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Jews, Christians, and Muslims together make up the Abrahamic faith communities who have sought, each in their own distinctive ways, to claim the heritage of the biblical patriarch for themselves. While each community of believers has painted its own portrait of Abraham, usually in counterpoint to the other communities’ visions of ‘God’s Friend’, as each one is pleased to call him (Isa. 41: 8; Jas. 2: 13; Q. 4: 125; see Levenson 2012), they all agree that scripturally speaking the patriarch Abraham was the first monotheist. What is more, each community explicitly identifies the one God it worships in reference to the one God of Abraham, Isaac (and/or Ishmael), and Jacob (Exod. 3: 6; Matt. 22: 32; Q. 2: 133). But the confessional profile of the ‘oneness’ of the one God that Jews, Christians, and Muslims alike confess has some remarkably different features in each community’s articulation of the reasonableness of their own confessional formulas. It is no wonder then that in the wake of the Quran’s critique of the adequacy of the Jewish and Christian professions of monotheism (at-tawḥīd), that by the ninth century ce in the Islamicate world, when scholarship in all three communities was being conducted in Arabic, the topic of God’s ‘oneness’ and its meaning came up for discussion. The learned men (al-ʿulamā’), philosophers (al-falāsifah), and religious apologists (al-mutakallimūn) of each community undertook the systematic defence in the Quran’s own Arabic language of the scriptural warrants of their own community’s distinctive creedal expressions of monotheism. And nowhere did this conversation reach the level of sophistication that it achieved in the scholarly milieu of Baghdad and environs in the time of such philosophically inclined intellectuals as Abū Yūsuf Yaʿqūb ibn Isḥāq al-Kindī (d. 870), Abū Naṣr Muḥammad al-Fārābī (870–950), Abū ZakariyyahYaḥyā ibn ʿAdī (893–974), and Saʿadia ha-Gaʾon ibn Yūsuf al-Fayyumī (882–942), to name only the most prominent of them. In their hands the theoretical discussion quickly turned to the question of what it means to affirm that anything at all can be said to be one, a topic to which the Muslim philosopher al-Fārābī devoted a separate treatise, as did his Christian student and successor as the head of the Baghdadī school of Aristotelians, Yaḥyā ibn ʿAdī.1
Following a brief recollection of the interreligious, intellectual milieu of Abbasid Baghdad and her environs in the ninth and tenth centuries ce, the present study looks first into the broad range of the conversations about God’s ‘oneness’ in Islamicate religious discourse before turning more particularly to a brief discussion of the circumstances of the treatises by al-Fārābī and Yaḥyā ibn ʿAdī just mentioned, along with reflections on the topic in the works of several Jewish writers in the milieu, such as al-Muqammiṣ, Qirqisānī, and Saʿadia. The purpose is to show how it was that these several writers, Muslim, Christian, and Jewish, focused their considerable intellectual acumen on a problem that defined one of the major differences between their respective confessional communities, namely how logically to speak of the concept of the ‘oneness’ of the one God in such a way that the different nuances in the expression of the monotheism of the Jews, Christians, and Muslims might emerge clearly in the Arabic-speaking idiom of the interreligious colloquy initiated by the challenge of the Quran.
