Unpublished, Nov 2004
The problem of essence and existence cuts to the heart of metaphysics, or the study of being qua being, and by way of Muslim philosophy, took on profound significance in the wake of its transmission to Mediaeval Europe. Although a feat of Greek philosophy, the Muslims, like St. Augustine in his time, elevated it to a different level by incorporating it into a theological dimension. The present disquisition, however, does not claim to survey the entire sweep of thought prevalent among Muslim philosophers (hereafter falāsifa, sg. faylasūf) so much as it attempts to explore the central polemics therein. To this end, it is divided into two parts. Given his immense influence, the first part will focus on Ibn Sīnā’s distinction between essence and existence and his particular conception of being. The second part then proceeds to explore the philosophical debate that developed afterwards, engaging such key voices as Ibn Rushd, al-Ghazālī and to a lesser extent, the Illuminationists.
The Ontological Problématique
Among early falāsifa, Abū ‘Alī al-Ḥusain Ibn Sīnā (Avicenna, 980-1037) is commonly attributed with the first, fully developed distinction between essence and existence. Whether he intended a real, ontological distinction from the mental, logical one remains debatable; nevertheless, it permeated his entire philosophy. Like al-Fārābī and most of the Peripatetics up till the time of Ibn Rushd, Ibn Sīnā unwittingly tended toward a Neoplatonised Aristotelianism, so amply illustrated in the influence of the apocryphal Theology of Aristotle (Plotinus’ Enneads in reality). For Ibn Sīnā, essence precedes existence, everything else apart from the Necessary Existent being contingent upon Him for its existence – wherewith the separation of created from Creator. Accordingly, existence is added to the essence of all beings which, apart from the Necessary Existent, do not possess existence as an intrinsic part of their essence. This idea is not new, having been inherited from his predecessor Abū Nasr al-Fārābī (Abunaser, ca. 870-950):
We admit that essence and existence are distinct in existing things. The essence [māhiyya] is not the existence [hūwiyya] . . . . If the essence of man implied his existence, to conceive his essence would also be to conceive his existence . . . . By the same token, existence is not included in the essence of things; otherwise it would become one of their constitutive characters, and the representation of what essence is would remain incomplete without the representation of its existence. And what is more, it would be impossible for us to separate them by the imagination. But that is not the way it is . . . . [t]hus existence is not a constitutive character, it is only an accessory accident.
The essence or quiddity of a thing as such is distinct from its existence. But what constitutes essence? In this regard, Ibn Sīnā’s metaphysics is largely Aristotelian. Essence may be said to be the intrinsic property per se of a thing that defines it as such and that without which the same would not be identified as such. In other words, it responds to the question ‘what is it?’ (Lat. Quid est?). John is in essence a being with both a soul and a material body. But he could also be properly called a man or an animal in the wider sense. Ibn Sīnā thus distinguishes between genus (animal, general), species (man, specific) and individual (John), all of which could be predicated of John to varying degrees of exactitude/inclusivity, though not vice versa: John is a man and even an animal, but not all men or animals are John. On the other hand, John’s ‘tallness’ and ‘smartness’ are merely accidental to him, that is, they do not constitute his essence in an absolute sense or reply to the question ‘what is John?’. They merely add to his description. Even so, Ibn Sīnā asserts, “it is insufficient to demonstrate what is essential by saying ‘that which is inseparable’, for many non-essential things are not separable”. This point, however, will be taken up shortly under ‘concomitant accidents’.
Essence falls into three categories: as concrete existent, as conceived idea and as essence per se. While the first two are explicit, the third requires closer examination. Essence per se is essence considered in itself, devoid of any relation to existing things or mental concepts, and is thus free of universality or particularity, potentiality or actuality, unity or multiplicity, for instance. For this reason, a horse can be the universal idea of ‘horse-ness’ or ‘equinity’ in one’s mind and a particular steed in reality at once without creating a contradiction. Essence is also one, simple and indivisible, such as ‘whiteness’ to white and ‘triangularity’ to triangles; however, since the notion of unity is not constitutive of a thing’s essence per se – ‘equinity’ being neither one nor many – it is a concomitant and therefore an accident. If ‘one-ness’ does not command a generic or specific definition (definition being that which expresses a thing’s essence), neither does being or existence for Ibn Sīnā. Human-ness can be predicated of all men because it is in their intrinsic nature to be human, yet not all men are existent at once or even existent at all. In point of fact, “quiddity [essence] is a thing, be it a man, a horse, an intellect or a soul. Only after that is it qualified by one and existent”.
