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Published online by Cambridge University Press:  12 August 2011

Damien Janos*
Courant Research Centre EDRIS, Georg-August-UniversitätNikolausberger Weg 23 37073 Göttingen


Ibn Sīnā's celestial kinematics represents an important aspect of his cosmology but has up to now received little attention in the secondary literature. After a short overview of some key features of his cosmology, this article attempts to clarify the role played by the separate intellects, the celestial souls, and the celestial bodies in causing celestial motion. It challenges the common view that Ibn Sīnā adhered to the theory of ten separate intellects developed by al-Fārābī and attempts to reconstruct his astronomical-metaphysical model on the basis of his main philosophical works. In addition, the article addresses the thorny question of how motion is transmitted from the intellectual to the physical plane, and it sheds light on the place of physics, metaphysics, and astronomy in Ibn Sīnā's cosmological method.


La théorie avicenienne du mouvement des orbes célestes représente un aspect important de sa cosmologie qui n'a cependant pas encore été l'objet d'une étude approfondie. Cet article compte combler ce manque en fournissant une analyse des différents principes à l'origine du mouvement céleste, ainsi qu'une réflexion sur le rôle des disciplines astronomique, physique, et métaphysique dans les explications que fournit Ibn Sīnā à ce sujet. L'accent est mis sur le rapport des intelligences aux orbes et sur la problématique du passage de l'intellectif au physique, un moment charnière dans la cinématique avicenienne. En outre, l'étude remet en question l'adhésion d'Ibn Sīnā à la théorie farabienne des dix intelligences et entreprend une reconstitution de son modèle cosmologique.

Research Article
Copyright © Cambridge University Press 2011

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1 Ibn Sīnā's cosmology and metaphysics have already been widely studied, but scholars have focused primarily on his theories of causality and emanation. In what follows, I cite only the works that are most relevant to the present topic: Goichon, A.-M., La distinction de l'essence et de l'existence d'après Ibn Sīnā (Paris, 1935)Google Scholar; Nasr, S. H., An Introduction to Islamic Cosmological Doctrines: Conceptions of Nature and Methods Used for its Study by the Ikhwān al-Ṣafā', al-Bīrūnī, and Ibn Sīnā (London, 1978)Google Scholar; Davidson, H. A., Alfarabi, Avicenna, and Averroes on Intellect: Their Cosmologies, Theories of the Active Intellect, and Theories of Human Intellect (New York/Oxford, 1992)Google Scholar; Netton, I. R., Allāh Transcendent: Studies in the Structure and Semiotics of Islamic Philosophy, Theology, and Cosmology (London, 1989)Google Scholar; Maróth, M., Die Araber und die antike Wissenschaftstheorie (Leiden/New York/Köln, 1994)Google Scholar, and id., “The ten intellects cosmology and its origin,” The Arabist, 13-14 (1995): 103–13; Wisnovsky, R., Avicenna's Metaphysics in Context (Ithaca, N.Y, 2003)Google Scholar; id., Final and efficient causality in Avicenna's cosmology and theology,” Quaestio, 2 (2002): 97123CrossRefGoogle Scholar; id., “Towards a history of Avicenna's distinction between immanent and transcendent causes,” in Reisman, D. and Al-Rahim, A. H. (eds.), Before and After Avicenna (Leiden, 2003), pp. 4968Google Scholar. In addition, see McGinnis, J., “Positioning heaven: the infidelity of a faithful Aristotelian,” Phronesis, 51/2 (2006): 140–61CrossRefGoogle Scholar, for a specific study of a physical problem in Ibn Sīnā' cosmology, as well as Y. Michot's edition and analysis of Ibn Sīnā's Réfutation de l'astrologie (Beirut, 2006)Google Scholar, for insight into Ibn Sīnā's attitude toward astrology. In spite of their value, none of these contributions provides a detailed analysis of Ibn Sīnā's views on celestial motion.

2 I have used the following editions: Ibn Sīnā, Al-Shifāʾ, taṣdīr Ṭāhā Ḥusayn; murājaʿat Ibrāhīm Madkūr; taḥqīq, al-Ab Qanawātī, Maḥmūd al-Khuḍayrī, Fuʾād al-Ahwānī, 4 vols. (Qum, 1404-1406/1983 or 1984-1985 or 1986); id., The Metaphysics of The Healing: A Parallel English-Arabic Text, translated, introduced, and annotated by Marmura, M. E. (Provo, UT, 2005)Google Scholar; id., al-Najāt min al-gharaq fī baḥr al-ḍalālāt, edited by M. T. Dānishpazūh (Tehran, 1364/1985-86); id., al-Ishārāt wa-al-tanbīhāt, maʿa sharḥ Naṣīr al-Dīn al-Ṭūsī, 4 vols., edited by S. Dunyā (Egypt, 1957-60); id., al-Mabdaʾ wa-al-maʿād, edited by Nūrānī, A. (Tehran, 1984)Google Scholar. With regard to Shifāʾ, and in addition to the Metaphysics or Ilāhiyyāt section, I will be referring particularly to Ibn Sīnā's al-Samāʾ wa-al-ʿālam (henceforth Samāʾ) contained in the Physics section, as well as to his commentary on Ptolemy's Almagest, Taḥrīr Kitāb al-Majisṭī (henceforth Taḥrīr al-Majisṭī), contained in the Mathematics section.

3 For Ibn Sīnā's study of the Ptolemaic texts and where this Greek source fits in his educational curriculum, see Gutas, D., Avicenna and the Aristotelian Tradition (Leiden, 1988), pp. 149–54Google Scholar. For the Almagest, see Ptolemy's Almagest, translated and annotated by G. J. Toomer (London, 1984); P. Kunitzsch, Der Almagest: die Syntaxis mathematica des Claudius Ptolemäus in arab.-lat. Überlieferung (Wiesbaden, 1974). For the Planetary Hypotheses, see Goldstein, B., “The Arabic version of Ptolemy's Planetary Hypotheses,” Transactions of the American Philosophical Society, new series, 57/4 (1967): 355CrossRefGoogle Scholar. Book One of Ptolemy's Planetary Hypotheses was edited and translated into French by Morelon, R.: “Le traité I du Livre des Hypothèses de Ptolémée,” MIDEO, 21 (1993): 787Google Scholar. A recent analysis of the Greek to Arabic transmission and translation processes with respect to Ptolemy's works is given by Saliba, G., Islamic Science and the Making of the European Renaissance (Cambridge, Mass., 2007)Google Scholar, especially Chapters 1 and 3. Saliba argues for an earlier date for the transmission and assimilation of Ptolemaic astronomy in Islam than the one usually mentioned in surveys of Islamic science, shifting its beginning from the time of al-Maʾmūn to the time of al-Manṣūr and even earlier to the Umayyad period. The question of whether Ibn Sīnā knew Planetary Hypotheses, in addition to Almagest, upon which he wrote a commentary, is still unclear, since he does not mention this text by name. Yet as the present article will show, many theories discussed by Ibn Sīnā seem to stem from this important work, which would argue for a positive answer to this question.

4 A salient example is the highly influential didactic treatise written by Aḥmad ibn Muḥammad ibn Kathīr al-Farghānī, Jawāmiʿ ʿilm al-nujūm wa-uṣūl al-ḥarakāt al-samāwiyya, edited and translated by Jacob Golius (Frankfurt am Main, 1986 [1669]).

5 As Hübner, W., “The Ptolemaic view of the universe,” Greek, Roman, and Byzantine Studies, 41/1 (2000): 5993Google Scholar, 64–5, notes, this planetary arrangement, which is usually called ‘Ptolemaic’ and which became the main astronomical paradigm in late-antiquity, can nevertheless be traced back as far as the third century BCE.

6 Doubts on this issue are raised in Mabdaʾ, p. 68, and especially in Samāʾ, p. 46,5–7. Ibn Sīnā in these passages does not give any reasons for his doubting, but a potential factor could have been the varying degrees of brightness of the stars.

7 Ibn Sīnā, The Metaphysics of the Healing, pp. 328,28; 331,8; and Michot's remarks in id., Réfutation de l'astrologie, pp. 140–1, note 1. The existence of this ninth, outermost orb, also called falak al-aflāk and falak al-aṭlas in the Arabic sources, was accepted by most Arabic philosophers and astronomers, although it was also a source of considerable controversy; in this respect, see Saliba, G., “Early Arabic critique of Ptolemaic cosmology: a ninth-century text on the motion of the celestial spheres,” Journal of the History of Astronomy, 25 (1994): 115–41CrossRefGoogle Scholar. Ibn Sīnā ascribes the discovery of this outermost orb to Ptolemy (Ibn Sīnā, The Metaphysics of the Healing, p. 317,9–13; id., Najāt, p. 303; id., Le livre de science (Dānesh-nāmeh), traduit par M. Achena et H. Massé (Paris, 1986), p. 142; the mathematical section of the latter work is nevertheless a compilation by Ibn Sīnā's pupil Jūzjānī), probably on the basis of certain passages in Planetary Hypotheses (Goldstein, “The Arabic version of Ptolemy's Planetary Hypotheses,” pp. 38–42), although the remarks on the ninth orb in this work are somewhat ambiguous.

8 Ibn Sīnā, Shifāʾ, Ṭabīʿiyyāt, vol. 2, Samāʾ, pp. 123–37; id., Ishārāt, vol. 2, pp. 226–27.

9 The Taḥrīr has been published in the mathematical section of the Cairo edition and Qum reprint of Shifāʾ but has not yet been the object of a sustained analysis. Ragep, F. J. and Ragep, S. P., “The astronomical and cosmological works of Ibn Sīnā: some preliminary remarks,” in Pourjavady, N. and Vesel, Ž. (eds.), Sciences, techniques et instruments dans le monde iranien (Xe–XIXe siècle), (Tehran, 2004), pp. 317Google Scholar, provide a list of Ibn Sīnā's works relating to astronomy, which indicates the extent of Ibn Sīnā's interest in several aspects of this science, from astronomical observations and the construction of instruments needed to conduct them to its more theoretical parts.