By the early years of the ninth century, many of the intellectual leaders, the ʿulamā’ of the Jews, Christians, and Muslims, had already gravitated to Baghdad and her environs making the Abbasid city the major hub of intellectual life and interreligious colloquy within the World of Islam. Once the geʾonim of the Jewish academies of Sura and Pumbedita and the patriarchs of the Christian church of the East had relocated to the city early in the century, it was not long before Muslim thinkers there and nearby, such as Abū Yūsuf Ya‛qūb ibn Isḥāq al-Kindī and Abū Bakr Muḥammad ibn Zakariyā ar-Rāzī (85–925) were doing philosophy in Arabic in dialogue with the translated texts of Aristotle, Plato, Galen, and their classical interpreters, and the Muslim theologians (al-mutakallimūn) were exploring discursive modes of speech in which they might systematically articulate Islamic belief and practice. The latter in particular were faced with discerning and marking out the critical differences between Islamic beliefs on the one hand, and the doctrines of the older monotheists on the other hand, to whose teachings they were often reacting in criticism of their adequacy. The way forward had been prepared for these intellectual undertakings by the Graeco-Arabic translation movement, under way in largely Christian hands, with the support of the caliphal establishment, since the second half of the eighth century (Gutas 1998). By the tenth century masters such as the Christian logician Abū Bishr Mattā ibn Yūnus (d. 940), the Jewish thinker Saʿadia ha-Ga’ōn ibn Yūsuf al-Fayyūmī (882–942), and the Muslim Abū Naṣr al-Fārābī (d. 950) ‘the second master’ after Aristotle had joined the conversations, to be followed in the next generation by the Christian Yaḥyā ibn ʿAdī (893–974), al-Fārābī’s student, who in due course became the leader of the Aristotelians in Baghdad in the third quarter of the tenth century, a group that was largely made up of Yaḥyā’s circle of students and disciples, both Christian and Muslim (Kraemer 1986a; 1986b).
On the philosophical front, in addition to medicine, logic and other topics, and along with the defence of the religious claims of their own religious communities, all the Baghdad thinkers of the period, Jews, Christians, and Muslims alike, were interested in ethical, moral, and political issues, both private and public. These included concerns about how best to dispel sorrows and achieve happiness, how to instil virtues and extirpate vices, how to envision ‘the perfect man’ (al-insān al-kāmil) and lead the philosophical life, and, not least, how best society should be structured and under which legal system (sharīʽa) it should be governed. Interestingly, it is in this latter context that one often finds references to interreligious concerns and to the imperative for the cultivation of ‘humane values’ (al-insāniyyah) in the relationships between communities, almost as if for these thinkers philosophy itself and the philosophical way of life could provide the only reasonable approach to inter-communal dialogue and social harmony.2 Finally, there was also the question of right religion. The scholars of the period, Jews, Christians, and Muslims, were eager to make use of their late antique philosophical heritage to commend the veracity of their own religious traditions. The Christian translator and philosopher Ḥunayn ibn Isḥāq seems to have envisioned this inter-communal role for philosophy already in the ninth century, according to a passage in the Kitāb ādāb al-falāsifah, a text often attributed to him. The bulk of the work is a collection of sayings of Greek and Persian sages and ancient philosophers, transmitted from both ancient and seemingly contemporary, gnomological sources (Gutas 1975; Zakeri 2004). But the opening narrative is an interesting, if idiosyncratic, discursive sketch of the history of philosophy, in which Ḥunayn assimilates even religious thinking and ritual behaviour into the realm of the philosophical way of life, portraying synagogues, churches, and mosques as virtual schools of philosophy (see the fuller discussion in Griffith 2008b).
The earliest Arabic-speaking Muslim philosophers were concerned, like their Jewish and Christian counterparts, to explore the philosophical dimensions of at-tawḥīd, confessing that God is one. It is significant in this connection that the discussion of ‘oneness’ (al-waḥdāniyyah or al-waḥdah) and its philosophical implications, in the light of Greek logic and metaphysics, was high on the list of the concerns of the first two Muslim philosophers whose names are still widely known, Abū Yūsuf Yaʽqūb ibn Isḥāq al-Kindī and Abū Naṣr al-Fārābī. Al-Kindī, for whom, in the words of Gerhard Endress, the cultivation of ‘philosophy was to vindicate the pursuit of rational activity as an activity in the service of Islam’ (Endress 1997: 50), spoke at some length in his treatise On First Philosophy about divine existence and ‘oneness’ (Marmura 2005: 337–53; Adamson 2003). And he also wrote a treatise specifically dedicated to laying out his logical objections to the Christian doctrine of the Trinity, precisely in terms of what he took to be its incompatibility with confessing the ‘oneness’ of God. His text now survives only in the quotations from it included by Yaḥyā ibn ʿAdī in his refutation of al-Kindī’s objections (Périer 1920–1: 3–21).3
The philosopher al-Fārābī, Yaḥyā ibn ʿAdī’s Muslim teacher, was also much interested in the philosophical implications of ‘one’ and ‘oneness’, as we mentioned above, and in fact it was in drawing on his deep knowledge of the Alexandrian philosophical and logical tradition that al-Fārābī wrote the book entitled Kitāb al-wāḥid wa l-waḥdah, a book on ‘the one and one-ness’ (Mahdi 1989). In it he discusses in some detail what one means when one says that something is ‘one’, very much, it would seem, with the Muslim doctrine of at-tawḥīd in mind. Then, in due course, with al-Fārābī’s ideas very much in the background of his own thinking, Yaḥyā ibn ʿAdī wrote his own aforementioned, philosophically and logically attuned monograph, Maqālah fī t-tawḥīd,4 in order systematically and positively to set out his reasoning in defence of the Christian doctrine of the Trinity, or the ‘trebling of the “oneness” of God’ (tathlīth waḥdāniyyat Allāh), as Yaḥyā put it.