Before proceeding, it may be useful to highlight certain nuances that Ibn Sīnā delineates for essence (Gk. to ti ēn einai), three of which concern us. Māhiyya is quiddity (lit. ‘what-ness’) considered in itself, that of secondary substances. It is thus the essence common to all beings of the same species or genus. Hūwiyya refers to the ipseity (lit. ‘self-ness’) of primary substances, that is, of all individuated, realised beings. ‘Anniyya, haecceity (lit. ‘this-ness’), refers to the individual existent (le ‘je’ existant of Goichon) but in an abstract and removed sense, and is also used to refer to the divine essence. In a broader context, both hūwiyya and ‘anniyya also denote existence (wujūd), if existence is to be defined as the actuation and individuation of a thing’s essence.
The basis of being, whether in essence or existence, is substance (jawhar). The first of Aristotle’s Ten Categories and the only one self-subsistent, substance denotes a thing which is not itself contained in a subject or receptacle (whether or not in matter), and is therefore the bottom-most substrate of all existents. If a thing is in a subject, it cannot be said to be a substance, and thus the argument regresses ad infinitum until its substance is ascertained. This is properly called primary substance, reducible to the individual (John). Secondary substances, that is species (man) and genus (animal), are predicable of primary substances (not in them) but not vice versa. John is a man, then an animal, but not all men or animals are John. Broadly speaking, substances consist of four modes: absolute matter, a substrate in itself but only possible in concept; absolute form, such as Intellect (‘aql) which is not joined to matter; form in matter, “as the soul [nafs] is in the body”; and finally, the fusion of form and matter, the basis of sensible existents or bodies (jism). In physical reality however, form and matter are inseparable, and although form is somewhat prior to matter, it is not in the sense of being its cause. While matter merely receives substance-ness in its potentiality (that is, prior to its coming-to-being), form actuates substance as such, without which one may not speak of any substance at all. Form is the determining principle of matter, though in a way, matter also individuates form by allowing it to assume concreteness, and from this, numerical and individual difference.
On the other hand, accidents only subsist in a subject or receptacle, are predicable of both primary and secondary substance, and constitute a third category after (the conjunction of) form and matter. Accidents correspond to the remaining nine categories after substance: quality, quantity, relation, time, place, position, state, action and affection. Thus, John (substance) could be white (quality), one/alone (quantity), sitting (position) in a park (place) at noon (time), bored (state) though not as bored as the person on the next bench (relation), watching people (action) and being watched (affection), yet all of these could easily not be predicated of him. Two types of accidents follow: concomitant/essential (lāzim or lāhiq) and non-concomitant/non-essential (‘arad). Concomitants do not constitute a thing’s essence in the strictest sense, yet necessarily accompany it. A triangle is essentially three sides, and though the sum of all three equals to two right angles, the latter is posterior to the former, even as it is inseparable from the triangle. Similarly, to laugh is to be human, but though the two are inseparable, laughter does not in essence define humanity. Non-concomitants neither constitute a thing’s essence nor accompany it by necessity, such as the size or colour of a triangle. Now, concomitants either originate from within, like the two right angles of a triangle, or from without. To the latter category, Ibn Sīnā designates existence. Accordingly, rather than being non-concomitant, existence is an accident in the concomitant sense.
