The groundbreaking physics of Averroës

Studies in History and Philosophy of Science 42 (2011) 210–214 Contents lists available at ScienceDirect Studies in History and Philosophy of Science journal homepage: www.elsevier.com/locate/shpsa Essay Review The groundbreaking physics of Averroës Nader El-Bizri Institute of Ismaili Studies, 210 Euston Road, London NW1 2DA, UK When citing this paper, please use the full journal title Studies in History and Philosophy of Science Averroes’ Physics: A Turning point in medieval natural philosophy, Ruth Glasner. Oxford University Press, Oxford (2009). x+229 pp., £37.50-US$75.00 hardback, ISBN 978-0-19-956773-7. This essay focuses on Averroës’ physics, by way of also reviewing Ruth Glasner’s recent book on his natural philosophy (Glasner, 2009). This line of inquiry examines the unfolding of Averroës’ philosophical and scientific thinking, in the context of his scrupulous commentaries on Aristotle’s Physics, and his critical reappraisal of the exegetical efforts of his predecessors in interpreting this foundational Aristotelian opus. Prior to investigating this topic, and assessing the particulars of Glasner’s analysis, it is perhaps pertinent to succinctly introduce ‘Averroës’, and to present a concise account of his principal oeuvres.  al-Walı̄d Muhammad ibn Ahmad His full name in Arabic is: Abu ibn Rushd; commonly known as: ‘Ibn Rushd’, and in Latinate renderings as: ‘Averroës’. He was born in Cordoba (in Andalusia) in 1126 CE, and died in Marrakesh (in Morocco) in 1198 CE. Our illustrious Arab-Andalusian polymath was a philosopher, a jurist (Sunni, Mālikı̄ jurisprudence) and a renowned physician (Renan, 1882, pp. 435–465; Urvoy, 1991, pp. 29–37). He played a decisive role in defending Greek philosophy against its critics in the Muslim world; particularly in response to the scepticism of the Ash’arite dialecti n; the exponents of the Kalām tradical theologians (al-mutakallimu  al-Hasan al-Ash’arı̄), and tion of the 10th century Imam Abu principally in refuting the doubts that were raised by the Imam  Hāmid al-Ghazālı̄ (d. 1111 CE) concerning the ‘rationality’ of Abu the philosophers. Averroës endeavoured also to ‘rehabilitate’ Aristotle’s corpus, by way of analytical and critical reconstructive commentaries, which aimed at removing what he judged as being ‘alien’ interpolations and interpretations that deviated from the ‘original’ Aristotelian texts through the agency of ‘confused’ past exegetes and ancient hermeneutists. Averroës was mentored by various prominent scholars in Anda Bakr ibn Tufayl (Lat. Abublusia of the calibre of the polymath Abu acer Aben Tofail, the Philosophus Autodidactus; d. ca. 1185 CE), the E-mail address: [email protected] 0039-3681/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.shpsa.2010.11.009  Marwān ibn Zuhr (Lat. Abumeron physician and surgeon Abu  Bakr ibn Bājja Avenzoar; d. ca. 1161 CE), and the philosopher Abu (Lat. Avempace; d. ca. 1139/43 CE). Averroism exercised some  sā ibn Maymu  n (Moses influence in shaping the thought of Mu Maimonides; d. 1204 CE), and it dialectically impacted the intellectual tradition of St. Thomas Aquinas (d. 1274 CE). Averroës’ philosophical works were perhaps more widely disseminated and adaptively assimilated within European mediaeval scholastic circles than in the Muslim world (Renan, 1882, pp. 177–180, 184–192, 236–245); even though, the integration of ‘Averroism’ within Latin scholarship was eventually ‘forbidden’ under the ‘Condemnation of 1277’ (namely, the prohibition of numerous key philosophical theses under the office of the Bishop of Paris, Étienne Tempier [Stéphane d’Orléans]). Figures like Sygerius de Brabantia, Boethius of Dacia, Bernier de Nivelles, and Gossuin de la Chapelle were condemned in Paris for their ‘Averroistic heresies’; and Dante Alighieri was posthumously criticised for his tacit associations with Averroism, mainly in reference to his De monarchia (with hints also to honouring Averroës in the Divina commedia). Renaissance artists did not fail to recognise Averroës’ contributions to knowledge, depicting his ‘imagined’ portrait alongside the finest masters of classical traditions in science and philosophy (like his pictorial portrayal in one of the quattrocento murals by Andrea di Bonaiuto, in Florence, or the speculation that he was even depicted in the legendary cinquecento fresco of Raffaello Sanzio, La scuola di Atene, in the Stanza della Segnatura of the Vatican Apostolic palace; reclining therein behind the figures of Pythagoras, Hypatia and Boethius?). Averroës was recognised in