The ground was prepared for these logical and philosophical discussions of the implications of the doctrine of at-tawḥīd by controversies that had arisen in the late eighth and early ninth centuries among Arabic-speaking Muslim theologians (al-mutakallimūn) on the one hand, and between Jewish, Christian, and Muslim theologians on the other hand, about the divine attributes (ṣifāt Allāh), the Quran’s ‘beautiful names’ (al-asmā’ al-ḥusnah) of God. For Muslims, the controversies had largely to do with how properly to understand the divine attributes recorded in the Quran in such a way that they neither implied anthropomorphism in God, nor compromised God’s ‘oneness’, even by implication (Gimaret 1988). For Arabic-speaking Christians, the controversies among Muslims about the divine attributes provided the Christian apologists both with an opportunity to develop a new theological approach with which to defend the credibility of their traditional doctrine of the Trinity, and with a new idiom in which to express the doctrine in Arabic (Griffith 2012). Their purpose was to argue in favour of the logical and religious credibility of trebling the ‘oneness’ of God (at-tathlīth), without in any way compromising the affirmation that God is truly one (at-tawḥīd) (see the studies included in Griffith 2000). As we shall see, not only did the Muslim mutakallimūn find this line of argument flawed and unconvincing, but from early in the ninth century onward Jewish scholars too argued that positing independently subsisting, essential attributes in the divine being compromised monotheism.
It is generally agreed among scholars that the distinctive mode of Islamic theology, the ‘ilm al-kalām (Frank 1992; see also Frank 1968; van Ess 1982), soon to be adapted to their own needs by Jews and Christians, grew up initially with the Muʿtazilite school of thought, responding to developments in the study of theoretical Arabic grammar and including elements of formal, largely Aristotelian logic provided by the contemporary translation movement (Frank 1978; Gimaret 1988). The Muʿtazilites flourished from the eighth century to the mid-ninth century, after which their school was eclipsed in official, Islamic circles by the so-called Asharite, Maturidite, and Ḥanbalite movements, most of whose ʿulamā nevertheless carried on in their works with the traditional methods of the ‘ilm al-kalām (van Ess 1991–7; Caspar 1987: 145–257. See also Watt 1998). The first generation of Christian mutakallimūn were contemporaries of the early Muʿtazilite mutakallimūn and the Christians composed their own kalām treatises much on the model of and often in the idiom of their Muslim counterparts, in an effort the more convincingly in their Islamic milieu to purchase a modicum of credibility for their own doctrines and to suggest the inadequacy, from the Christian point of view, of the current Islamic systems of thought (Griffith 2008a). There were similar developments mutatis mutandis in apologetic discourse among Arabic-speaking Jewish scholars in the same Baghdadī milieu, most notably in the work of Dāwūd ibn Marwān al-Muqammiṣ, who had at one time been an associate of a Christian mutakallim, Nonnus of Nisibis (Teule 2009). Al-Muqammiṣ’ major work, the ‘Ishrūn Maqālah, was largely an exercise in kalām against Christian teachings, including Christian ideas about the ‘oneness’ of God, as we shall see (Stroumsa 1989; Sklare 1999).