Matter and form are closely linked to potentiality and actuality: while matter allows for the possibility of being, form perfects its coming-to-being. Given his emanatist orientation, Ibn Sīnā’s essence (pure possibility), once intellected by the Active Intellect (al-‘aql al-fa‘āl, also ‘Giver of forms’, wāhib as-suwar), simply awaits its conjoining with existence in order to be self-actuated. Nowhere is essence equated to non-being, only that it possesses non-being insofar as it has yet to receive existence. Goichon further points out that “existence does not follow [from essence] immediately, but mediately [that is, through an intermediary], by way of a necessary, external act. The point of Ibn Sīnā’s distinction is clearly to establish the transcendence and omnipotence of the First Being and the dependence upon His existential abundance of all other beings on the one hand, and in a way, to obviate pantheism by imbuing essence with a certain ontological independence on the other. As she continues, “necessary existence is to the First as quiddity is to other beings,” that is, His existence is His essence and vice versa. Indeed, since all essence ‘awaits’ existence, one may describe Him as devoid of essence. As such, He transcends all genera, species, differentiae and effectively, definition. Since He cannot be captured as an “object of discursive thought” apart from pure existence (‘anniyya), the Necessary Being should also be “characterized negatively”, devoid of all qualities that may render Him comparable to created beings. Because He is immaterial, He is pure actuality as well as pure good, evil being a function of matter, and since He is One and indivisible, He is the Intellect, the Intellecting and the Intelligible all at once (Gk. nōesis noēseos).
Following the distinction between essence and existence, Ibn Sīnā proceeds to describe three types of existence, necessary, possible and impossible, a schema original to him. Necessary (wājib) existence is that whose non-existence is impossible and absurd. Because all beings ultimately require their existence from one whose existence is not derived and merely possible (otherwise, an infinite regress would ensue, and it is impossible that there should exist an infinite number of possible causes and beings), it follows that this being is necessarily existent. The Necessary Being is thus God, whose existence and essence are identical, and is singular unto Himself. Necessary existence is further divided into two categories: necessary in itself (in se), and necessary by another (per aliud). As the preceding example illustrates, God is necessary in se. That which is necessary by another, however, is that whose existence in itself is merely possible, but made necessary by another. In a sense then, one may also call this possible being, whose necessity derives from another. Thus, 4 is necessary not in itself, but only by the factor of 2. Possible (mumkin) existence is that whose existence or non-existence could be equally conceived of, and that neither would constitute a contradiction in any terms. The world of generation and corruption and everything whose existence is not part of its essence represent possible existence. Possible in this case does not refer to being in potentiality as opposed to being in actuality, but rather the simple possibility of being at all. Impossible (mumtani’) existence, even though logically conceivable such as a unicorn, does not correspond at all to anything in reality and is therefore categorically not possible.
The brilliance of his ontology notwithstanding, Ibn Sīnā occasionally succumbs to ambiguity. A problem arises for instance when he identifies ‘possible in se’ with, after its actuation, ‘necessary by another’. In other words, in its coming-to-being, the possible becomes necessary. Goichon notes that while the faylasūf distinguished possible existence from being in potentiality earlier, it is precisely to this proposition that he returns when he asserts “the necessity of the actuated possible being”. Only in light of Neoplatonism would this seeming contradiction make sense, since by it, emanation renders the entire order of existence necessary. A second problem concerns the apparent conflation of quiddity in se and quiddity as a mental concept. Refuting Plato’s theory of independently existing forms, Ibn Sīnā asserts such a possibility as existent only in the mind whereas only shortly before he declared its total privation of all relation to existing things or mental concepts. In this connection, Marmura observes, he is also vague when describing the type of quiddity – whether in se or concrete – inherent in the celestial intelligences “prior to multiplicity”; again, he seems to conflate them. Be that as it may, Ibn Sīnā does attempt to illustrate his essence-existence distinction in more lucid terms, namely, that of a distinction between two types of existence: ‘affirmative existence’ (al-wujūd al-ithbātī) affirms that a thing is, that it exists in reality; ‘proper existence’ (al-wujūd al-khāss), on the other hand, posits what a thing is, namely its essence. If “the essence of a thing, regarded in itself and without its cause, would not exist,” then, as Oliver Leaman muses, what is wrong with stating that “existence cannot be [therefore] included within the essence of a thing”? Though Ibn Sīnā may have merely intended a logical separation between a thing’s essence and its existence or what exists in the mind and what exists in actuality, his conception gave rise to much heated debate as discussed in the next section.