Europe, as early as the thirteenth century, as the ‘commentator’ par excellence on Aristotle’s oeuvres; contributing to the ‘rediscovery’ of ‘the Greek Master’, which was instrumental to the development of Latin Scholasticism, with the eventual impact of its intellectual impetus on scholarship in the Renaissance. Although many Arabic critical editions of Averroës’ masterpieces have been published, they nonetheless constitute a relatively small N. El-Bizri / Studies in History and Philosophy of Science 42 (2011) 210–214 portion of what is extant of his textual legacy and preserved manuscripts. Of his texts that are available in Arabic, we ought to mention his magnum opus, the Tahāfut al-tahāfut (The Incoherence of ‘the Incoherence’; Destructio Destructiones; Ibn Rushd, 1950, 1954, 1998), which he composed in the form of a critical refutation of al-Ghazālı̄’s Tahāfut al-falāsifa: (The Incoherence of the Philosophers; Destructio Philosophorum; al-Ghazālı̄, 1997). Several of Averroës’ works are extant in Arabic, including his Talkı̄s kitāb al-jadal (Middle Commentary on Aristotle’s Topics), Fasl al-maqāl mā bayn al-sharı̄’a wa-al-falsafa min ittisāl (The Decisive Discourse on the Connection between Religious Law and Philosophy; Ibn Rushd, 1976), the Kash manāhij al-adilla fı̄ ‘aqā’id al-milla (Disclosing the systems of proof in the beliefs of co-religionists; extracts in Ibn Rushd,  rı̄ fı̄ usu  l al-fiqh (On the essentials of the principles of 1976), al-Daru jurisprudence), and Bidāyat al-mujtahid wa nihāyat al-muqtasid (prolegomena of the jurist and the seeker’s ends). Averroës produced a whole constellation of commentaries on Aristotle’s works, including the Physics (al-Tabı̄’iyyāt; Fann al-samā’ al-tabı̄’ı̄). He composed exegetical and critical tracts on De caelo (al-‘ālam), De generatione et corruptione (al-kawn wa-al-fasād), Meteorologica (al-āthār al-‘ulwiyya), De animalibus (al-hayawān),  s), De anima (kitāb al-nafs), Parva naturalia (al-hass wa-al-mahsu Metaphysica (mā ba’d al-tabı̄’a), Moralia Nicomachea exposition . . . along with recensions on the Organon, Topica, Categoriae, Isagoge, Peri Hermeneias, Analytica priora et posteriora, in addition to epitomes on Plato’s Republic and Ptolemy’s Almagest. Moreover, he established manuscripts in Galenic medicine, including his encyclopaedic compendium: Kitāb al-Kulliyāt fı̄ al-tibb (Colliget Averrois), along with a commentary on the monumental medical  n fı̄ al-tibb opus of Avicenna (Ibn Sı̄nā; d. 1037 CE), the Kitāb al-Qānu (The Canon of Medicine). Michael Scotus (d. ca. 1232 CE) translated some of Averroës’ works from Arabic into Latin, while Jacob Anatoli (d. ca. 1256 CE) translated several of his treatises from Arabic into Hebrew (including the middle commentaries on Aristotle’s Logic). Subsequently, the Hebrew renditions were translated into Latin by Jacob Mantino (d. ca. 1549 CE) and Abraham de Balmes (d. ca. 1523). The fullest collection of his works that is available in Latin is preserved within the 16th century multivolume Venice edition of Aristotle’s works: Aristotelis opera cum Averrois [Cordubensis] commentariis (Venetiis, 1562–1574). It is hoped that the epigrammatic overview of Averroës’ biobibliography (Renan, 1882; Urvoy, 1991), which has been laconically noted above, would have offered a wide-ranging perspective on the extent and diversity of his contributions to philosophical and scientific knowledge. Nevertheless, we ought to turn at this junction of this present essay towards a consideration of his commentaries on Aristotle’s Physics, which constitute the pivotal theme of Glasner’s book on his ‘natural philosophy’ that is under review hereinafter. Averroës’ commentaries on Aristotle’s Physics can be classified in terms of three genres: a—The ‘Short Commentary’ (‘Epitome’ or ‘overview’; jāmi’), b—The ‘Middle Commentary’ (‘Commentarium medium’ or ‘Synoptic analysis’; talkhı̄s), and c—The ‘Long Commentary’ (‘Commentarium magnum’ or ‘word-by-word exegesis and critical recension’; sharh, or tafsı̄r). Glasner offers an informative and novel interpretation of Averroës’ natural philosophy, based on detailed analyses of the threefold variety of his commentaries on Aristotle’s Physics; including extant manuscripts of Hebrew and Latin renditions of some of his original tracts that have been lost in their Arabic versions. Glasner shows how Averroës reworked and refined various aspects of his conception of the fundamental notions of physics, including the analysis of the nature of corporeal reality and the principle of motion. She examines the architectonics of