10 This is true especially with regard to the nine-tiered structure and the hierarchy of orbs, souls, and intellects that characterizes their cosmologies. In that sense, al-Fārābī's cosmological sketch in Ārāʾ anticipates the more elaborate discussions in the Metaphysics of Shifāʾ and Najāt; see al-Fārābī, Al-Farabi on the Perfect State: Abū Naṣr al-Fārābī's Mabādiʾ ārāʾ ahl al-madīna al-fāḍila: A Revised Text with Introduction, Translation, and Commentary, by R. Walzer (Oxford/New York, 1985), pp. 118–19 (henceforth Ārāʾ); and Ibn Sīnā, The Metaphysics of the Healing, pp. 326–34. But the present article will, at a further stage, question the degree of similarity between al-Fārābī's and Ibn Sīnā's cosmologies.

11 Ibn Sīnā, The Metaphysics of the Healing, p. 317,34–39. Cf. the similar approach of ʿAbd al-Laṭīf al-Baghdādī (d. 1231 CE), who inserts a whole section on hayʾa (astronomy) in his treatise on Book Lambda of Aristotle's Metaphysics; see Neuwirth, A., ʿAbd al-Laṭīf al-Baġdādī's Bearbeitung von Buch Lambda der aristotelischen Metaphysik (Wiesbaden, 1976), pp. 6473Google Scholar.

12 Ibn Sīnā, The Metaphysics of the Healing, pp. 14–5, translation slightly revised.

13 See the Mathematics of Shifāʾ, vol. 2, pp. 16–9, especially 19,5 ff., “On the sphericity of the heavens and their circular motion,” whose explanations rely on the physical theory of simple body (jism basīṭ), as well as pp. 24–6.

14 Translated by Ragep, S. in her entry “Ibn Sīnā,” in Hockey, Thomas et al. (eds.), The Biographical Encyclopedia of Astronomers, Springer Reference (New York, 2007), pp. 570–2Google Scholar. In this connection, see also Ragep and Ragep, “The astronomical and cosmological works of Ibn Sīnā,” pp. 10–11.

15 See Gutas, Avicenna and the Aristotelian Tradition, p. 54, from which the translation is taken.

16 Ibn Sīnā, Al-Samāʿ al-ṭabīʿī, pp. 41–3, especially 42,4–6.

17 Ibn Sīnā, Najāt, pp. 445–78; this treatise was composed or compiled by Jūzjānī, but it nevertheless faithfully conveys the master's views. In his account, the author alternates between the use of the term “orb” (falak/aflāk), which here clearly refers to physical bodies, and “circles” (sing. dāʾira), thus evoking the physical and mathematical aspects of his cosmology in a single text.

18 The most extensive and detailed analysis of the ancient conception of the relation between physics and astronomy is still to be found in Duhem, P., Le système du monde: histoire des doctrines cosmologiques de Platon à Copernic, 10 vols. (Paris, 1965 [1913–59])Google Scholar, vol. 1, pp. 468 ff.; vol. 2, pp. 59 ff. See also Bowen, A. C., “The demarcation of physical theory and astronomy by Geminus and Ptolemy,” Perspectives on Science, 15/3 (2007): 327–58CrossRefGoogle Scholar; and, for the Islamic world, Saliba, G., “Arabic versus Greek astronomy: a debate over the foundations of science,” Perspectives on Science, 8 (2000): 328–41CrossRefGoogle Scholar; Ragep, J. F., Naṣīr al-Dīn al-Ṭūsī's Memoir on Astronomy (al-Tadhkira fī ʿilm al-hayʾa), 2 vols. (New York, 1993)Google Scholar, vol. 1, pp. 41–6, 98–107; and finally, for al-Fārābī's views on the matter, Janos, D., “Al-Fārābī on the method of astronomy,” Early Science and Medicine, 15/3 (2010): 237–65CrossRefGoogle Scholar.

19 For astronomy's limited potential to explain the causes of celestial phenomena and the attitude of Arabic astronomers in this regard, see Ragep, Naṣīr al-Dīn al-Ṭūsī's Memoir on Astronomy, vol. 2, pp. 386–8.

20 Al-Fārābī, Ārāʾ, pp. 118–19. I have followed a common practice in the modern historiography on Arabic astronomy (ʿilm al-hayʾa) by translating falak as “orb” and kura as “sphere.” Yet it should be pointed out that this practice does not find strong support in the works of Ibn Sīnā and of many other Arabic thinkers, who use the two terms interchangeably to refer to the various planetary devices that move the planets. For this reason, I have sometimes translated kura as orb depending on the context. Moreover, with regard to the relation between geometric models and the celestial bodies, Ibn Sīnā uses both falak and kura to refer to concrete, physical orbs or spheres, and reserves the term dāʾira (circle) for the geometric models discussed in his commentary on Almagest; see especially The Metaphysics of The Healing, pp. 288,30–35; 317, passim; 325,30–326,8; cf. id., K. al-Ḥudūd/Livre des définitions, edited and translated by A.-M. Goichon (Cairo, 1963), pp. 26–7; cf. Ṭūsī, Sharḥ al-Ishārāt, vols. 3–4, 614–19; Neuwirth, ʿAbd al-Laṭīf al-Baġdādī's Bearbeitung, pp. 68–71, where falak and kura are used interchangeably to refer to the same heavenly bodies. Hence, the translations of falak and kura given in this article will always refer to physical entities.

21 Ibn Sīnā, K. al-Ḥudūd, p. 26, in the Arabic text.

22 Ibn Sīnā, The Metaphysics of the Healing, pp. 51,4–5; 324,35–40; 330,39–40; 331,33–34; 334,15–20.

23 See Lucchetta, F., “Le dieci questione di Avicenna,” Quaderni di studi arabi, 19 (2001): 101–34, 115Google Scholar.

24 Ibn Sīnā, Ishārāt, vols. 3–4, pp. 614–20. This passage is important for other reasons as well, to which I shall return later on.

25 By way of illustration, al-Bīrūnī (d. 1048 CE), Naṣīr al-Dīn al-Ṭūsī, and al-Jurjānī (d. 1413 CE) also define falak as a “spherical body” (jism kurī); see al-Bīrūnī, The Book of Instruction in the Elements of the Art of Astrology, translated by Wright, R. R. (London, 1934), p. 43Google Scholar; Ragep, Naṣīr al-Dīn al-Ṭūsī's Memoir on Astronomy, vol. 1, pp. 98–9; cf. Ṭūsī, Sharḥ al-Ishārāt, vols. 3–4, pp. 614–15; al-Jurjānī, K. al-Taʿrīfāt, ed. C. Flügel (Leipzig, 1845; Beirut, 1969), p. 176. Fakhr al-Dīn al-Rāzī (d. 1210 CE) is more hesitant and does not commit himself to the materiality of the orbs. In his al-Tafsīr al-kabīr (Beirut, 1980), vol. 25, p. 75, with regard to Qurʾān 36:40, he writes: “And so what is falak? We say that it is a spherical body [jism mustadīr], or a circular surface [satḥ mustadīr], or a circle (dāʾira)…” (my translation). By circle, Rāzī intends to say that it is merely a planetary trajectory conceived by the human mind, and therefore that it does not possess the extramental existence that a body (jism) or surface (satḥ) has.

26 Ibn Sīnā, Shifāʾ, vol. 2, Samāʾ, pp. 6–36, are pages devoted to the substance of the heavens; id., Risāla fī al-ajrām al-ʿulwiyya, in Tisʿ rasāʾil fī al-ḥikma wa-al-ṭabīʿiyyāt (Istanbul, 1298 AH), p. 48, and passim; see also Rashed, M., “The problem of the composition of the heavens (529–1610): a new fragment of Philoponus and its readers,” in Adamson, Peter, Baltussen, Han, and Stone, M.W.F. (eds.), Philosophy, Science and Exegesis in Greek, Arabic, and Latin Commentaries, 2 vols. (London, 2004)Google Scholar, vol. 2, pp. 35–58, at p. 41; and Goichon, A.-M., Lexique de la langue philosophique d'Ibn Sīnā (Paris, 1938), pp. 23Google Scholar.

27 The question of the conceptual versus extramental existence of the orbs was already discussed by ancient authors and also represents an important facet of the modern historiography on ancient astronomy and cosmology, especially as it is embodied in the works of Duhem, P., Sōzein ta phainomena: essai sur la notion de théorie physique de Platon à Galilée (Paris, 1908/1990)Google Scholar, and id., Le système du monde, vol. 2, pp. 36–8, 67 ff. Among the ancient philosophers, this question was discussed in particular by Simplicius and Proclus in his Hypotyposis, about which see Lloyd, G. E. R., “Saving the appearances,” The Classical Quarterly, 28 (1978): 202–23CrossRefGoogle Scholar; and Sorabji, R., The Philosophy of the Commentators, 3 vols. (London, 2004)Google Scholar, vol. 2, “Physics,” pp. 376–80; see also Evans, J., “The origins of Ptolemy's cosmos,” in Colafrancesco, S. and Giobbi, G. (eds.), Cosmology through Time: Ancient and Modern Cosmologies in the Mediterranean Area (Milano, 2003), pp. 123–35Google Scholar. For further insight into the Arabic tradition and into Duhem's interpretation of it, see: Ragep, J. F., “Duhem, the Arabs, and the history of cosmology,” Synthèse, 83 (1990): 201–14CrossRefGoogle Scholar.