The Philosophical Réplique
In response to the Avicennian essence-existence distinction, Abū’l-Walīd Muhammad Ibn Rushd (Averroes, 1126-98) argues that his predecessor’s faux pas was in postulating existence as accidental to essence. Ibn Sīnā held that to know “if something exists, it is firstly necessary to know what it is, to know its definition, to know its essence . . . and hence, essence precedes existence, both logically and ontologically”; Ibn Rushd contends that definition as such is merely nominal, that is, it only defines the meaning of the word designating the thing and not the thing itself. Without a thing first existing, its essence can never be objectively apprehended and abstracted from. As such, if existence does not precede essence, both are at least coterminous. Alternatively, if being precedes privation, he reasons, and possession also precedes privation, then essence without existence (i.e. privation) could not possibly precede being, neither in substance, nor in accident. At the root of this problem, Ibn Rushd charges Ibn Sīnā with conflating ‘being’ with ‘one’ (the famous ens et unum convertuntur of Latin Scholastics) in both the latter’s senses as numerical principle and simplicity/indivisibility (as in ‘God is One’). Given that ‘one’ in its numerical sense is an accident, it is not surprising that ‘being’ by association becomes an accident. In the Andalusian philosopher’s words:
Avicenna made a big mistake here. He thought that unum [one] and ens [being] signified dispositiones added to the essence of a thing . . . . If unum and ens have the same meaning, then, he thought, it would be meaningless to say, ens est unum. It would be the same as saying, unum est unum, and ens est ens. This, of course, does not follow . . . . These terms express the same basic content, but they do so in different manners. They do not add . . . to the essence itself.
A parallel source of confusion, according to Léon Gauthier, Etienne Gilson and Oliver Leaman may be spelled out as such. Between ‘being’ (mawjūd) and ‘existence’ (wujūd) – the first merely possessing a copulative function within a categorical proposition (e.g. John is white, in other words, it is true that John is white) and the second denoting the opposite of non-being, Ibn Sīnā appears to have had the former in mind when describing existence as accidental to essence. ‘Being’ as a copula is applicable to all ten categories (substance and the nine accidents); ‘Existence’, however, is only predicable of substance, and since, as was already established, the other nine categories can only exist in substance (in a subject or receptacle), by extending ‘existence’ to all ten categories, Ibn Sīnā blurs the distinction between logical-analytical ‘being’ and real ‘existence’. The confusion between real existence and ‘to be’ as a verb and syntactic element (copula), explains why Ibn Sīnā likewise subordinates existence (as verb) to essence (as subject). To illustrate, without the ‘is’ in the proposition ‘essence is pure’, ‘essence’ may lose both the quality ‘pure’ and its ‘is-ness’ or being, yet it remains self-subsistent.
Again, Ibn Rushd argues that existence should be understood in the sense antithetical to non-being. Rather than a mere copula, existence is the very subject, the substance and the essence itself. Such views were echoed in later, particularly Christian thinkers such as Thomas Aquinas, for whom essence cannot exist without existence since the latter is the very act or coming-to-being of the former. Ironically, in his scathing Tahāfut al-Falāsifa (The Incoherence of the Philosophers), Abū Hāmid al-Ghazālī (Algazel, 1058-1111) adopts Ibn Sīnā’s proposition that essence could be conceived of without itself being existent, only to turn it against the assertions of the Peripatetics. Refuting their eternity of the world thesis for example, he argues that “if we can accept that the idea of something coming from nothing is a possible thought-experiment, then there is no obstacle to God’s making it actual”. In direct correlation, al-Ghazālī extends this polemic to Ibn Sīnā’s concept of possible existence. If universality was a mere mental construct as Ibn Sīnā alleged, so too would the notions of necessity, possibility and impossibility by the same logic. That impossibility corresponds to nothing in reality is symptomatic. In the event, the relation between necessary and possible proven to exist only in the mind, this particular argument could no longer effectively be used to demonstrate God’s existence. As a corollary, the necessary eternity of matter as substrate also becomes untenable. In only partial defense of the falāsifa, Ibn Rushd counters al-Ghazālī in the former’s Tahāfut at-Tahāfut (The Incoherence of [al-Ghazālī’s] Incoherence) by demonstrating that the very conception of universals implies possibility: to the degree that universals possess both independence in the mind and potentiality in the external world, so too they are possible in themselves. Possibility as a notion is therefore also a signifier for potentially occurring things. In line with Aristotle’s ‘principle of plenitude’, what is possible will necessarily be at some point in time if it is not already at present, otherwise, like a unicorn, though conceivable in the mind, it is impossible. Indeed, this rebuttal was also directed at Ibn Sīnā’s view that what is possible may not be brought into existence. Invoking the eternal nature of the world, Ibn Rushd maintains that everything that is possible will become actual, and that it is absurd to suppose otherwise. Rejecting both Ibn Sīnā and al-Ghazālī’s justification that possible existence requires an external actuator, he rejoins by holding that a thing becomes by its very essence alone. Granted, the universe depends on the Necessary Being, but that does not mean that He could not have created it complete with all its causal relations in place right from the beginning. If an effect can be dissociated from its cause (in the case of fire and cotton producing sugar instead of ash), then its definition (ash) can never be objective; and were such minutiae to be constantly subject to divine caprice (miracles being altogether different and beyond this essay’s scope), then the very basis of reason is in question.