his systematisation of natural philosophy, which she refers to as ‘Aristotelian atomism’; 211 revealing the manner by which his thoughtful exegesis of Aristotle’s Physics resulted in an innovative whole novel physical theory. The faithful didactic ‘commentator’ on Aristotle appears again as an original philosopher in his own right; with Averroism being perhaps as influential as Avicennism (the legacy of Avicenna [Ibn Sı̄nā]), and on par with Aristotelianism in the mediaeval epoch and up till the Renaissance. Glasner traces back to Averroës a rich assemblage of key philosophical and scientific notions that were (erroneously) attributed to mediaeval European scholastic commentators. She does not simply show that these later developments within European history of science and philosophy merely originated in their rudimentary forms from interpretive appropriations of Averroës’ tradition, but rather that they were already comprehensively developed by him in a unified and coherent ‘physical system’, which was subsequently transmitted into the mediaeval intellectual European milieu. Glasner argues that Averroës’ physics was ‘atomistic’, while being at the same time rooted in the Aristotelian tradition. By way of detailed analyses of the conceptual subtleties of Averroës’ commentaries, she scrupulously reveals how his nuanced exegetical adjustments allowed him to resolve the principal internal inconsistencies within Aristotle’s Physics, and the elucidation of its ambiguities through novel philosophical pathways in thinking. His outlook resulted in the development of an ‘indeterminist natural philosophy’ that was soundly ‘scientific’, according to the epistemic standards of his age, instead of being speculative in its theoretical constructs. The association of ‘atomist’ notions with Aristotelian leitmotifs seems to be paradoxical, given their prima facie ‘incommensurability’. Averroës was aware of this anomaly and its implied antinomies; albeit, he capitalised carefully on reforming selected conceptual elements, which he critically judged as being ‘foreign’ to Aristotle’s thought, in order to devise novel directions in rethinking natural philosophy on sound scientific grounds. Averroës was principally critical of ‘non-Aristotelian notions’ that were ‘misleadingly’ associated with Aristotle’s corpus through the agency of Neo-Platonist commentaries. Averroës endeavoured to identify and deconstruct the extraneous additions to Aristotle’s lemmas and maxims, in view of presenting a more faithful rendering of the Aristotelian text, while removing its incongruities, elucidating its ambivalences, and opening it up to new epistemic horizons. Averroës was critically disposed towards the 6th century Christian grammarian John Philoponus, and the falāsifa of Islam,  Nasr al-Fārābı̄ (Alpharabius; d. ca. 950 CE) and Ibn Sı̄nā like Abu (Avicenna; d. 1037 CE), in terms of their (Neo-Platonised) ‘commentaries’ on Aristotle’s corpus. In contrast, Averroës praised the ‘conscientious’ approach of the 2nd/3rd century Peripatetic commentator Alexander of Aphrodisias (Glasner, 2009, pp. 22–24, 56). Nonetheless, the ‘internal dialectical tensions’ within Aristotle’s Physics facilitated Averroës’ inventive interventions in terms of reconciling concepts that seemed (at first glance) to be irreconcilable. Consequently he advanced an original physical theory of his own, which Glasner designates by the appellation: ‘Aristotelian atomism’. This ‘turning point in mediaeval natural philosophy’ was also associated with Averroës’ ‘minima naturalia’ (‘minimal parts’) and ‘forma fluens’ (‘form of motion’) theses, which exercised profound influences on history of science and philosophy, including early-modern investigations of matter and motion (Glasner, 2009, pp. 2–5; Maier, 1958; Murdoch, 2001). In analysing this epistemological and historical development, Glasner focuses on three ‘turning-point’ revision patterns in Averroës writings (Glasner, 2009, pp. 57–175), which she studies ‘diachronically’ in view of gasping the ‘chronological order’ of the unfolding of his distinct new model of natural philosophy and unique physical theory (Glasner, 2009, p. 9). 