28 This, I believe, is why al-Fārābī uses the term “bundle” (jumla) to describe the way in which the celestial bodies and orbs are organized in Ārāʾ, pp. 118–19. Accordingly, the term jumla designates not only the main orb and planet, but also the subordinate orbs and spheres associated with the planets. Other thinkers explicitly mention these minor bodies embedded in the main orbs; this is the case of Ṭūsī in his Sharḥ al-Ishārāt, vols. 3–4, pp. 615–17, and in his Tadhkira (Ragep, Naṣīr al-Dīn al-Ṭūsī's Memoir on Astronomy, II.2.4, vol. 1, pp. 110–11): “Each of these seven orbs [i.e., the planetary orbs] must be further divided into other orbs so that its planet's compound motion results from them, consistent with what is observed”; of al-Ījī's Kitāb al-Mawāqif fī ʿilm al-kalām (Cairo, c. 1980), p. 200; and of a treatise by ʿAbd al-Laṭīf al-Baghdādī (Neuwirth, ʿAbd al-Laṭīf al-Baġdādī's Bearbeitung, pp. 68–9). The latter refers to the nine main orbs as the “mother orbs” (ummahāt, p. 69,2) and also describes in detail the many minor orbs they contain.

29 Ṭūsī, Sharḥ al-Ishārāt, vols. 3–4, p. 617; Ragep, Naṣīr al-Dīn al-Ṭūsī's Memoir on Astronomy, vol. 1, pp. 50–3; cf. Neuwirth, ʿAbd al-Laṭīf al-Baġdādī's Bearbeitung, pp. 66–71, and 150–1. ʿAbd al-Laṭīf al-Baghdādī opts for a total of 55 or 77 orbs. Ptolemy in Planetary Hypotheses discusses various models consisting of a total of 22, 29, 34, and 41 orbs and spheres respectively, depending on what planetary devices are postulated; see Murschel, A., “The structure and function of Ptolemy's physical hypotheses of planetary motion,” Journal of the History of Astronomy, 26/1 (1995): 3361, 50–1CrossRefGoogle Scholar; and Ragep, Naṣīr al-Dīn al-Ṭūsī's Memoir on Astronomy, vol. 1, pp. 50–3.

30 Ṭūsī, Sharḥ al-Ishārāt, vols. 3–4, pp. 616–17; Ibn Sīnā's views on the multiplicity of the celestial motions will be discussed in detail later on.

31 Ibn Sīnā, Réfutation de l'astrologie, p. 139.

32 Ibn Sīnā, Mabdaʾ, pp. 61, 71. In the latter passage, Ibn Sīnā himself explains that by kura kulliyya, he means the main orb of a planet, e.g., Venus, even though this orb can then be further subdivided into various minor orbs and spheres. It is worth noting once more that Ibn Sīnā uses kura and falak interchangeably to refer to the celestial orbs.

33 As already mentioned, al-Fārābī limits his cosmological descriptions to these main orbs, although it is likely that he believed in the existence of a greater number of orbs; see Ārāʾ, pp. 119–21. For the late-antique background, see I. Bodnár, “Alexander of Aphrodisias on celestial motions,” Phronesis, 17/2 (1997): 190–205; and especially 198: “My contention then is that Alexander after talking about the sphere of Saturn, Jupiter etc., could keep the possibility open to talk, on occasion, about the very same entity as a bundle of different spheres, in whatever pattern they are arranged by a viable astronomical theory.” Sorabji's claim, The Philosophy of the Commentators, vol. 2, “Physics,” pp. 342–3, that Alexander reduced the number of orbs from 55 to 7 is likely to be based on a misunderstanding of the kind discussed above. For Alexander would surely have been aware that 7 orbs would have been insufficient to account for all the planetary motions. Rather, it would seem that in the passages cited by Sorabji, Alexander is only referring to the main orbs; again, cf. Bodnár.

34 Ibn Sīnā, Ishārāt, vols. 3–4, pp. 620–1; id., Samāʾ, pp. 45–6. This view is then condoned by Ṭūsī (Sharḥ al-Ishārāt, vols. 3–4, pp. 615, 620); cf. al-Ījī, Mawāqif, pp. 200 ff.; and Fakhr al-Dīn al-Rāzī, who lists several different theories concerning this problem in his al-Mabāḥith al-mashriqiyya, ed. Muḥammad al-Muʿtaṣim bi-llāh al-Baghdādī, 2 vols. (Beirut, 1990), vol. 2, p. 105: first, the planets alone move in immobile orbs; second, both the orbs and the planets have independent motions; third, the planets are fixed on the orbs and are carried along by the motion of the orbs.

35 Ibn Sīnā, Mabdaʾ, p. 68. This is quite odd, for Ptolemy himself did not uphold such a theory. It is unclear to me what lies at the origin of this misconception.

36 McGinnis, “Positioning heaven.”

37 Ibn Sīnā, K. al-Ḥudūd, p. 29; id., Najāt, pp. 445 ff. This appears to have been a major problem for most Arabic philosophers and astronomers, and not just Ibn Sīnā; see Ragep, Naṣīr al-Dīn al-Ṭūsī's Memoir on Astronomy, vol. 2, pp. 408–12.

38 Insight into this complicated system is given by Duhem, Le système du monde, vol. 2, pp. 90–4, with regard to Ptolemy and other ancient astronomers; it could also be described by Ṭūsī in his Sharḥ al-Ishārāt, vols. 3–4, pp. 616–17, although his comments are vague.

39 Ibn Sīnā, The Metaphysics of the Healing, p. 323,20–25.

40 This term is the translation of the Greek planētai. It is important to stress that the plurality of planetary motions is frequently mentioned by Ibn Sīnā, who recognized the complexity of these heavenly phenomena (Ibn Sīnā, The Metaphysics of the Healing, p. 317,34–39; id., Mabdaʾ, p. 62). Although the celestial bodies possess harmonious, circular motions, these motions are nevertheless varied and multiple. As we shall see, Ibn Sīnā's recognition of this basic fact inaugurated a series of metaphysical and astronomical problems for the shaykh al-raʾīs, who was obviously puzzled as to how to account for the causes of these phenomena. The difficulty appears to have been the following: when trying to establish the principles underlying celestial motion, it is not sufficient to explain why the celestial bodies move, or why they move in a circular fashion; in addition, one must account for the causes of the plurality and diversity of their motions. But each one of these questions might require one to posit different principles, thus making the endeavour much more complex.

41 Ibn Sīnā, Samāʾ, p. 47,13–15; id., Réfutation de l'astrologie, p. 37/135, and Michot's comments note 3; this view is accepted by Ṭūsī, Sharḥ al-Ishārāt, vols. 3–4, p. 619.

42 The ensoulment of the heavens was a standard view in ancient and medieval thought, which finds support in Plato's Timaeus 36E-39A and Laws 896B-897C and 967D-E, in the Platonizing work Epinomis 981E and 983A-C, and in a more implicit way in some Aristotelian works, such as De caelo II.2, 12, and Metaphysics XII.8.1074b1–15. Surveying the reception of these texts in late-antiquity would take us too far from the present subject, but a key work from the Greek background translated into Arabic should be mentioned here: Alexander of Aphrodisias' Principles of the Cosmos or Fī mabādiʾ al-kull (henceforth Mabādiʾ), which was edited, translated, and analyzed by C. Genequand; see Alexander of Aphrodisias on the Cosmos (Leiden/Boston, 2001)Google Scholar. This treatise discusses several cosmological concepts (including the role of soul and intellect in celestial motion) that were later adopted by al-Fārābī and Ibn Sīnā. It should therefore be regarded as a foundational work in the development of Islamic cosmology; see also Endress, G., “Alexander Arabus on the first cause: Aristotle's first mover in an Arabic treatise attributed to Alexander of Aphrodisias,” in D'Ancona, C. and Serra, G. (eds.), Aristotele e Alessandro di Afrodisia nella tradizione araba (Padova, 2002), pp. 1975Google Scholar, especially 37–46; and Wolfson, H. A., “The problem of the souls of the spheres from the Byzantine commentaries on Aristotle through the Arabs and St. Thomas to Kepler,” Dumbarton Oaks Papers, 16 (1962): 6593CrossRefGoogle Scholar. The most thorough description of these celestial souls in Ibn Sīnā's cosmology was given by Michot, J., La destinée de l'homme selon Avicenne (Louvain, 1986), pp. 110–18Google Scholar. However, Michot's claim (111, 113, note 36) that the shaykh al-raʾīs relied on De caelo for this aspect of his cosmology seems very unlikely, as this theory is only vaguely alluded to in this work and in any case not developed at any length. Rather, it seems more plausible that Ibn Sīnā was drawing on the late-antique commentaries on Aristotle's De caelo and Metaphysics as well as on other cosmological works, such as the Arabic version of Alexander's On the Principles of the Cosmos, which discuss the ensoulment of the heavenly bodies in depth.

43 Ibn Sīnā, The Metaphysics of the Healing, p. 311,31–32; Genequand, Alexander of Aphrodisias on the Cosmos, pp. 52–3. This view also seems to have been common in ninth- and tenth-century philosophical circles in Baghdad, as it is mentioned by al-Fārābī (Ārāʾ, p. 120; Kitāb al-Siyāsa al-madaniyya al-mulaqqab bi-mabādiʾ al-mawjūdāt, edited by Najjār, F. M. [Beirut, 1964], p. 41)Google Scholar and Abū Sulaymān al-Sijistānī in his cosmological treatises (Kraemer, J. L., Philosophy in the Renaisance of Islam: Abū Sulaymān al-Sijistānī and his Circle [Leiden, 1986], pp. 280–2, 284)Google Scholar.