Furthermore, Ibn Rushd attacks the proposition that something could be both possible in se and necessary by another. Unless one is willing to admit a change in a thing’s essence, which is clearly impossible in Ibn Sīnā’s universe, it is absurd to suppose this state of affairs even possible – that is, unless it refers not to being but to motion, in which case the assertion would make perfect sense. Unlike being, motion must derive its impetus from an external mover; and if motion is eternal – a hallmark of Aristotelian metaphysics – it follows that this external mover is unmoved. While most of Avicennian philosophy endeavours to adhere to that of Aristotle (his Plotinian influences arriving by way of pseudo-Aristotelian apocrypha), he does differ on this count in particular. Briefly, like al-Fārābī, Ibn Sīnā states that the First Principle is the First Cause of all being, the efficient cause, rather than simply Aristotle’s First Mover. In other words, the First Being does not merely set the universe into motion by way of the empyrean, but is engaged in the very act of bringing-to-being or in this case, ‘emanating’:
[I]t is inappropriate to argue to the First Truth from motion – that is, from the proposition that the first is the principle of motion. It is incumbent on those who [do] this to posit a [separate] principle of essences, for they have done no more than to show that [the first] is a mover, but not that He is a principle of being.
Another philosophical current relevant to the debate under consideration – and one possibly influenced by the mysticism of Ibn Sīnā’s ‘Oriental philosophy’ – is the Illuminationist (ishrāqī) school founded by Shihāb ad-Dīn Yahia as-Suhrawardī (1154-91) in Persia. That it is characterised by two opposing trends – the primacy of essence (asālat al-māhiyya) v. the primacy of existence (asālat al-wujūd) – warrants brief mention before concluding. Suhrawardī distinguishes between existence universal to all concepts and existence particular to existents, arguing that since existence as a concept necessarily depends on the presence of existents to make sense and that since all existents require an essence to exist, essence must therefore precede existence. To say that existence precedes essence is to say that existence itself exists, and thus begins a regression ad infinitum. In a manner reminiscent of Plato’s Ideals, intelligible ideas (essences) dominate the higher realms closer to the Light of Lights (nūr al-anwār, Suhrawardī’s First Being) whereas material, sensible existents or ‘isthmuses’ (barzakh) inhabit the lower realms and this world. However, despite its inferiority, positing existence as a property of essence – as Ibn Sīnā does – would create the problem of trying to ascertain the nature of essence prior to the addition of existence. Furthermore, while Suhrawardī avers that all beings are contingent on the First Light (existence being contingent on essence), he also argues that since the existence of a thing renders its contingency necessary and since the non-existence of another renders its non-existence not-possible, it follows that a thing can only either be necessary or impossible. At the other end of the ontological spectrum, Sadr ad-Dīn ash-Shīrāzī (Mullā Sadrā, 1572-1640) asserts the Reality of Being (haqīqat al-wujūd, cf. the Sūfis’ wahdat al-wujūd ), to which essence or form provides but the individuating circumstances. Put another way, a thing has to first exist – this existence being one and universal to all existents – in order for its description or definition (i.e. essence) to be grasped. While all beings mirror the First Light (albeit in gradations) insomuch as their existence emanates from Him, it is their individual essences that engender ‘darkness’, as it were. For Mullā Sadrā, God is all Being and no essence. Hence, the lower the ontological plane, the greater the multiplicity of essences and the lesser the reality. For him then, essence is contingent and existence, necessary.