The Christian philosopher Yaḥyā ibn ʿAdī was heir to the earlier apologetic efforts of his own community’s mutakallimūn and he even wrote a number of apologetic texts of his own in the kalām style, in defence of the doctrine of the Trinity (Haddad 1985; Swanson 2005). He defended the doctrine against the strenuous objections of the early Muslim critic of religious doctrines, Abū ʿĪsā al-Warrāq (d. c.862; see Thomas 1996), whose text survives only in Yaḥyā’s transcription of it in the course of his refutation of its arguments (Thomas 1992; see also Platti 1991). Like the earlier apologists, Yaḥyā approached the subject within the framework of the ongoing discussion of the divine attributes. But in his response to the objections of al-Kindī, and in his discussion of the precise sense of the terms ‘the one’ and ‘oneness’, in dialogue with the thinking of his teacher al-Fārābī, Yaḥyā left the methods of the mutakallimūn behind, and he engaged in the discussion in terms of what he took to be the common idiom of Aristotelian logic.
The philosopher al-Kindī had said that he would challenge the Christians for the unreasonableness of their ‘trebling’ (at-tathlīth) the oneness of God on the basis of ‘logic and philosophy’, and more specifically, on the grounds that their Trinitarian confession necessarily involved the repulsive idea of introducing ‘composition’ (at-tarkīb) into the godhead. He said the following about the aqānīm/hypostases of the Christian Trinity, by which, he specified, ‘they mean “individual persons” (ashkhāṣ)’:
It is necessarily the case that each one of them is a composite of the substance which comprises them and of the particular property that particularizes it. Every composite is caused and nothing caused is eternal. Therefore, the Father is not eternal, nor is the Son eternal, nor is the Holy Spirit eternal. They are both eternal and not eternal; this is the ugliest absurdity. (Périer 1920–1: 4; Rashed and Jolivet 1998: II. 123)
In his response to al-Kindī, Yaḥyā argues that given the Muslim philosopher’s own description of God as simultaneously ‘God’ (ilāh), as ‘one’ (wāḥid), and as ‘substance’ (jawhar), al-Kindī too faced a logical conundrum involving the notions of ‘one’ and ‘three’. And Yaḥyā proceeds to find fault with al-Kindī’s use of the categories defined in Porphyry’s Eisagôgê to discredit the Christian doctrine, arguing that the Muslim philosopher had misunderstood and misused the technical terms involved when it came to his discussion of the Christian doctrinal formulas, but he overlooked the same difficulties involved in his own affirmations regarding the one God. In the end, according to Yaḥyā, the matter came down to the proper understanding of what one means when he predicates ‘one’ or ‘many’ of a subject. And he explains that God is said to be ‘one’ in number in reference to his ‘substance’/‘being’ (jawhar), while in reference to his ‘quiddity’ or ‘whatness’ (māhiyyah), which, according to Yaḥyā, is essentially described as being ‘generous/good’ (jawād), ‘wise’ (ḥakīm), and ‘powerful’ (qādir), he is ‘three’.5 This triad of predicates, Yaḥyā argues, bespeaks actual ‘meanings’ or essential ‘referents’ in God, each one of which differs from the other two (Périer 1920–1: 12–13; Wolfson 1976).
Yaḥyā follows much the same line of reasoning in his treatise on at-tawḥīd, in which he goes to considerable lengths to dispose of what he considers to be logically faulty definitions of ‘the one’ (al-wāḥid), such as those usually employed by Muslim thinkers, and then he explains what he regards as the proper understanding of the predicate ‘one’ in reference to God: the Creator is one by definition, in reference to his being the subject of the predications of the divine attributes; he is three in reference to the three essential attributes (ṣifāt) of his being, ‘goodness/generosity’ (jūd), ‘wisdom’ (ḥikma), and ‘power’ (qudra), the existence of which are, according to Yaḥyā, logically and ontologically prior to the predication of all other divine attributes (Samir 1980: 242–64).