44 Ibn Sīnā, The Metaphysics of the Healing, p. 312,4-6.

45 Ibn Sīnā, The Metaphysics of the Healing, p. 311,27–31.

46 Genequand, Alexander of Aphrodisias on the Cosmos, pp. 24–5; for the concept of imitation in late-antique cosmology, see the sources collected in Sorabji, The Philosophy of the Commentators, vol. 2, “Physics,” pp. 52, 338.

47 Ibn Sīnā, The Metaphysics of the Healing, pp. 315,15; 316,6; id., Mabdaʾ, p. 59.

48 See Ibn Sīnā, Réfutation de l'astrologie, pp. 37–8/135–9; id., Ishārāt, vols. 3–4, pp. 614–20; id., Mabdaʾ, p. 71, where the theory that only the planets are ensouled is ascribed to a “certain group among the learned” and thus does not convey Ibn Sīnā's own view on this issue. In the Ishārāt passage, Ibn Sīnā ascribes a “principle of circular motion for itself” to each component of the heavens – planets and orbs – which in this context must refer to the celestial soul and not to the separate intellect or to aether. This at any rate is how Ṭūsī understands Ibn Sīnā in his Sharḥ al-Ishārāt, vols. 3–4, p. 619, and it is also supported by several passages in The Metaphysics of the Healing, such as p. 325,25–30. As we shall see, the ensoulment of each celestial entity is a requisite for Ibn Sīnā's celestial kinematics to be coherent.

49 Wisnovsky, Avicenna's Metaphysics in Context, pp. 108–12, 188–95, gives valuable insight into the concept of perfection in al-Fārābī's and Ibn Sīnā's cosmologies and into some of the Greek and especially Proclean precedents to their views. There is nevertheless some ambiguity as to exactly how the separate intellects relate to the celestial souls, for we have seen that the latter are endowed with a rational faculty and are also capable of contemplating the higher immaterial principles. The problem concisely put is that the celestial souls contemplate the separate intellects, but since Ibn Sīnā follows Aristotle in holding that in the act of intellection, thinker and object of thought become identical, one wonders in what sense – or to what extent – the celestial souls remain distinct from the separate intellects in this very act. This ambiguity is reinforced by the fact that Ibn Sīnā (Najāt, pp. 647–8) compares the relation between the celestial souls and the separate intellects to that between the human soul and the Agent Intellect. In both cases, then, one faces the problem of explaining the nature of this relation: is it through contact, conjunction, fusion, or some other means? As Ibn Sīnā is adamant that the celestial souls are located in a material substrate, one may say that only the intellective part of the celestial souls connects with the separate intellects, in the same way that only the intellectual part of the human soul connects with the Agent Intellect. At any rate, Ibn Sīnā consistently differentiates the separate intellects from the celestial souls and the material substrates in which they inhere, and on this distinction rests one of the principles of his theory of celestial kinematics.

50 Al-Fārābī, Risāla fī al-ʿaql, edited by M. Bouyges, tome VIII, fasc. 1, XXIV (Beirut, 1938), p. 34; Ibn Sīnā, The Metaphysics of the Healing, pp. 307,15; 317,7–8; 328,28; id., Mabdaʾ, p. 51; id., K. al-Ḥudūd, p. 22, or 15 in the Arabic text. It is clear that this identification was inspired by Metaphysics, Book Lambda 7 and 8, and the authority of Aristotle and later Peripatetic commentators is in fact invoked for support in this passage of Shifāʾ.

51 Ibn Sīnā, The Metaphysics of the Healing, pp. 317,1–5; 318,2–5.

52 Ibn Sīnā, The Metaphysics of the Healing, p. 317,1–6. One should note that the Agent Intellect is not directly involved in celestial motion and has for chief function to govern sublunary phenomena, such as the preparation of prime matter and the mixture of elements, and it also has an important role to play in human intellection.

53 Ibn Sīnā, Mabdaʾ, p. 61: “And so you know that the substance of this desired good [the First Cause] is one and that it is not possible that the mover of the whole heaven be more than one, although there is for each heavenly orb a proximate mover that characterizes it [the soul], as well as a desired beloved that characterizes it [the separate intellect], according to the opinion of the philosopher [Aristotle], Alexander, and Themistius and the wisemen [ʿulamāʾ] of the Peripatetic school” (my translation). The distinction between the separate intellects and the souls of the orbs also appears in Ibn Sīnā's Sharḥ Kitāb Ḥarf al-lām, in Badawī, A. R. (ed.) Arisṭū ʿinda al-ʿArab: dirāsa wa-nuṣūṣ ghayr manshūra (Kuwayt, 1947), pp. 2233Google Scholar, 29, and is attributed to Aristotle himself. Ibn Sīnā's interpretation of Alexander's cosmology was probably chiefly based on Mabādiʾ, but this text is in fact highly ambiguous when it comes to the movers, particularly with regard to the questions of whether they are separate from the orbs and how many they are; for a discussion of this topic, see Genequand's introduction in Alexander of Aphrodisias on the Cosmos, especially p. 14; and Endress, “Alexander Arabus,” pp. 45–6, 57 ff. Moreover, there is the problem – not directly relevant here – of how the cosmology of the Alexander arabus compares to that of the Alexander graecus, since the Greek and Arabic texts ascribed to Alexander are not fully consistent with regard to these issues; see Bodnár, “Alexander of Aphrodisias on celestial motions”; Sharples, R. W., “Pseudo-Alexander on Aristotle, Metaphysics Λ,” in Movia, G. (ed.), Alessandro di Afrodisia e la “Metafisica” di Aristotele (Milano, 2003), pp. 187219Google Scholar; Sorabji, The Philosophy of the Commentators, vol. 2, “Physics,” pp. 340–1. As for Themistius, Ibn Sīnā is probably referring to his paraphrase of Book Lambda, which was translated into Arabic and was accessible to the falāsifa, although here again the question of how Themistius conceives of the celestial movers requires a separate study; see Paraphrase de la métaphysique d'Aristote (livre lambda), traduit de l'hébreu et de l'arabe, introduction, notes et indices par R. Brague (Paris, 1999), especially pp. 102–3. Cf. Abū Sulaymān al-Sijistānī, who dealt with similar issues and probably relied on the same sources, which he nevertheless interpreted differently. Al-Sijistānī, like Ibn Sīnā, describes God as the mover of the entire heaven, but unlike Ibn Sīnā he construes the other movers as being inherent in the orbs; see Kraemer, Philosophy in the Renaissance of Islam, pp. 274–92. Returning to Ibn Sīnā, it is interesting to note that he upheld a harmonizing reading of Aristotle's cosmology, according to which there are no intrinsic contradictions to be found in Aristotle's various cosmological doctrines. Consequently, any interpretive problem must be due to one's own limited philosophical insight; see Ibn Sīnā, Najāt, p. 302; and id., The Metaphysics of the Healing, p. 316,35–37.

54 In downplaying the role of aether in his cosmology, Ibn Sīnā is consciously or unconsciously continuing a trend of skepticism toward and criticism of this Aristotelian doctrine that developed in the works of some ancient commentators; see Sorabji, The Philosophy of the Commentators, vol. 2, “Physics,” pp. 357–71. Ibn Sīnā, however, does not deny the existence of a special celestial substance, but rather minimizes its agency in causing celestial motion.

55 Badawī (ed.), Arisṭū ʿinda al-ʿArab, p. 19; Themistius, Paraphrase de la métaphysique d'Aristote, p. 103.

56 Previous studies on Ibn Sīnā's cosmology have in general uncritically accepted the theory of the ten separate intellects: see Corbin, H., Histoire de la philosophie islamique (Paris, 1964), pp. 242–3Google Scholar; A.-M. Goichon, La distinction de l'essence, pp. 236–7; Gardet, L., La pensée religieuse d'Avicenne (Ibn Sīnā) (Paris, 1951), pp. 52–3Google Scholar; Davidson, Alfarabi, Avicenna, and Averroes on Intellect, pp. 74–5, 82, (on page 74, note 2, Davidson acknowledges the problem of the number of intellects in Ibn Sīnā's cosmology, but does not address it); Nasr, An Introduction to Islamic Cosmological Doctrines, pp. 202–4; Netton, Allah Transcendent, pp. 162–5; Goodman, L. E., Avicenna (London/New York, 1992), p. 82Google Scholar; Maróth, “The ten intellects cosmology and its origin”; Smet, D. De, La quiétude de l'intellect: néoplatonisme et gnose ismaélienne dans l'œuvre de Ḥamīd al-Dīn al-Kirmānī (Xe/XIe s.) (Leuven, 1995), pp. 273–5, 285Google Scholar; and O. Lizzini, Le cosmologie di Alfarabi e di Avicenna, in Cosmogonie e cosmologie nel Medioevo, Atti del XV Colloquio della SISPM, Società Italiana per lo Studio del Pensiero Medievale (Catania, 22–24 settembre 2006), a cura di C. Martello, C. Militello, Andrea Vella, Textes et Études du Moyen Âge 46 (Louvain-la-Neuve, 2008), pp. 195–214. A. Hasnawi, “Fayḍ,” in Encyclopédie philosophique universelle, 2 vols., volume dirigé par S. Auroux (Paris, 1990), “Les notions philosophiques,” vol. 2, t. 1, pp. 966–72, is to my knowledge the only scholar to have criticized this assumption.