212 N. El-Bizri / Studies in History and Philosophy of Science 42 (2011) 210–214 Glasner offers a detailed description of the extant manuscripts of Averroës’ commentaries on Aristotle’s Physics, which he based on the 9th century Arabic translation of this Aristotelian masterpiece by Ishāq ibn Hunayn. Glasner supports her analytics with informative tables, indices, cataloguing research-tools, along with the chronological dating of manuscripts and the philological elucidation of their particulars, in addition to presenting synopses of their contents (Glasner, 2009, pp. 10–21). For instance, Averroës’ ‘Short Commentary on the Physics’ (composed around 1159 CE) is extant in Arabic, and it has been critically edited and translated by Josep Puig Montada, based on a Cairo manuscript and a Madrid one, along with other fragments from a 16th century Hebrew rendition (Riva di Trento, 1559). As for Averroës’ ‘Middle Commentary on the Physics’ (written in 1170 CE), it survives in an outline form in the original Arabic, with two Hebrew adaptations, and one additional manuscript translated from a Hebrew version into Latin (referred to as a ‘paraphrasis’, but being more accurately an ‘exegesis’). Moreover, the ‘Long Commentary on the Physics’ (compiled around 1186 CE) is extant through a 13th century Latin version, which has been attributed to the hand of Michael Scotus, and it also exists in a 14th century manuscript of a Hebrew rendition. Averroës subjected his commentaries on Aristotle’s Physics to multiple modifications, revisions, and, at times, entire rewritings. Glasner describes these variants in detail (mainly through extant Hebrew and Latin manuscripts), while assessing their potential implications in terms of understanding the unfolding of Averroës’ thought (Glasner, 2009, pp. 28–40). Although his texts existed in sequences of variegated redactions and recensions (tanqı̄hāt), Glasner’s analysis would have been contingent upon the properties of the manuscripts, their dating, stemma codicum, channels of transmission, the interpolations of copyists and scholiasts, and the deviations from the original that result from the processes of the ‘metamorphosis’ of meanings by way of ‘translation’. Accordingly, the picture she depicts cannot circumstantially be definitive; and one has to guardedly accept her assertion that ‘most of the differences’ in the various versions of the manuscripts of his commentaries ‘undoubtedly [italicised emphasis mine] go back to Averroës himself’ (Glasner, 2009, p. 35). Averroës probingly examined the structures of syllogism deployed in the logical formalisation of natural philosophy, and in relation to selected propositions in Physics I.4, or III.5 (on the finitude of first principles, of body and number; Glasner, 2009, pp. 48–52). His effort in rethinking Aristotle’s Physics was undertaken in terms of theoretical philosophising instead of relying on geometrical demonstration as several mathematicians of Islamic civilisation did since the 10th century. We ought to mention in this context polymaths and philomaths like the astronomer and  Sahl Wayjan ibn Rustam al-Qu  hı̄ (d. ca. 1000 geometrician Abu CE), and more significantly, the great optician and geometrician al-Hasan ibn al-Haytham (Alhazen, d. ca. 1041 CE). Both endeavoured to ‘mathematise’ physics and its notions (time, space, and  hı̄ demonstrated in a geometrical opusmotion). For instance, al-Qu culum that ‘an infinite motion is possible in a finite time’ in refutation of Aristotle’s thesis in Physics VII.7; he also showed how ‘rest occurs between two contrary motions, whether they were straight or followed an arc’, in view of rejecting Aristotle’s thesis in Physics VIII.8 (Rashed, 2005, pp. 975–987). Similarly, Ibn al-Haytham refuted the Aristotelian definition of place (topos), as a boundary surface of envelopment and containment, in Physics IV.5 (D.5, 212a 6–7, 20–21), in view of presenting his own ‘geometrical conception’ of place (al-makān) as a ‘postulated void’ (khalā’ mutakhayyal) qua ‘spatial extension’, in his mathematical treatise: Qawl fı̄ al-makān (Discourse on Place; El-Bizri, 2007, pp. 57–80). This line of geometrical demonstration, which aimed at reappraising Aristotle’s Physics, and deconstructing it a fortiori, seems to have escaped Glasner’s direct attention, even though it warrants analysis given its epistemic bearings on understanding the critique of ‘natural philosophy’ by Averroës’ predecessors in history of the exact sciences and mathematics in Islamic civilisation. Glasner focuses her probing analysis à fond on Averroës’ rethinking of the notion of ‘motion’ (kinēsis; al-haraka) in response to Books VI, VII, VIII (Z, Y, H) of Aristotle’s Physics (Ross ed. 1936). This endeavour can be conceptually summarised in terms of the following arguments and associated theses: 1—Aristotle’s ‘divisibility’ argument (Physics VI.4, 234b 10–20; Ross, 1936): ‘everything that is moved must be divisible’, is developed by Averroës into a ‘breakdown of motion’ thesis (Glasner, 2009, pp. 109–140); 2—Aristotle’s ‘moving-agency’ argument (Physics VII.1, 241b 34 – 242a 49): ‘every mobile must be moved by something’, is developed by Averroës into a ‘breakdown of the physical body’ thesis (Glasner, 2009, pp. 141–171); 3—Aristotle’s ‘succession’ argument (Physics VIII.1, 251a 8 – 251b 10): ‘before any motion, there must have been a previous motion’, is developed by Averroës into a ‘breakdown of determinism’ thesis (Glasner, 2009, pp. 62–108). Glasner presents these arguments in a different order; starting with book VIII, followed by book VI and then by book VII, in a sequence that corresponds with chapters 6, 7 and 8 of her book (with chapter 8 being wrongly titled in its running header, as a study on ‘Physics III’, [perhaps by way of a typographical erratum], while being actually focused in its contents on ‘Physics VII’). Following Glasner’s sequence, we note that Aristotle’s ‘succession’ argument in Physics VIII underpinned the mediaeval cosmological doctrine of ‘the eternity of the world’, with its implied determinism (Glasner, 2009, p. 62). In response to the serious polemics that surrounded this ontological-cosmological thesis, which was advocated by most philosophers in Islam (al-falāsifa),  n), Averroës and rejected by Muslim theologians (al-mutakallimu aimed at establishing a scientifically oriented natural philosophical thesis of ‘indeterminism’, which brought him closer to the theological ‘physical theories of atomism’ (the ‘physics’ of the exponents of Kalām). Averroës aimed at reappraising the Aristotelian ‘law of association’, namely, that: ‘entities which are contiguous in space and time (hence in contact or close proximity) are readily associated as a series’. This ‘association’ principle connects with the idea of ‘succession’ (ephexēs; yatlu or tilāwa), which was investigated in its turn within classical traditions in physics and geometry, and, specifically, in terms of their bearings on the conception of ‘motion’. Determinism is implied through the ‘rational’ focus on ‘the necessary connection between causes and their effects’, and not simply in terms of affirming the ‘principle of sequence’. The influential theologian al-Ghazālı̄ raised doubts regarding the ‘necessary’ character of causation in ‘Discussion 17’ of the ‘Physical Sciences’ part of his Incoherence of the Philosophers (alGhazālı̄, 1997, pp. 170–181); consequently, breaking the deterministic chain of ‘naturalised fatalism’ by way of scepticism regarding the justification of induction (perhaps the call for certainty invited scepticism!). Based on atomism in the Kalām tradition, the atom is described as a ‘substance’ (jawhar) that is ‘a part that cannot be partitioned [or divided]’ (juz’ lā yatajazza’). Atoms can be aggregated or segregated due to accidental states that occur to them (hence, when in aggregation, they constitute what appears as being a unified given physical body). Supported by ‘atomist physics’ alGhazālı̄ argued that: ‘the connection, between what is habitually believed to be a cause (sabab), and what is habitually believed to  rı̄)’ . . . ‘neither the be an effect (musabbab), is not necessary (daru affirmation of the one entails an affirmation of the other, nor the negation of the one entails a negation of the other’ (al-Ghazālı̄, 1997, p. 170). We cannot therefore talk about necessity with regard to nature, rather its ‘laws’ are deeply entrenched ‘habits qua customs’, inspired by divine volition (El-Bizri, 2008, pp. 121–140). This ‘occasionalist’ outlook affirms that atoms are N. El-Bizri / Studies in History and Philosophy of Science 42 (2011) 210–214 created ex nihilo, and that their aggregation or segregation is accidental and dependent on what is external to them. If we bracket ‘occasionalism’, the picture we depicted above carries some ontological resonances with the metaphysics of Avicenna (Ibn Sı̄nā) and the distinction he established between  d; existentia). Conessence (māhiyya; essentia) and existence (wuju tingents become actualised and brought into existence by what is external to their essences. A contingent (mumkin) has borrowed existence, in the sense that it is neither necessary nor impossible for it to be or not to be. The contingent is ontologically neutral. ‘In-itself’ (bi-dhātihi), the contingent is in essence a mere potentiality to be, which becomes ‘a necessary existent due to what is  d bi-ghayrihi), by way of an external other than itself’ (wājib al-wuju existential cause that brings it from potentiality (al-quwwa) into actuality (al-fi’l; El-Bizri, 2001, pp. 