As was mentioned at the beginning, though Ibn Sīnā may not have intended an actual, ontological distinction between essence and existence, the acute reaction to his thesis surely bears testament to the polemic’s place within Muslim philosophy. What this essay has sought to achieve vis-à-vis the essence-existence problématique is to juxtapose the Neoplatonised Peripateticism embodied in Ibn Sīnā against two other specific traditions – the ‘neo-Aristotelianism’ which Ibn Rushd hoped to attain by purging Peripateticism of its Neoplatonic taints as it were, as well as the post-Avicennian Illuminationist school represented, for our purposes, by Suhrawardī and Mullā Sadrā. Though decidedly anti-philosophical in design, al-Ghazālī’s position (among that of the mutakallimūn or theologians) also helps shed some light on the limitations of the falāsifa. While nowhere near exhaustive, it is hoped that the foregoing exposition has at least sketched an aspect of the vast intellectual contribution of Muslim thinkers vis-à-vis the ongoing development of philosophy, both in the East as well as the West.
 See Amélie-Marie Goichon. La Distinction de l’Essence et de l’Existence d’après Ibn Sīnā (Avicenne). Paris: Desclée de Brouwer, 1937, 133: “Donc tout être dont l’ipséité n’est pas la quiddité, ni un des constitutifs de celle-ci, tient d’autrui son ipséité. Cela aboutit au Principe qui n’a pas de quiddité se séparant de l’ipséité.”
 Cited in Francis A. Cunningham. Essence and Existence in Thomism: A Mental vs. the “Real Distinction”?. Lanham: University Press of America, 1988, 130-1.
 See in particular Book VII, Aristotle. Metaphysics, Books I-IX. Trans. Hugh Tredennick. UK: William Heinemann Ltd, 1975.
 See also Goichon, La Distinction, 461.
 Cited in ibid., 57: «Il ne suffit pas, pour faire connaître l’essentiel, de dire qu’il signifie: «ce qui est inséparable», car beaucoup de choses non essentielles ne se séparent pas . . . »
 Etienne Gilson. L’Etre et l’Essence. 2nd ed. Paris: Librairie Philosophique J. Vrin, 1981, 124; cited in Michael Marmura. Quiddity and Universality in Avicenna’. In Neoplatonism and Islamic Thought. Parviz Morewedge, ed. New York: State University of New York Press, 1992, 84.
 Gilson, L’Etre et l’Essence, 124.
 Cited in Goichon, La Distinction, 141: «La quiddité est une chose, soit un homme, soit un cheval, ou une intelligence, ou une âme. Ensuite cela sera qualifié d’un et d’existant.»
 Ibid., 48.
 “Indeed, the question which was raised long ago, is still and always will be, and which always baffles us – “What is Being?” – is in other worlds “What is substance?”, Aristotle, Metaphysics, VII.i.
 Goichon, La Distinction, 19: «On appelle substance . . . toute essence dont l’être n’est pas dans un sujet d’inhésion.»
 Seyyed Hossein Nasr & Oliver Leaman, eds. History of Islamic Philosophy Part I. London: Routledge, 1996, 240; Ibn Sīnā. Le Livre de Science I: Logique, Métaphysique (Dânesh-nâmè). Trans. Mohammad Achena & Henri Massé. Paris: Société d’Edition «Les Belles Lettres», 1955, 95.
 Ibn Sīnā. Livre des Directives et Remarques (Kitāb al-‘Išārāt wa’l-Tanbīhāt). Trans. A.-M. Goichon. Paris: Librairie Philosophique J. Vrin, 1951, 270-2; G. Verbeke. Introduction. Avicenna Latinus: Liber de Philosophia Prima sive Scientia Divina I-IV. By Ibn Sīnā. Trans. Simone Van Riet. Leiden: E. J. Brill, 1977, 93.