57 Ibn Sīnā, The Metaphysics of the Healing, p. 325,20–23, translation slightly revised.

58 Marmura translates this term in the singular, “sphere,” although the Arabic reads kurāt. This has the unfortunate effect of changing the entire meaning of the sentence, since Ibn Sīnā's point here is based on the distinction between the main orbs of the planets and the other subordinate orbs and spheres that they contain and that are instrumental in producing the irregular motions of the planets. Bertolacci's and Lizzini's translations, which preserve the plural, should be preferred; see Libro della guarigione, Le cose divine di Avicenna (Ibn Sīnā), a cura di A. Bertolacci (Turino, 2007), pp. 734–5; Metafisica: nuova edizione rivedutta e coretta, con testo arabo e latino, a cura di O. Lizzini e P. Porro (Milano, 2006), pp. 920–1. Furthermore, one should favour “planet” over Marmura's rendering “star” as a translation of kawkab in this same passage, since Ibn Sīnā is referring in this case to the seven planets, not to the fixed stars located in the eighth orb.

59 Ibn Sīnā, The Metaphysics of the Healing, pp. 325,30–326,8, translation slightly revised, my emphasis. It is likely that this passage is at the origin of the widely held misconception that Ibn Sīnā adopted the ten-intellect theory, for it has been interpreted in this way by some scholars; see, for instance, De Smet, La quiétude de l'intellect, p. 285. Yet it should be noted that Ibn Sīnā does not explicitly endorse the ten-intellect theory in this passage; he is merely describing the two main cosmological models developed by philosophers with regard to the separate intellects. These two models have been briefly but cogently analyzed by Hasnawi, “Fayḍ,” pp. 966–72. Much of the following discussion may be seen as an attempt to elaborate on some of the points outlined in Hasnawi's article.

60 Cf. Ibn Sīnā, Najāt, pp. 648–9; id., Mabdaʾ, pp. 67–8. It is quite intriguing that a similar description of these two kinematic models appears in Shifāʾ, Najāt, and Mabdaʾ in virtually the same form. On the one hand, it points to the obvious importance Ibn Sīnā ascribed to this cosmological question and to its perceived difficulty. On the other hand, it also says something about the composition and chronology of these texts, which rely on one another in terms of content and doctrine; on this issue, see Gutas, Avicenna and the Aristotelian Tradition, pp. 98–145.

61 Or, I should say, as Ibn Sīnā interpreted Book Lambda 8, for there is no consensus among historians of philosophy concerning Aristotle's cosmology in this passage. What is important here is that Ibn Sīnā interpreted Aristotle as positing a plurality of separate movers, which amount to the same number as the orbs and motions.

62 Ibn Sīnā, Sharḥ Kitāb Ḥarf al-lām; Gutas, Avicenna and the Aristotelian Tradition, p. 28, for the reference to Ibn Sīnā's autobiography.

63 It is perplexing that the text has the plural form kurāt, since the description concerns the orb of the fixed stars, which is unique and which is otherwise referred to in the singular in this passage. This oddity can be explained either by an editing mistake or by Ibn Sīnā's potential reference to the hypothesis that the stars are fixed on various smaller orbs within the main orb of the fixed stars.

64 Ibn Sīnā, Mabdaʾ, p. 71, my translation.

65 Two additional passages should be mentioned here to complete Ibn Sīnā's depiction of this kinematic model: al-Nafs, Shifāʾ, p. 11,9–15; and Samāʾ, pp. 45 ff. In the latter work, which I paraphrase below, Ibn Sīnā begins the chapter entitled “On the motions of the planets” by outlining the various kinematic theories in use presumably during his time. He first draws a distinction between three groups: 1) those who hold that the heavens are immobile and that the planets move by piercing the orbs; 2) those who hold that the heavens and planets move in opposite directions and that the planets pierce the orbs; and 3) those who believe that the planets are fixed on their orbs and move with their motion. Ibn Sīnā then goes on to say that the latter group is divided into two positions: a) on the one hand, there are those who argue that the planet is the first principle for the emanation of a motive power (al-mabdaʾ al-awwal li-fayḍān quwwat al-taḥrīk ʿanhu) and that it is like the brain or heart in the animal; b) on the other hand, there are those who make the orb (jirm al-samāʾ) the principle of motion for the planets. This excerpt indicates that medieval Muslim thinkers could choose among a wide variety of cosmological theories. Position 3)a), however, must be identified with the ‘first kinematic model’ that Ibn Sīnā exposes in Shifāʾ, Najāt, and Mabdaʾ. As in these other works, it is the planets, not the orbs, which are the main principle of motion, and furthermore these texts all mention the emanative powers of the planets as the main cause of motion.

66 Goldstein, “The Arabic version of Ptolemy's Planetary Hypotheses,” p. 40: idhā taḥarraka bi-ḥarakatihi al-khāṣṣa lahu kāna ibtidāʾ tilka al-ḥaraka min al-quwwa al-nafsāniyya allatī fīhi thumma ḥadatha [?] ʿan hādhihi al-quwwa al-inbiʿāth thumma yaṣīru dhālika ilā al-ʿaṣab thumma min al-ʿaṣab ilā al-rijlayn fī al-mathal aw ilā al-yadayn aw al-ajniḥa…

67 Goldstein, “The Arabic version of Ptolemy's Planetary Hypotheses,” p. 41: kull wāḥid min al-kawākib fī martaba[ti]hi lahu quwwa nafsāniyya wa-innahu yuḥarriku dhātahu wa-yuʿṭī al-ajsāma al-muttaṣilata bihi bi-al-ṭabʿ ḥaraka ibtidāʾihā…

68 Goldstein, “The Arabic version of Ptolemy's Planetary Hypotheses,” p. 36: wa-li-kull ḥaraka min hādhihi al-ḥarakāt al-mukhtalifa fī kammiyya aw fī al-nawʿ jism taḥarraka ʿalā al-aqṭāb wa-fī ḥayyiz wa-makān khāṣṣ lahu ḥaraka irādiyya wa-ʿalā ḥasabi quwwa kull wāḥid min al-kawākib allatī minhā yakūnu ibtidāʾ al-ḥaraka allatī tanbaʿithu ʿan al-quwā al-raʾīsa allatī hiya mithl al-quwā allatī fīnā wa-tuḥarriku al-ajsām al-mujānisa lahā allatī hiya shibh al-ajzāʾ al-ḥayawān al-kullī…

69 Murschel, “The structure,” p. 39; see also Sambursky, S., The Physical World of Late Antiquity (London, 1962), pp. 142–4Google Scholar.

70 Ibn Sīnā, Mabdaʾ, p. 56; Najāt, p. 624.

71 This being said, there are also major differences between these texts. Ptolemy in Planetary Hypotheses, rejects the Aristotelian unmoved movers, or rather, he provides the term “mover” with a completely different meaning by applying it to the orbs themselves. Thus, for Ptolemy, a mover (muḥarrik) is a planetary orb; see Goldstein, “The Arabic version,” pp. 42–4; Murschel, “The structure,” pp. 41–2. Ibn Sīnā, on the other hand, applies the term “mover” to both the separate intellects (the remote movers) and the celestial souls (the proximate movers). He thus preserves the Aristotelian concept of celestial mover, although he adapts it to his own cosmology. In addition, Ibn Sīnā mentions that these powers emanate (tafīḍu) from the planets, a term that does not appear in Planetary Hypotheses. Finally, it is possible that the concept of quwwa is not exactly the same in the Ptolemaic and Avicennan contexts. While Ptolemy seems to use quwwa to refer to a psychological faculty inherent in the planets, Ibn Sīnā uses this term to express both a psychological faculty and the actual emissions that are being sent from the planetary soul to the other corporeal components. In spite of this, the connection between quwwa and motion is clear enough in the two texts, especially since quwwa is explicitly connected with the planetary souls. Hence, in spite of important differences, the kinematic model described by Ibn Sīnā finds its closest parallel in Planetary Hypotheses. There is also the question of whether this model could have been informed to some extent by Proclus' cosmology, in which the planets are described as the “chiefs” of their systems and as the principles of their own motion; see Siorvanes, L., Proclus: Neoplatonic Philosophy and Science (Edinburgh, 1996), pp. 272–73, 282 ffGoogle Scholar. However, in Proclus' cosmology, the planets are not fixed on their orbs but travel unhindered through the heavens, for Proclus does not conceive of the orbs as material bodies but as regions of space (Siorvanes, Proclus, pp. 282 ff.).

72 Ibn Sīnā, Mabdaʾ, pp. 68, 71.

73 It is, however, unclear whether these two thinkers explained celestial motion by means of emanating planetary powers in the way described by Ibn Sīnā. To my knowledge, no evidence in al-Fārābī's works can unambiguously support such a conclusion. For al-Kirmānī's cosmology, see De Smet, La quiétude de l'intellect, especially pp. 270–84, 313–15; id. “Al-Fārābī᾿s influence on Ḥamīd al-Dīn al-Kirmānī's theory of intellect and soul,” in Adamson, P. (ed.) In the Age of al-Fārābī: Arabic Philosophy in the Fourth/Tenth Century (London/Turin, 2008), pp. 131–51Google Scholar, but further research on this thinker's theories of celestial kinematics is necessary to settle this point.