In his response to Abū ʿĪṣā al-Warrāq’s criticism of the doctrine of the Trinity, and in another important essay in defence of the doctrine, Yaḥyā spoke of the three hypostases of the one divine being/substance in comparison with yet another exemplary triad that some in the Aristotelian tradition had also described as ‘one’, the intellect (al-ʿaql), ‘the subject of the act of intellection’ (al-ʿāqil), and ‘the object of the act of intellection’ (al-maʿqūl), a threesome that bespeaks yet another instance of Yaḥyā’s familiarity with earlier discussions of the ‘one’; his teacher al-Fārābī, as we shall see, critiqued this very idea in his On One and Unity (Platti 1991: 20–1; Périer 1920, esp. 11–27; Mahdi 1989: 55). In both of these instances, one sees Yaḥyā ibn ʿAdī’s turn away from the apologetic methodologies of the Muslim and Christian mutakallimūn of the preceding generations, while at the same time retaining their positioning of the problem of the Christian Trinity in terms of the current discussions about the ontological status of the divine attributes. The Christian mutakallimūn who preceded Yaḥyā had spoken of several different triads of divine attributes as composing what they proposed as the triad of essential divine attributes, bespeaking the corresponding essential referents in God, the existence of which, they had argued, is presumed for the predication of all other attributes.6 In his treatises, Yaḥyā consistently uses the two sets of triads just mentioned, preferring later in his career the triad: al-ʿaql, al-ʿāqil, and al-maʽqūl. The distinguishing feature of Yaḥyā’s triads is that unlike those that appear in the apologies of the mutakallimūn, both of his had their roots in the Aristotelian discussions of the First Cause and of the one and the many.
Thinking of himself as a logician who would go beyond the range of thought of the mutakallimūn, Yaḥyā ibn ʿAdī was determined to defend the credibility of the Christian doctrine of the Trinity in logical and philosophical terms, in the very idiom of the current philosophical discussion in the confraternity of the philosophers of tenth-century Baghdad about the meaning of predicating ‘one’ and ‘oneness’ of a subject. In this light one must turn then to a closer look at his Maqālah fī t-tawḥīd.
According to the scribal note at the head of the copy of Yaḥyā ibn ʿAdī’s Maqālah fī t-tawḥīd that is preserved in a seventeenth-century manuscript, he finished the work in the month of April, 940 ce (Samir 1980: 159), just ten years before the death of his teacher al-Fārābī (d. 950), during which time he, Yaḥyā, was presumably still very much under the influence of ‘the second master’ after Aristotle. But Sahban Khalifat has suggested that Yaḥyā may have composed this work in the light of his reading of the Aristotelian commentator Ammonius’ (c.435/445–517/526) Kitāb ḥujjat Arisṭāṭālīs fī t-tawḥīd (Khalifat 1988: 100). This first essay on at-tawḥīd is the earliest of a number of treatises in which over the following thirty years and more Yaḥyā would continue to develop his thought on the topic. It is instructive too to note at the outset that in the essay, unlike al-Fārābī who on the surface at least confined himself to the specifically philosophical and logical problems of ‘the one’ (al-wāḥid) and ‘oneness’ (al-waḥda), Yaḥyā immediately addressed himself to the topic in overt religious terms. He speaks up-front of how people differ about the meaning of what they affirm when they speak of the ‘oneness’ (waḥdāniyyah) of the Creator; Yaḥyā lists five examples, all of which he disowns as inadequate understandings when the subject is God.7 They include those who say that ‘oneness’ means to deny multiplicity of the Creator, or that he has no likeness (lā naḥʿīr lahu). Yaḥyā mentions one unnamed contemporary mutakallim, who is alleged to have said of the Creator’s ‘oneness’ that ‘its meaning, and that of the existence He has, is that He is one in the sense of being the starting point for numbering’.8 Then Yaḥyā mentions those who say that the meaning of ‘the one’ (al-wāḥid), when said of the Creator, is one (aḥad) of its meanings by which entities other than he are described. Finally there are those who say that the Creator is ‘one’ in every way, not multiple in any way, while others maintain that he is one in a certain way and multiple in another. As we shall see, Yaḥyā will later concede the validity of this position in the distinctive way in which he understands it. For now, he finds all of these understandings to be wanting in one way or another as their defenders uphold them, and he goes on to state his own purpose in writing his essay.