 Goichon, La Distinction, 22.
 G. Verbeke, Avicenna Latinus, 92.
 Goichon, La Distinction, 424, 467-8: “[Q]uand il y a multiplicité de formes quidditativement semblables «elles diffèrent seulement selon ce qui reçoit la quiddité, ce à quoi la quiddité a un rapport propre, et cela, c’est le corps». Tandis que si l’âme pouvait exister sans le corps, il n’y aurait pas de différence numérique entre les âmes.”
 Ibid., 23.
 Ibid., 114-5.
 Nasr & Leaman, History of Islamic Philosophy Part I, 240.
 Goichon, La Distinction, 118; cf. the Latin “id quod accidit quidditati”, see Gilson, L’Etre et l’Essence, 129.
 Goichon, La Distinction, 141; See also Leo J. Elders. The Metaphysics of Being of St. Thomas Aquinas in a Historical Perspective. Trans. John Dudley. Leiden: E. J. Brill, 1993, 209.
 Goichon, La Distinction, 143: “Elle [existence] n’en découle pas immédiatement, mais médiatement, par une action extrinsèque nécessaire.”
 Léon Gauthier. Ibn Rochd (Averroès). Paris: Presses Universitaires de France, 1948, 159-60.
 Goichon, La Distinction, 344: “L’existence nécessaire appartient au Premier comme la quiddité appartient aux autres êtres.”
 Gilson, L’Etre et l’Essence, 128: “Primus igitur non habet quidditatem.”
 Ibn Sīnā, Al-‘Išārāt, 370; Goichon, La Distinction, 152.
 Majid Fakhry. A History of Islamic Philosophy. No. 5, Studies in Oriental Culture. New York: Columbia University Press, 1970, 174-5.
 See Ibn Sīnā, Dânesh-nâmè, 150.
 Cited in Goichon, La Distinction, 160.
 Cited in ibid., 162: «tout possible en soi, si son existence est mise en acte, ‘in hasala wujūduhu, est nécessaire par autrui».
 Ibid., 164: “Au début de cet exposé, il a expressément écarté, comme sens du «possible» dont il parle, «ce qui est dans la puissance»; donc «possible» par opposition à «actuel», à l’être en acte. Et voici qu’à la fin c’est précisément sous cet angle qu’il se place pour établir la nécessité du possible réalisé.”
 Ibid. loc. cit.: “On peut proposer cette interprétation de sa pensée: le possible en soi reste possible en soi; l’acte qui le fait exister est extrinsèquement nécessaire. Le possible réalisé reste possible par nature mais il est dans l’état de réalisation nécessaire. Cette nécessité ne peut en vérité être établie que par le système de l’émanation rendant nécessaire tout l’ordre du monde. Mais, déjà persuadé de cette nécessité, Ibn Sīnā a essayé de l’établir logiquement, à partir de l’idée de possible existent, et il n’y a pas réussi.”
 Marmura, ‘Quiddity and Universality in Avicenna’, 83.
 Ibid., 83-4.
 Robert Wisnovsky. ‘Notes on Avicenna’s Concept of Thingness (Šay’iyya)’. Arabic Sciences and Philosophy vol. 10 (2000): 193.
 Ibid. loc. cit.; Oliver Leaman. Averroes and His Philosophy. UK: Oxford University Press, 1988, 108-9.
 Ibid., 104.
 Gauthier, Ibn Rochd (Averroès), 153-4: “Ibn Sīnā constate que pour se demander «si une chose existe» il faut d’abord savoir de quelle chose il s’agit, donc en avoir une definition, en connaître l’essence . . . . Ibn Sīnā conclut de là que l’essence est antérieure à l’existence, logiquement et ontologiquement, que l’existence ne fait point partie de l’essence, qu’elle est un accident surajouté à l’essence.”
 Ibid., 154.
 Leaman, Averroes and His Philosophy, 105.
 Gauthier, Ibn Rochd (Averroès), 154.