74 Ṭūsī contrasts the two models in the same manner that is found in Shifāʾ. This is noteworthy since Ibn Sīnā himself does not discuss them in Ishārāt. While Ṭūsī's analysis follows that of the shaykh al-raʾīs quite closely, it also introduces several details worthy of note. For instance, Ṭūsī explains that in the first model, each planet and its corresponding orbs are like a single animal or ensouled being; that the soul pertains primarily to the planet and secondarily to the corresponding orbs, just as in the case of an animal the soul is located primarily in the heart and only secondarily in the other organs; and that the motive power is emitted (munbaʿitha) from the planet (heart) to the orbs (members) (see Sharḥ al-Ishārāt, vols. 3–4, pp. 618–19). Talkhīṣ fī mā baʿda al-ṭabīʿa, edited by ʿUthmān Amīn (Cairo, 1958), p. 134, section 22, which can only be ascribed to Ibn Rushd with some caution, also compares these two models. In this respect the author writes: “As to [the question of] whether it is possible to posit fewer movers than the number [which we have indicated, i.e., 47 or 55], as some of them think [i.e., a group of philosophers], this is because they assign to each [main] orb only one mover which moves the planet only, from which [i.e., the planet] then emanates powers [quwan] that coordinate the other motions which characterize this planet and which occur due to it…” Ibn Rushd's description closely mirrors the one that can be found in Shifāʾ, and together the two texts show that the problem of the number of unmoved movers/separate intellects and their relation to the orbs was regarded as an important cosmological problem by several Arabic thinkers, including Ibn Sīnā and Ibn Rushd.

75 Again, one should stress that for Ptolemy, the “movers” are the main orbs themselves, and he does not adhere to the Aristotelian theory of separate movers that move the orbs through desire and contemplation. Moreover, although Ptolemy attributes psychological powers to the planets in Planetary Hypotheses, he does not articulate a theory of intellection along the lines of al-Fārābī's and Ibn Sīnā's doctrines.

76 Ibn Sīnā, The Metaphysics of the Healing, pp. 329,28–29; 330,35–36, where he merely states that there are “many” separate intellects.

77 I take this to be a reference to Ibn Sīnā's Taḥrīr al-Majisṭī, contained in the Mathematics section of Shifāʾ. It should be said nevertheless that this statement is quite odd, for this commentary would not have been an adequate place for a discussion of the separate intellects and the orbs and of how they relate to each other. Given its skopos and genre, one rather would expect Ibn Sīnā to have addressed the problem of motion in this commentary from a mathematical angle, that is, through geometric figures. Moreover, knowledge of the number of orbs in itself cannot solve the problem of the number of separate intellects that Ibn Sīnā raises in the Metaphysics of Shifāʾ, since the multiple motions of these orbs can be explained by using either one of the two kinematic models he describes, which require a different number of intellects. Accordingly, the key to this problem as it is defined in the Shifāʾ passage lies not in the number of orbs, but rather in the interpretation of the role of the planetary souls in causing celestial motion. There is thus much ambiguity as to what exactly has been “settled” in the Mathematics of Shifāʾ and as to how this relates to the present metaphysical discussion on the separate intellects. In fact, the coherence of this passage seems to have been significantly affected by the process of copying and editing that characterized the composition of Shifāʾ, which drew upon and modified many excerpts from earlier works such as Mabdaʾ. To make sense of this passage, it is necessary to rely on Mabdaʾ, pp. 67–8, which provides a similar but longer version of the same discussion. In the passage immediately following this one, Ibn Sīnā explains that if the ten-intellect theory is set aside (i.e., together with the theory of emanating planetary powers), then the number of celestial motions must be counted in order to infer the number of separate principles, which will be equal. In this case, the reference to his Taḥrīr al-Majisṭī would make more sense, since this work would have examined in detail the number of motions that should be ascribed to each planet, and it could therefore have been used as a starting point for fixing the number of orbs and separate movers. Consequently, what was discussed in the Mathematics was most likely not the number of separate intellects, in spite of what Y. J. Michot suggests in his translation of Mabdaʾ (Ibn Sīnā, Le livre de la genèse et du retour, Version exploratoire, traduction française intégrale par Y. J. Michot (Oxford, May 2002), p. 49, available online at, but rather the number of motions, which would in turn enable a conclusion concerning the number of intellects in the appropriate context, i.e., the metaphysical sections of Ibn Sīnā's philosophical works.

78 Ibn Sīnā, Mabdaʾ, pp. 68, 71; id., Samāʾ, pp. 45–6.

79 Ibn Sīnā, The Metaphysics of the Healing, p. 317,20–35.

80 Ibn Sīnā, The Metaphysics of the Healing, p. 325,2–5. A similar theory is ascribed to Aristotle in Ibn Sīnā's Sharḥ Kitāb Ḥarf al-lām, pp. 28–9.

81 Ibn Sīnā, The Metaphysics of the Healing, p. 317,34–39.

82 Ibn Sīnā, The Metaphysics of the Healing, p. 323,20 ff.; id., Najāt, pp. 634–6, 647.

83 It is noteworthy that in all the previous passages Ibn Sīnā takes for granted the fact that the intellectual movers are separate principles and that they are not identifiable with the souls that inhere in the orbs. This view is also found in the extant excerpts of his commentary on Book Lambda, the Sharḥ Kitāb Ḥarf al-lām, p. 28, where he attributes to Aristotle the theory that there are many separate movers and principles (al-muḥarrikāt al-mufāriqa and al-jawāhir al-mufāriqa). In the Arabic versions of Book Lambda themselves, however, the term mufāriq to my knowledge does not appear in connection with the movers, an ambiguity which may have led other Arabic thinkers to conceive of them as being inseparable from the orbs; this seems to have been the case of al-Sijistānī and Ibn Rushd; see Kraemer, Philosophy in the Renaissance of Islam, pp. 285–92; Genequand's, C. introduction in Ibn Rushd's Metaphysics: A Translation with Introduction of Ibn Rushd's Commentary on Aristotle's Metaphysics, Book Lām (Leiden, 2004), especially pp. 40–1Google Scholar.

84 Ṭūsī, Sharḥ al-Ishārāt, vols. 3–4, p. 625, my translation; see also p. 619, where Ṭūsī ascribes to Ibn Sīnā the view that each celestial orb – including the minor ones – is ensouled.

85 Ṭūsī, Sharḥ al-Ishārāt, vols. 3–4, pp. 617, 625. Ṭūsī adds that this approach is vindicated by proof (dalīl), although the intellects could be even more numerous than one might think. Ṭūsī is here probably alluding to the existence of additional planetary orbs or to an alternative organization of the fixed stars, which could be disseminated on various different orbs.

86 Ibn Sīnā, Mabdaʾ, pp. 67–8, my translation. In spite of its early date of composition, the cosmological material in Mabdaʾ overlaps considerably with that in Najāt and Shifāʾ, a not surprising fact given that it was used for the redaction of these later philosophical summae. Hence, the results of an analysis of Mabdaʾ can be legitimately and fruitfully applied to these other works, although the chronological factor should be borne in mind to explain certain discrepancies. Moreover, Mabdaʾ is a crucial text that should be included in a reconstruction of Ibn Sīnā's cosmology, as it also contains additional material not preserved in the later works.

87 The elaboration of the theories of the epicycles and eccentrics was a long process in which Apollonius of Perga (third century BCE) and Hipparchus (second century BCE) played the major roles, although Ptolemy (second century CE) was the first to use them systematically.

88 This information is reported by Simplicius in his commentary on De caelo, On Aristotle's On the Heavens 2.10–14, translated by Ian Mueller (Ithaca, N.Y., 2005), p. 507,10–15.

89 It is unclear to me why Ibn Sīnā ascribes to Ptolemy the view that the celestial bodies transpierce one another, as no such statements can be found in Planetary Hypotheses. Moreover, one may wonder what this digression has to do with the problem at hand, namely, the number of motions and separate intellects.

90 In order to avoid potential misunderstandings, I should stress that the “doctrine of Ptolemy” (raʾy Baṭlamiyūs and madhhab Baṭlamiyūs) discussed in this passage of Mabdaʾ does not refer to the ‘first kinematic model’ of ten separate intellects, in spite of the fact that the latter relies heavily on Planetary Hypotheses, but rather to (Ibn Sīnā's account of) Ptolemy's views on how the planets move through the heavens and on the number of planetary motions. Ptolemy's and Aristotle's theories are therefore examined as two solutions to the question of how many motions, orbs, and (ultimately) movers there are, it being assumed that this number is any case greater than ten.

91 This reconciliation is likely to have been effected by some of the Greek commentators, notably Alexander and Simplicius in his commentary on De caelo; see Duhem, Le système du monde, vol. 2, pp. 99 ff.; Sorabji, The Philosophy of the Commentators, vol. 2, “Physics,” pp. 342–3, 376–7. It is nonetheless unclear how these thinkers adapted the epicycles and eccentrics to their own cosmological systems and how these astronomical theories interact with the theory of the unmoved movers; more research needs to be carried out on these cosmological aspects of late-antique philosophy.

92 Ibn Sīnā, Sharḥ Kitāb Ḥarf al-lām, p. 29.

93 It is notable that Ibn Sīnā includes epicyclic spheres in this number in a way similar to the Mabdaʾ passage, which also ascribes these devices to Aristotle.

94 Ibn Sīnā, Réfutation de l'astrologie, pp. 38/139, my translation. This last comment probably refers to the fixed stars, which according to Ibn Sīnā could be located on several different orbs and not be contained by a single orb. This passage should be read in light of Samāʾ, p. 46,5–7, where Ibn Sīnā envisages this possibility. I cannot in this article discuss the place of astronomical observation in Ibn Sīnā's method; on this very interesting question, which deserves to be examined more thoroughly, see Michot's remarks in Ibn Sīnā, Réfutation de l'astrologie, pp. 126–7, note 3; and id., The Metaphysics of the Healing, p. 291,18–35.