Our purpose in this essay is to examine these beliefs one by one, and by means of sound proofs and clear arguments to expose the falsity of the false and to elucidate the truth of the truthful, in the briefest and clearest way we can. (Samir 1980: 163–4; Khalifat 1988: 375–6)
True to his word, Yaḥyā ibn ʿAdī then sets about the relentlessly logical task of demonstrating to his own satisfaction that the foregoing five understandings of ‘oneness’ as predicated of the Creator that he had just described are all in some way inadequate and even invalid as their upholders explain them when it comes to speaking of the one God. To follow the long and often convoluted paths of his reasoning and argumentation would take us too far afield to rehearse them here. He says at the conclusion of the exercise that having shown the error of the adversaries’ definitions he must now set down what the real meaning of ‘the One’ is. He puts it this way: ‘We say “the One” is an existent being in which no otherness (ghayriyya) is to be found, whence it is one’ (Samir 1980: 196; Khalifat 1988: 384; Uluç and Argon 2008: 156). Yaḥyā goes on to detail the divisions of ‘one’ as so defined and then to describe the ways or modes (jihāt) of ‘one’ in the several divisions of its predication of a subject and to relate them to the corresponding divisions and modes of speaking of ‘the multiple’. This leads to his defence of the proposition that the Creator is rightly said to be ‘one’ (wāḥid) in one way of speaking and ‘multiple’ (kathīr) in another. While the Creator, or the ‘First Cause’, is ‘one’ in the sense that he is ‘an existent being in which no otherness is to be found’, according to Yaḥyā, he may also be said from another perspective to be ‘multiple’. And Yaḥyā goes on to argue that the one God may reasonably be said to be ‘multiple’ due to the fact that creatures, the caused effects of the Creator’s creation, are seen to bespeak the real presence of several states of being of the First Cause that Yaḥyā calls ‘meanings’ or ‘objective referents’ (maʿānī) of the ‘one’ Creator, or ‘descriptions’ (awṣāf, ṣifāt) of his ‘whatness/quiddity’ (māhiyya) that are more than ‘one’ and that are necessarily to be predicated of him as Creator. Yaḥyā reasons that these ‘meanings’, bespeaking objective referents in the divine essence, must logically be affirmed of the Creator’s very being as true in ‘act’ (fiʿl) as opposed to mere ‘potency’ or ‘power’ (quwwa); each must be affirmed as proper to God’s ‘essence’ (dhāt), as opposed to being predicated as an ‘accident’ (ʿarad); and each is affirmed in terms of its strict ‘definition’ (ḥadd), as opposed to being posited as a mere, non-essential ‘attribution’ (mawzūʿ). According to Yaḥyā, these essential ‘meanings’, ‘objective referents’, or ‘descriptive predicates’ bespeak ‘bountifulness’ (al-jūd), ‘active power’ (al-qudra), and ‘wisdom’ (al-ḥikma), as essential states of the divine being, ‘which are more than “one”, by means of which the First Cause and its “what-ness”, “quiddity” are to be described’ (Samir 1980: 242; Khalifat 1988: 398).
