to be possible to point to them and to rely on them. [And this fault is true] even of the Almagest which is the manual for this art, the author of which being the leader of its practitioners.” Bīrūnī, al-Qānūn.
- 21.
George Saliba, “Aristotelian Cosmology and Arabic Astronomy,” in De Zénon d’Elée à Poincaré: Recueil d’Études en Hommage à Roshdi Rashed, ed. Régis Morelong and Ahmad Hasnawi (Louvain: Peeters, 2004), 251–268.
- 22.
Saliba, “Aristotlian Cosmology,” 252–3.
- 23.
Saliba, “Aristotlian Cosmology,” 256–7.
- 24.
George Saliba, Islamic Science and the Making of the European Renaissance (Cambridge: MIT Press, 2007), 97–106.
- 25.
al-Ḥasan Abū ʿAlī Ibn al-Haytham, al-Shukūk ʿalā Baṭlamyūs, ed. A. I. Sabra, and Nabīl Shihābī (Cairo: Maṭbaʿat Dār al-Kutub, 1971), 23.
- 26.
Ibn al-Haytham, al-Shukūk, 15.
- 27.
Ibn al-Haytham, al-Shukūk, 34.
- 28.
Ibn al-Haytham, al-Shukūk, 44.
- 29.
Ibn al-Haytham, al-Shukūk, 47–59; Saliba, Islamic Science, 105; Don L. Voss, “Ibn Al-Haytham’s Doubts Concerning Ptolemy: A Translation and Commentary,” (PhD diss., University of Chicago, 1985).
- 30.
Saliba, “Aristotelian Cosmology,” 260–3.
- 31.
Saliba, “Aristotelian Cosmology,” 263–7.
- 32.
“The science of astronomy of our times contains nothing existent, rather, the astronomy of our time conforms only to computation, and not to existence.” Quoted in Saliba, “Aristotelian Cosmology,” 258.
- 33.
Saliba, Islamic Science, 95.
- 34.
F. J. 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. Charles Burnett et al. (Leiden; Boston: Brill, 2004), 787.
- 35.
Saliba, Islamic Science, 120–1.
- 36.
George Saliba, The Astronomical works of Muʾayyad al-Dīn al-ʿUrḍī: A Thirteenth Century Reform of Ptolemaic Astronomy,ʿUrḍī’s Kitāb al-hayʾa (Beirut: Markaz dirāsāt al-waḥda al-ʿArabīya, 1995), 49–59.
- 37.
George Saliba, “Arabic Planetary Theories after the Eleventh Century AD,” in Encyclopedia of the History of Arabic Sciences, ed. Roshdi Rashed. (London: Routledge, 1996), 95–9. See also Kaveh Niazi, Quṭb al-Dīn Shīrāzī and the Configuration of the Heavens: A Comparison of Texts and Models (Dordrecht: Springer, 2014), 101–20.
- 38.
A successor of al-ʿUrḍī, Shīrāzī, and Ṭūsī, the celebrated Syrian astronomer ʿAlaʾ al-Dīn ʿAlī ibn al-Shāṭir (d. 1372 CE) represents the culmination of non-Ptolemaic hay’a research in the Islamic world. See Saliba, “Arabic Planetary Theories,” 120–122. See also E. S. Kennedy and Victor Roberts, “The Planetary Theory of Ibn al-Shāṭir,” ed. E. S. Kennedy and Imad Ghanem (Aleppo: Aleppo University Publications, 1976), 60–68.
- 39.
See Ṭūsī’s remarks near the end of his discussion for the Moon, Book Two, Chapter Five.
- 40.
The relative chronology of these works will be discussed in the following chapter.
- 41.
Ragep, F. J., Tadhkira, 216; Saliba, George, “The Role of the Almagest Commentaries in Medieval Arabic Astronomy, A Preliminary Survey of Ṭūsī’s Redaction of Ptolemy’s Almagest,” Archives Internationales d’Histoires Des Sciences 37 (1987): 3–20; George Saliba and E. S. Kennedy, “The Spherical Case of the Ṭūsī Couple,” Arabic Sciences and Philosophy 1, no. 2 (1991): 285–291.
- 42.
Saliba, “Aristotelian Cosmology,” 263–267.
- 43.
See Book Two, Chapter Five.
- 44.
Ṭūsī’s patrons in the Ismāʿīlī forts of Quhistān and Daylamān would have had at their disposal impressive libraries. In their patronage of culture and science the Ismā’īlīs were following the lead of their Fatimid predecessors. Farhad Daftary, “Introduction: Ismaʿilis and Ismaʿili Studies,” in Mediaeval Ismaʿili History and Thought, ed. Farhad Daftary (New York: Cambridge University Press, 1996), 3. It should be noted here that the practice of omitting geometrical proofs was by no means universal. This can be seen, for instance, in the hayʾa works of Athīr al-Dīn Abharī, many of which are replete with geometrical proofs.
- 45.
Ṭūsī, <Emphasis Type="Italic">Zubdat al-idrāk fī hayʾat al-aflāk,, ed. ʿAbbās Sulaymān (Alexandria: Dār al-maʿrifat al-jāmiʿīya, 1994), 45.
- 46.
I have so far not encountered Ṭūsī’s remarkable phrasing in the works of the hayʾa astronomers preceding him. A virtually identical formulation occurs in Shīrāzī’s Ikhtiyārāt-i muẓaffarī, however, as discussed below. I am grateful to Ben Kavoussi and his insights regarding the Hermetic influences in the works of Shīrāzī’s contemporary, Rashīd al-Dīn Ṭabīb.
- 47.
As noted earlier, one of the chapters of the Ḥall has been published; Ragep, F. J., “Ibn al-Haytham and Eudoxus,” 786–809. Furthermore, a new edition of Risāla-yi muʿīnīya and the Ḥall was published recently: Nik-fahm, Sajjad, and Fatemeh Savadi, Al-Risāla al-muʿīnīyya wa ḥall mushkilāt muʿīnīyya, (Tehran: Mirath-i Maktub, 2020).
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Niazi, K. (2022). Ṭūsī’s Hayʾa. In: A Princely Pandect on Astronomy. Archimedes, vol 58. Springer, Cham. https://doi.org/10.1007/978-3-030-50761-9_1
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