95 This point is forcefully made by Ṭūsī in his Sharḥ al-Ishārāt, vol. 3–4, p. 619, where he ascribes to the “master” (al-shaykh) the view that the orbs and planets (kawākib) all possess their own separate movers. It is even possible that Ṭūsī also intended to refer to the stars in this passage, although the ambiguity of the Arabic term kawākib is problematic, since it can refer to both the stars and planets.

96 These results thus confirm Hasnawi's hypothesis in “Fayḍ,” p. 968. I have in what precedes focused on Ibn Sīnā's major philosophical treatises and do not wish to devote too much attention at this point to his minor treatises, partly because of the uncertainty surrounding their authenticity. Yet mention must be made of the fact that they often contain material that is difficult to reconcile with, or even contradicts, the previous considerations. For example, in R. fī ithbāt al-nubūwwāt, ed. by Marmura, M. (Beirut, 1968), p. 53Google Scholar, Ibn Sīnā refers to nine orbs and to the eight angels (here identified as intellects?) mentioned in Qurʾān 69:17. However, the context is problematic, since Ibn Sīnā is in this passage relating the “philosophical discourse” (al-kalām al-falsafī) on this verse alongside that of the traditionists without necessarily endorsing this thesis. In R. fī al-malāʾika, in al-Tafsīr al-qurʾānī wa-al-lugha al-ṣūfiyya fī falsafat Ibn Sīnā, edited by ʿAṣī, H. (Beirut, 1983), pp. 289–94Google Scholar, on the other hand, Ibn Sīnā explicitly notes that there are “nine intellects” and “eight souls,” thereby providing a different number of celestial entities. Further research on the authenticity, chronology, and doctrinal content of these treatises is required to better understand how they relate to the shaykh al-raʾīs main works. I am grateful to Olga Lizzini for bringing these passages to my attention.

97 This is the case, for instance, with the eccentrics and epicycles, which Ibn Sīnā ascribes to Aristotle and which he manages to reconcile with other Aristotelian theories to fashion his own model. Another issue is why Ibn Sīnā does not connect the ‘first kinematic model’ with Ptolemy and especially with Planetary Hypotheses, from which some features are clearly derived, especially the idea that the planets govern their own motions as well as the motions of their adjacent orbs through psychological emissions.

98 At least some of these doctrinal variations may be due to the chronological order in which these works were composed, which may reflect different stages in Ibn Sīnā's philosophical development and could point to an evolution in his conceptualization of the specifics of celestial motion. Mabdaʾ, for instance, is an early work, excerpts of which were later used for the redaction of the Ilāhiyyāt of Shifāʾ and Najāt, whereas Ishārāt, which also treats of cosmological questions, was written at the end of Ibn Sīnā's life; see Gutas, Avicenna and the Aristotelian Tradition, pp. 30, 98–145. Indeed, it would be surprising if Ibn Sīnā held a consistent stance throughout his life with regard to these thorny cosmological issues. It is, of course, also possible that he never found the time to elaborate a fully coherent and systematic interpretation of these philosophical problems.

99 In holding that the eternity of celestial motion is due to an infinite intellectual power, and not merely to soul or nature, Ibn Sīnā is following an ancient tradition with both Aristotelian and Platonic precedents, such as Book Lambda 7 and Timaeus 34A respectively. This idea was then picked up and elaborated by some of the later commentators; see e.g., Simplicius, in Sorabji, The Philosophy of the Commentators, vol. 2, “Physics,” p. 52. The infinite power of the separate intellects, from which celestial motion is derived, is sometimes conceived of in Ibn Sīnā's cosmology as being emanated directly onto the celestial souls; see The Metaphysics of the Healing, p. 314,10-15, and Ishārāt, vols. 3–4, p. 608.

100 Ibn Sīnā, Mabdaʾ, pp. 58–61; id., The Metaphysics of the Healing, pp. 314,28-315-25.

101 Ibn Sīnā stresses this point on numerous occasions; see The Metaphysics of the Healing, pp. 313,9-11 and 34-36; 314,5-10; 324,34-37.

102 Motion is therefore not directly connected with the primary intention (al-qaṣd al-awwal) of the heavenly souls to imitate the intellects, but is rather a derivative effect; see The Metaphysics of the Healing, pp. 315,15-20 and 25-28; 316,6-10.

103 Ibn Sīnā, Mabdaʾ, pp. 54,16-18; 56,19-20; id., The Metaphysics of the Healing, pp. 309,16-17; 311,29–30; 315,28-30; id., Najāt, p. 621. Ibn Sīnā is careful to point out that it is motion that follows conception and not vice versa. Ṭūsī, Sharḥ al-Ishārāt, vols. 3-4, p. 608, uses a similar language and speaks of “the production of renewed states in the celestial soul” (ṣudūr al-aḥwāl al-mutajaddida fī al-nafs al-falakiyya).

104 Ibn Sīnā, The Metaphysics of the Healing, pp. 311,29–32; 312,8-13. In spite of this, it is somewhat unclear to what degree estimation and imagination are instrumental in producing the particular conceptions and intentions experienced by the souls.

105 For more information on the inner senses in Ibn Sīnā, see Black, D. L., “Estimation (wahm) in Avicenna: the logical and psychological dimensions,” Dialogue, 32 (1993): 219–58CrossRefGoogle Scholar; id., “Psychology: soul and intellect,” in Adamson, P. and Taylor, R. C. (eds.), Cambridge Companion to Arabic Philosophy (Cambridge, 2005), pp. 308–27Google Scholar; Hall, R. E., “Intellect, soul, and body in Ibn Sīnā: systematic synthesis and development of the Aristotelian, Neoplatonic, and Galenic theories,” in McGinnis, J. and Reisman, D. C. (eds.), Interpreting Avicenna: Science and Philosophy in Medieval Islam. Proceedings of the Second Conference of the Avicenna Study Group (Leiden/Boston, 2004), pp. 6286Google Scholar; id., “The wahm in Ibn Sīnā's psychology,” in Pacheco, M. C. and Merinhos, J. F. (eds.), Intellect and Imagination in Medieval Philosophy (Turnhout, 2006), pp. 533–49Google Scholar; Gutas, D., “Imagination and transcendental knowledge in Avicenna,” in J. E. Montgomery (ed.), Arabic Theology, Arabic Philosophy. From the Many to the One: Essays in Celebration of Richard M. Frank (Leuven/Paris/Dudley, 2006), pp. 337–55Google Scholar.

106 In The Metaphysics of the Healing, p. 325,12–13, Ibn Sīnā discusses conception (taṣawwur) and will (irāda) in connection with the orbs' imagination (takhayyul), two notions which are otherwise used to define the intellectual activity of the souls. Ibn Sīnā's inadequate explanations concerning the role of the inner senses in the celestial bodies mirror his equally problematic treatment of the inner senses in human beings, particularly with regard to their physical location; see Hall, “The wahm in Ibn Sīnā's psychology,” p. 547.

107 See Adamson, P., Al-Kindī (Oxford/New York, 2007), p. 184Google Scholar.

108 See Michot, La destinée de l'homme, pp. 111–12.

109 It should be said that some hints point to a different conclusion, i.e., that Ibn Sīnā would have argued in favor of the existence of the external senses; see for instance The Metaphysics of the Healing, p. 312,12: “its [i.e., the celestial soul's] apprehension [idrākāt] is by the body.” Is Ibn Sīnā referring here to the outer senses, or merely to the inner senses, which, while usually connected with the bodily senses, are nevertheless turned in this case toward the higher rational faculty?

110 This striking analogy is made by Ibn Sīnā in Ishārāt, vols. 3-4, p. 864; in K. al-Ḥudūd, p. 16 of the Arabic text; in his treatise on astrology, and in Taʿlīqāt (for the latter two sources, see Ibn Sīnā, Réfutation de l'astrologie, pp. 37/134–5 and note 1, p. 135). Naturally, it does not refer to the vegetative faculties of nutrition, reproduction, and growth, which are entirely lacking in the case of the celestial bodies, nor does it refer to sense perception, which the orbs presumably also lack. Rather, it would seem that Ibn Sīnā has in mind the rational, imaginative, and estimative faculties, which are common to both human beings and the heavens.

111 Ibn Sīnā, Ishārāt, vols. 3–4, p. 864. It is unclear how strictly Ibn Sīnā wants the reader to construe these analogies. In light of the following discussion, it seems nevertheless that they adequately represent the process of celestial motion. At any rate, these passages show the important place that analogy occupies in Ibn Sīnā's cosmological approach and indicate that the physical investigation of sublunary nature may be used to infer certain properties about the superlunary existents. They also point to the formal and conceptual parallels that exist between Ibn Sīnā's psychological and cosmological theories.

112 Ibn Sīnā, The Metaphysics of the Healing, p. 332,22–24.

113 Ibn Sīnā, The Metaphysics of the Healing, p. 308,20 ff. For the various technical senses of maʿnā in Ibn Sīnā's psychology, see Black “Estimation.” An intention (maʿnā) is usually itself non-material, albeit closely connected with the faculty of estimation and thus with the sensual powers of the body. In the case of the celestial souls, however, maʿnā is an ambiguous concept, since it cannot be easily connected with the inner senses.