753–778). Avicenna’s ontology rests on the aetiological affirmation of causation unlike the ‘ontotheological’ doctrine advocated by the theosophists of Kalām. Averroës subscribed also to an affirmation of causality in ‘rational’ scientific inquiry and explanation, and he refuted al-Ghazālı̄’s doubts regarding causation and the justification of induction. He even described al-Ghazālı̄’s scepticism as mere ‘sophistry’ and as being indicative of ‘irrationality’ (Ibn Rushd, 1998, pp. 505–507). And yet, Averroës avoided the implied determinism that is entailed by the principle of causation. He even advocated a conception of ‘contiguous motion’ that tacitly echoed, in abstract terms, what al-Ghazālı̄ suggested by way of rethinking the connection between causes and effects in terms of ‘contiguity’ as ‘concinnity’ (al-tasāwuq; concinnitas). In doubting the veridical conditions of empirical observational data, when used in justifying causation, al-Ghazālı̄ argued that: ‘being with [‘ind] something does not prove existing by [bih] it’ (al-Ghazālı̄, 1997, pp. 170–171). This phenomenon is used in doubting a posteriori knowledge, without affirming a pure mode of knowing a priori. The ‘necessary connection between cause and effect’ is reduced into a state of association of the order of ‘being with’. This outlook against aetiology resonates indirectly with Averroës’ ‘Sub-Lunar physics’, which he grounded on the notion of ‘contiguity’ (shafā’a) in ‘succession’, in view of eschewing the idea of ‘continuity’. Perhaps the constructs that Averroës attempted to refute in al-Ghazālı̄’s arguments were readapted, in abstract conceptual terms, to serve his own theoretical objectives! This question was not considered by Glasner, despite its profound implications in understanding the conceptual ‘osmosis’ between theology, philosophy and science in Islam. This theoretical matter is also congruent with Averroës’ appropriation of ‘atomist’ notions within his natural philosophy, particularly when studying physical phenomena within the terrestrial sphere; namely, in the region below the sphere of the Moon (Glasner, 2009, pp. 68–69). Averroës held that two successive entities are ‘contiguous’ (ekhomenon; shāfi’) if they are touching. Accordingly, and in line with Aristotle’s Physics V.2, it can be stated that: ‘change can be consequent upon change only accidentally’ (Glasner, 2009, p. 72). In endeavouring to overcome ‘philosophised determinism’ and ‘theologised occasionalism’, in cosmology and ontology, Averroës examined the various degrees in measuring ‘proximity’ in relation to the notions of ‘succession’, ‘contiguity’ and ‘continuity’. Averroës realised that the Stoics did not distinguish ‘contiguity’ from ‘continuity’ in their radical determinism, or that Kalām theologians did not differentiate ‘contiguity’ from ‘succession’ in their orthodox occasionalism (Glasner, pp. 64, 75, 77–78). Averroës argued that: if the motion that is assumed to be the first must be preceded by another in terms of ‘succession’, this does not entail that the second motion is ‘contiguous’ to the one preceding it, but only that it succeeds it. Perhaps this account distanced him from al-Ghazālı̄’s account of ‘concinnity’ (al-tasāwuq) in reference to causality; a question that evidently merits further research, in 213 view of possibly revealing with more clarity Averroës’ arrièrepensée. Based on Averroës’ view, there is a certain ‘time of rest’ between the first and the second motion; and it is within this temporal lapse that the possible (qua contingent [neither necessary nor impossible]) can be. However, Averroës seems to be drawn nearer, in this regard, to the ‘leap thesis’ (al-tafra) that is attributed to the 9th century theologian Ibrāhı̄m ibn Sayyār al-Nazzām (van Ess, 1967, pp. 170–201), which, in line with Kalām, dismissed the ideas of plenum and continuum in the universe, while at the same time advancing a novel thesis about spatial-temporal leaps in motion that give the ‘semblance of continuity’ in movement and change. This perspective on motion was not investigated by Glasner, even though it deserves elucidation, given the richness of the ‘physical’ theories of the theologians in Islam, and the impact they indirectly had in dialectically shaping ‘natural philosophy’.  