 Ibid. loc. cit.; See also Cunningham, Essence and Existence in Thomism, 136-7; this is, however, not a view adopted by Goichon. See La Distinction, 10-11: “Ibn Sīnā a-t-il vraiment confondu l’unité transcendantale et l’unité numérique? Certainement non. Ici même, on vient de lire combien il met les mathématiques à part de la métaphysique, tout en reconnaissant que l’un est . . . objet de la métaphysique . . .”
 Cited in Cunningham, Essence and Existence in Thomism, 136-7.
 Gauthier, Ibn Rochd (Averroès), 155-6; In addition, Gauthier charges that in so doing, Ibn Sīnā unwittingly contradicted the entire basis of being underlying Peripatetic philosophy, both classical and Islamic; Gilson, L’Etre et l’Essence, 69; Leaman, Averroes and His Philosophy, 104-6.
 Cf. Van den Bergh’s comment, cited in Leaman, Averroes and His Philosophy, 106.
 Ibid., 109.
 Ibid., 110.
 M. Saeed Sheikh. ‘Al-Ghazālī: Metaphysics’. In A History of Muslim Philosophy. Vol. 1. M. M. Sharif, ed. Wiesbaden: Otto Harrassowitz, 1963, 601.
 Edward Booth. Aristotelian Aporetic Ontology in Islamic and Christian Thinkers. UK: Cambridge University Press, 1983, 129-30.
 Leaman, Averroes and His Philosophy, 111; Aristotle, Metaphysics, IX.iv.
 Ernest Renan. Averroès et l’Averroïsme: Essai Historique. 3rd ed. Paris: Michel Lévy Frères Libraires Editeurs, 1866, 112: “La série des générations est infinie a parte ante et a parte post: tout ce qui est possible passera à l’acte . . . et puis, dans le milieu de l’éternité, il n’y a pas de différence entre ce qui est possible et ce qui est.”
 See also Rafael Ramón Guerrero. ‘Sobre el Concepto de Materia en Averroes. A Propósito de la «Izquierda Aristotélica» en la Filosofía Árabe’. In Al Encuentro de Averroes. Andrés Martínez Lorca, ed. Madrid: Editorial Trotta, 1993, 78-9: “Una división más adecuada del ser, más acorde con la realidad, es la que establece la división del ser en acto y ser en potencia. Es ésta la que le permite entender el universo no como un ser posible que recibe la existencia de otro, sino como un todo necesario, organizado en virtud de unas leyes, que son las causas del universo . . .”
 Oliver Leaman. A Brief Introduction to Islamic Philosophy. UK: Polity Press, 1999, 43.
 Leaman, Averroes and His Philosophy, 113: “There can of course be no change in essence, since on Avicenna’s account existence, possibility, and necessity are accidental and only externally related to a thing and its essence or nature.”
 Ibn Rushd. Grand Commentaire de la Métaphysique d’Aristote (Tafsīr Mā Ba‘d At-tabī‘at): Livre Lam-Lambda. Trans. Aubert Martin. Belgium: Société d’Edition «Les Belles Lettres», 1984, 1632: “Mais qu’il existe une chose qui soit substantiellement possible mais dont l’existence soit nécessaire par autrui, cela ne se peut, car une même chose ne saurait être à la fois possible du fait de sa substance, et recevoir d’autrui l’existence nécessaire, à moins que la nature de cette chose ne puisse être transformée.”
 Nasr & Leaman, History of Islamic Philosophy Part I, 189.
 Cited in Booth. Aristotelian Aporetic Ontology, 109.
 Mehdi Amin Razavi. Suhrawardi and the School of Illumination. Surrey, UK: Curzon Press, 1997, 33-5.
 Suhrawardī. The Philosophy of Illumination (Hikmat al-Ishrāq). Trans. John Walbridge & Hossein Ziai. Utah: Brigham Young University Press, 1999, 46; Leaman, A Brief Introduction, 91.
 Razavi, Suhrawardi and the School of Illumination, 36.
 Nasr & Leaman, History of Islamic Philosophy Part I, 646-8.
 Leaman, A Brief Introduction, 94-5.
 Fakhry, A History of Islamic Philosophy, 343.