114 For a discussion of the concept of mayl in Ibn Sīnā's dynamics, see Hasnawi, A. “La dynamique d'Ibn Sīnā: la notion d'inclination (mayl),” in Jolivet, J. and Rashed, R. (eds.), Études sur Avicenne (Paris, 1984), pp. 103–23Google Scholar. Hasnawi aptly describes mayl as an intermediary reality between the mover and its motion. In the case of celestial motion, mayl is neither the motion itself nor the motive power, but an intermediary stage in the realization of motion, which combines with the psychological activity of the celestial bodies and enables the transmission of the motive powers to the corporeal part of the orbs; see Mabdaʾ, p. 54. The term mayl appears in Alexander's Mabādiʾ, but it does not seem to play the same role there and is not explicitly connected with the activity of the celestial souls; see Genequand, Alexander of Aphrodisias on the Cosmos, pp. 46–7, 52–3. According to Genequand, pp. 6–7, and note 11, Alexander applies it chiefly to inanimate existents. Cf. Pines, S., “Omne quod movetur necesse est ab aliquo moveri: A refutation of Galen by Alexander of Aphrodisias and the theory of motion,” Isis, 52 (1960): 2154, pp. 44–7CrossRefGoogle Scholar, who discusses the relation between inclination, nature, and the celestial souls in Alexander. Inclination also plays an important role in Philoponus' works, whose articulation of this concept together with the related concept of impetus had a profound influence in Islam; see Zimmermann, F. W., “Philoponus' impetus theory in the Arabic tradition,” in Sorabji, R. (ed.), Philoponus and the Rejection of Aristotelian Science (Ithaca/New York, 1987), pp. 121–30Google Scholar; R. Wisnovsky, “Yaḥyā al-Naḥwī,” in EI 2.

115 Ibn Sīnā, The Metaphysics of the Healing, p. 308; cf. Ishārāt, vol. 2, pp. 413–14. For insight into some of the late-antique views on these concepts, see Sorabji, The Philosophy of the Commentators, vol. 2, “Physics,” pp. 56–7, 329, 344–8.

116 Pines, “Omne quod movetur,” pp. 44–7; Genequand, Alexander of Aphrodisias on the Cosmos, pp. 52–5; Simplicius on Alexander in Sorabji, The Philosophy of the Commentators, vol. 2, “Physics,” pp. 344–8.

117 Ibn Sīnā, The Metaphysics of the Healing, p. 308,33–35.

118 See notably Hasnawi, “Fayḍ,” pp. 966–72; Janssens, J., “Creation and emanation in Ibn Sīnā,” Documenti e studi sulla tradizione filosofica medievale, 8 (1997): 455–77Google Scholar; Wisnovsky, “Final and efficient causality”; and Lizzini, O., Fluxus (fayḍ): Indagine sui fondamenti della metafisica e della fisica di Avicenna (Ibn Sīnā, m. 427/1037) (Bari, 2010)Google Scholar.

119 Ibn Sīnā, Mabdaʾ, p. 28.

120 Ibn Sīnā, Mabdaʾ, p. 54.

121 Hasnawi, “La dynamique d'Ibn Sīnā,” p. 104.

122 Ibn Sīnā, Najāt, p. 632 ; cf. id., The Metaphysics of the Healing, p. 316,6–7.

123 Ibn Sīnā, Ishārāt, vols. 3-4, p. 608. Ṭūsī in his Sharḥ al-Ishārāt, vol. 2, pp. 413, 418, follows Ibn Sīnā closely on this point and comments that the celestial motions come out of (ṣādira ʿan) the celestial soul. For a detailed analysis of the meaning of inbiʿāth in Ibn Sīnā, see Lizzini, Fluxus (fayḍ), Appendix I.1.3; cf. De Smet, La quiétude de l'intellect, pp. 197 ff., 210–13, for its meaning in al-Kirmānī's works. Interestingly, the term inbiʿāth and the recurring analogy Ibn Sīna makes between the celestial bodies and the sublunary bodies bring to mind some of the excerpts of Planetary Hypotheses already discussed. It was shown, however, that Ibn Sīnā disagrees with Ptolemy on many other crucial points, so that their theories of emanating powers ultimately play a different role in their cosmologies and are integrated in a different physical-metaphysical framework.

124 Ibn Sīnā, Najāt, p. 303.

125 Ibn Sīnā, R. fī al-jawhar al-nafīs, in Majmūʿāt al-rasāʾil, pp. 256–79, ed. by Muḥy al-Dīn Ṣabrī al-Kurdī (Cairo, 1328/1910), p. 278. These passages should be read and interpreted in light of Alexander of Aphrodisias' De providentia, which also displays a theory of emanating celestial powers (sing. quwwa munbaʿitha) on the sublunary world; see Alexander of Aphrodisias, Traité de la providence = Peri pronoias, introduction, édition et traduction de Pierre Thillet (Lagrasse, 2003), p. 10/105. For further insight into this issue, see Fazzo, S. and Wiesner, H., “Alexander of Aphrodisias in the Kindī-circle and in al-Kindī's cosmology,” Arabic Sciences and Philosophy, 3 (1993): 119–53CrossRefGoogle Scholar.

126 Ibn Sīnā, Ishārāt, vol. 2, pp. 407, 412; id., Shifāʾ, Ṭabīʿiyyāt, vol. 2, part 6, al-Nafs, p. 5.

127 Ibn Sīnā, Najāt, p. 633. For Ibn Sīnā, taʾthīr usually expresses the generation of an act or movement out of a potentiality; see Lizzini, Fluxus (fayḍ), Appendix I.1.7.

128 Ibn Sīnā, The Metaphysics of the Healing, p. 316, 5–20.

129 Ibn Sīnā, K. al-Ḥayawān, Shifāʾ, p. 236, l. 6. The term munbaʿith also appears frequently in this same passage to explain how the signals are transmitted from the brain throughout the nervous system; see e.g., p. 236,10–13.

130 Hasnawi, “Fayḍ,” p. 966.

131 See the references given in footnotes 110 and 111. This analogy between heavenly and animal motion is taken up and expanded by Ṭūsī in his commentary on Ishārāt, vol. 3-4, pp. 618–19. Can this psychological account of celestial motion have been influenced by Galenic physical theories? Or did Ibn Sīnā develop them from his readings of Aristotle's physical treatises, such as De motu animalium? These questions require a deeper investigation into the Galen Arabus and into Ibn Sīnā's physical and zoological treatises, which unfortunately cannot be provided here. At any rate, I have so far emphasized the parallels between Ibn Sīnā's sublunary and superlunary kinematics, thereby suggesting an analogical approach to the problem of celestial motion, which would accordingly find its point of departure in physical observations. But it is possible that the inspiration to use emanationist or causative vocabulary in the context of celestial motion originated from a completely different angle, namely, Ibn Sīnā's metaphysics of causation and emanation. In this case, Ibn Sīnā's theories with respect to celestial motion would be a transposition to a lesser ontic level of metaphysical theories which he had originally applied to the First Cause and the separate intellects and which he secondarily chose to apply in a modified form to the lower entities of his metaphysics, including the celestial souls, in order to explain how their motions occur. Just as the world is caused through the fayḍ of God, one may say that celestial motion is caused by the fayḍ of the separate intellects on the celestial souls, and of the latter on the celestial bodies. The texts which contain these emanationist theories and terminology, such as K. fī maḥḍ al-khayr and Theology of Aristotle, use them in the context of creation and apply them to the First Cause and the intellects, but not to physical or celestial motion. Ibn Sīnā's innovation would thus have been to apply this causative or emanationist terminology to celestial motion specifically and connect it with the causality of the higher, immaterial principles. But given Ibn Sīnā's very explicit analogies between sublunary and superlunary motion, I am more inclined to think that the theoretical framework and terminology he applies to the heavens are inspired by his theories of animal motion and human psychology. It is probably these fields that provided him with the main model and elements to articulate his theory of celestial kinematics.

132 This elaboration was made possible by Ibn Sīnā's historical position at the receiving end of the late-antique (chiefly Neoplatonic) commentatorial tradition. On procession, reversion, and causality in Ibn Sīnā's metaphysics and his debt to the Greek commentatorial tradition on these issues, see Wisnovsky, Avicenna's Metaphysics in Context, pp. 183–95; id., “Final and efficient causality”; for the Greek background, see the relevant articles in Sorabji, R. (ed.), Aristotle Transformed (Ithaca, 1990)Google Scholar; and Rosemann, P. W., Omne Agens Agit Sibi Simile: A “Repetition” of Scholastic Metaphysics (Leuven, 1996)Google Scholar.

133 Like Ptolemy, Ibn Sīnā expresses some hesitation concerning the best planetary model to be used to explain the sun's motion, which may or may not include an epicycle; see his own comments in Lucchetta, “Le dieci questioni,” p. 127.

134 It is perhaps in this sense that one should interpret Ibn Sīnā's statement in Najāt, p. 617, that the heaven as a whole is an “obedient animal” (ḥayawān muṭīʿ).

135 This of course explains why it is necessary that each celestial body be ensouled. If each celestial body – epicycle, eccentric, planets, etc. – has a separate principle corresponding to it, then it per force must be ensouled in order to be able to contemplate this principle and thus for motion to take place. One of the implications of the ‘first kinematic model’ is that by making the planetary soul the sole responsible for moving the various orbs of its system, the ensoulment of the eccentrics and epicycles becomes superfluous, as these can be conceived of as mere bodies, analogous to the limbs or parts of an animal moved by the soul located in the brain or heart.

136 For Ibn Sīnā's general attitude in this regard, see Gutas, Avicenna and the Aristotelian Tradition.

137 That Ibn Sīnā recognized the intrinsic difficulty of explaining celestial motion is suggested not only by his hypothetical tone in many of the passages discussed in this article, but also by his repeated assertion that the exact mechanisms underpinning celestial motion, and especially the will of the celestial souls, is a matter of wonder or “mystery” (sirr); see Ibn Sīnā, Ishārāt, vol. 2, p. 417; cf. id., The Metaphysics of the Healing, p. 325,2–7.

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