b, wājib) is The Aristotelian ‘metaphysics of necessity’ (wuju translated by Averroës into a thesis of ‘continuity in motion’, with regard to the ‘Physics’ of the Supra-Lunar celestial realm and its perpetuity, while the Kalām ‘theology of contingency’ (imkān, mumkin) is interpreted by him in terms of affirming the thesis of ‘contiguity in motion’ with respect to the ‘physics’ of the Sub-Lunar terrestrial region and its corruptibility. Averroës’ idiom is reminiscent of the metaphysical vocabulary of Avicenna (Ibn Sı̄nā), with regard to  b), impossibility (imtithe ontological modalities of necessity (wuju nā’) and contingency qua possibility (imkān), even though Glasner does not refer to this matter to be thought. Based on Avicenna’s ontology, ‘the eternity of the world’ is cosmologically affirmed, by way of thinking about the universe as ‘a necessary existent due to something else other than itself’ (wājib  d bi-ghayrihi); since the cosmos is contingent-in-its-self, al-wuju necessary-through-an-other (El-Bizri, 2001, pp. 753–778). The implied intersection of ontology with cosmology and natural philosophy is not explicitly explored or directly interrogated by Glasner, even though she tangentially approaches this theme through Averroës’ critique of ‘Neo-Platonist contaminations’ of Aristotelianism (Glasner, 2009, pp. 85–91). Aristotle, Alexander of Aphrodisias, al-Ghazālı̄ (and possibly alNazzām), all are gathered together in Averroës’ deconstruction of determinism (of Physics VIII) and the distinction he established between two interconnected physical systems that were correlative with the bifurcated cosmology of the ‘Supra-Lunar’ and the ‘SubLunar’ spheres (‘the heavens and divinities, the earth and mortals’). The necessity of the perpetual and continuous heavenly motion grounds the dependent contingency of the temporal and contiguous earthly motion. Determinism and necessity are celestial, while indeterminism and contingency (qua possibility) are terrestrial. Perhaps this describes a ‘vertical’ natural order instead of a horizontal non-hierarchical one (Glasner, 2009, pp. 79–83). The apparent perpetuity in the Sub-Lunar locomotion is not essential, but is rather derived from the eternity of the motion of the outermost celestial sphere. Eternity and perpetuity are essential in the heavenly continuous motion and accidental in the earthly contigu th al-dā’im) ous locomotion. ‘Perennial regeneration’ (al-hudu would be more adequate than ‘eternity’ (qidam) per se in thinking about Sub-Lunar motion. As a thinker in his own right, Averroës does not simply endorse the position of the falāsifa, nor does he  n (Glasner, 2009, readily reject the doctrines of the mutakallimu pp. 107–108). Averroës deconstructed the Aristotelian conception of motion as being a ‘continuous homogeneous phenomenon’ following the propositions of books III, V and VI of the Physics. Averroës did not explicitly reveal his deviation from Aristotle’s views; he rather advanced interpretations of the Aristotelian theses that opened them up to novel philosophical horizons and new directions in thinking, which were properly his own. This applies to his theory 214 N. El-Bizri / Studies in History and Philosophy of Science 42 (2011) 210–214  rat al-haraka), which is conof forma fluens (‘form of motion’; su trasted with the fluxus formae thesis (‘flow of form’; sayalān al ra); with St. Albertus Magnus (d. 1280 CE) attributing the former su to Averroës and the latter to Avicenna (Glasner, 2009, pp. 112–114; McGinnis, 2006, 190–191). Averroës’ forma fluens theory reflects on ontological perspective on ‘the kind of being of motion’. If we state that motion is essentially identical with the end it reaches, then we advocate a forma fluens thesis, whereby motion (haraka; kinēsis) is seen as perfection (kamāl; entelekheia). Motion is thus grasped as being of the same genus with the ‘perfection’ towards which it proceeds; namely, its telos (ghāya). However, if we conceive motion as a gradual constitutive cum generative process, then we take it to be a homogeneous fluxus formae (Glasner, 2001, pp. 9–26; Glasner, 2009, pp. 109–112). If we turn to Physics VI.4, it is stated that ‘everything that changes must be divisible’. This proposi tion is interpreted by Averroës as an affirmation of the view that ‘motion was not a continuum’. Consequently, all change is temporal and heterogeneous, rather than being instantaneous or homogeneous. Motion is thus a forma fluens instead of being a fluxus formae. The ‘continuous interval’, which is in-between the start and the end rest points, as a lapse between the terminus a quo and the terminus ad quem, is replaced by the notion of a ‘contiguous chain’. Essential change happens between two states of rest within the interval that separates them. The nature of motion in the Sub-Lunar realm is that of a dynamic ‘contiguous chain of intermediate changes that are not separated or interrupted by states of rest’ (Glasner, 2009, pp. 123–126). Let I be an interval between the starting point To (terminus a quo), of a given motion M, and its ending point Tem (terminus ad quem), such as: To?Tem, then, I is not a ‘homogeneous continuum’ but rather ‘a chain of heterogeneous contiguity without rest’, such as: To?i0 ?i00 ?i000 ?Tem. As Glasner argues, Averroës endeavoured also to deconstruct the Aristotelian idea of ‘homoeomerity’; namely, that the parts of a given physical body are similar to one another and to the whole (Glasner, 2009, pp. 141–171). This notion is supported by the presupposition of isomorphism between the mathematical and the physical properties of magnitudes, of time and motion, and is furthermore reinforced by the thesis of minima naturalia (minimal parts), which denies the infinite divisibility of a physical body, and may have been influenced by atomism. As Glasner explains, Galen conceived unity in terms of ‘homoeomerity’, with a stress on Stoic ‘continuity’, while Alexander grasped it by way of an adaptive interpretation of Aristotelian ‘essentialism’ (Glasner, 2009, p. 151); what I would refer to in this context as ‘Aristotelian ousiology’, namely, as an ousia-(substantia)-ontology (El-Bizri, 2001). Averroës distinguishes between the ‘parts’ of a physical body, and ‘wholes of parts’, with the latter class pointing to ‘First-moved’ types (mutaharrik awwal; primum motum), and is at the core of the minima naturalia thesis (Glasner, 2009, pp. 151–153). The ‘Firstmoved’ is essentially movable as a minimal part and indivisible magnitude; since its divisibility is not impossible per se (otherwise this would be squarely an orthodox claim of atomism), rather its indivisibility is related to what it is in its quiddity, given that any further division would render it something other than itself. Hence, the essentially ‘First-moved’ is a minimal part that cannot be divisible, given that its divisibility will turn it into something else other than what it is. Averroës dismantles ‘homoeomerity’ and denies continuity in the physical body. He also holds that matter is the agency for being moved and for being a divisible entity, while form is the faculty for moving and being indivisible. The minimal part exists in actuality by way of generation and not division. The minima are the building blocks of the physical body. Hence, no physical magnitude is infinitely divisible; albeit, the minima are not the same as ‘atoms’ per se, given that they are essential-substantial composites of matter and form, endowed with natural motion. Consequently, the continua, which are infinitely divisible, belong to the domain of geometry and not physics; while the physical body is composed of minima. The continua are abstract mental notions (dhihnı̄); namely, continuities of time, distance, and motion that exist only in the intellect (al-‘aql). They are mathematical rather than being corporeal and physical. This thesis is ultimately described by Glasner as: ‘Aristotelian atomism’, which ‘tames’ the atomist physics of Kalām through the agency of interpreting Aristotle’s natural philosophy in novel ways (Glasner, 2009, pp. 155–159) that reflect Averroës’ cultivation of the idea of harmony and dialogue between ‘reason and faith’, ‘science and religion’ (Averroës [Ibn Rushd], 1976). The persona of Averroës is confirmed again not only as being that of a towering figure in history of philosophy, but also as that of a highly influential polymath in history of science! Despite what is potentially appraisable as lacunae in elucidating selected fundamental questions, which persisted as desiderata, Glasner’s Averroes’ Physics contributes considerably to our understanding of the scientific and philosophical legacy of Averroism. This book can be deservedly classed amongst the prominent contributions in this field of study; to be situated elegantly alongside the works of eminent scholars like G. Anawati, S. van den Bergh, M. Bouyges, G. Endress, G. F. Hourani, J. Puig Montada, E. I. J. Rosenthal, and S. Zayid. References Aristotle (1936). In D. Ross (Ed.), Physics. Oxford: Oxford University Press. Averroës [Ibn Rushd] (1950). In S. Dunya (Ed.). Tahāfut al-tahāfut (Vol. 2). Cairo: Dār al-ma’ārif. Averroës [Ibn Rushd] (1954). The incoherence of the incoherence (S. van den Bergh, Trans.) (Vol. 2). Oxford: Oxford University Press. Averroës [Ibn Rushd] (1976). On the harmony of religion and philosophy (G. F. Hourani, Trans.). London: Luzac & Co.  z (Eds.). 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