It is immediately evident that along with this line of reasoning, brought in toward the end of his essay, Yaḥyā has imported the technical terminology and the underlying grammatical premises of the discussions among the contemporary Muslim and Christian mutakallimūn about the ontological significance of the scriptural ‘divine attributes’ (ṣifāt Allāh), albeit that he presents his argument as a whole as a relentlessly logical and philosophical discussion about ‘the One’. In fact, the three essential states of God’s being that Yaḥyā argues must characterize the essence of the one God are the correlative states of being, bespoken by the ‘attributes’: jawād (jūd), qādir (qudrah), and ḥākim (ḥikma), the same triad of essential attributes he affirmed in his reply to al-Kindī mentioned above and in several others of his apologetic works. It is noteworthy that in the choice of these particular essential attributes, Yaḥyā is at odds with the varying triads of essential attributes normally proposed by earlier and contemporary Christian mutakallimūn, such as ‘existing’ (mawjūd), ‘living’ (ḥayy), and ‘rational’ (nāṭiq), without which they argued no others could reasonably be attributed (Haddad 1985: 218–22). Yaḥyā’s choice of these three notably Aristotelian attributes of the First Cause is seemingly dictated by his determination to appear relentlessly philosophical in his argument and to avoid any suspicion of being under the influence of the ʿilm al-kalām, albeit that he has nevertheless, perhaps unwittingly, brought in that discipline’s technical terms and grammatical assumptions about the necessary implications of predicating essential, descriptive attributes of God. After all, for Yaḥyā, as for the Christian mutakallimūn, the defence of the logical credibility of the Christian project of ‘trebling the oneness of God’ (tathlīth waḥdāniyyat Allāh) was the underlying reason for his logical defence of describing the Creator as simultaneously both ‘one’ and ‘multiple’, and for his argument that according to his definition of ‘one’, ‘the one’ comprises ‘the multiple’.
As for Yaḥyā’s rather negative definition of ‘the one’ as ‘an existent being in which no otherness is to be found, whence it is one’, it is clear that he was desperately trying to find a way to escape from the objection that even the positing of essential attributes of the one divine essence, one in being, entails notions of composition and quantity in some measure. As we shall see, the Jewish mutakallim al-Muqammiṣ had in the previous century already argued this very point in response to the allegations of the Christian mutakallimūn of his time that the essential attributes they predicated of God as indicative of the divine hypostases did not compromise God’s ‘oneness’ in being. And Yaḥyā clearly also wanted to find a way around al-Fārābī’s rejection of just such a line of reasoning as both the earlier Christian mutakallimūn and he, Yaḥyā, regularly employed in defence of the reasonableness of the doctrine of the Trinity. In the course of his descriptions of the ways in which the adjective ‘one’ might accurately be predicated of a subject, al-Fārābī had written as follows:
‘One’ may be predicated of anything, the quiddity of which is not divided by reason of a plurality of names and terms that are predicated of it, and the many terms concerning it do not refer to many ‘meanings’/referents (maʿānin), nor do the inflections of a single phoneme predicated of it refer to many transformations, on the pattern of what some people say, e.g., among many such, al-ʿaql, and al-ʿāqil, and al-maʿqūl, [saying that] the multiple inflections do not refer to multiple transformations within it. (Mahdi 1989: 54–5)
While al-Fārābī doubtless had other logicians in the Aristotelian tradition in mind with this observation, who would have been familiar with the traditional triad he cites, and not just the contemporary Christian mutakallimūn, his reasoning does nevertheless counter the very arguments these mutakallimūn customarily employed, including Yaḥyā, who, as we have mentioned above, had adopted this very triad as illustrative of the ontological status of the hypostases of the one God in his own treatises precisely because of its Aristotelian pedigree.
It is remarkable that Yaḥyā ibn ʿAdī concludes his Maqālah fī t-tawḥīd without ever explicitly mentioning the Christian doctrine of the Trinity, and without ever arguing, as he did in other texts, that the three essential attributes of the First Cause, i.e. the Creator, namely ‘bountifulness/goodness’, ‘power’, and ‘wisdom’, are indicative of the three ‘hypostases’ (aqānīm) of the one God according to Christian belief. But it is nevertheless crystal clear that a compulsion to explore the logical requirements for the reasonable affirmation of this very doctrine is what pressed Yaḥyā to propose his rather eccentric definition of ‘oneness’, and motivated his efforts to show how what is essentially ‘one’ on that definition, i.e. the First Cause, might also be seen logically to be ‘multiple’ by reason of the necessary ontological features that in his judgement must logically be predicated of the one essence of the one Creator or the First Cause, by reason of the very quiddity or ‘what-ness’ of the Creator, determined by the close observation of the Creator’s creatures, the products or effects of his creative actions and accomplishments.
It is clear that contemporary as well as latter-day readers of Yaḥyā’s essay had many difficulties with his reasoning. At some point after the completion of the text, he added an appendix in which he speaks of its reception among those who were studying it (Samir 1980: 266–72; Khalifat 1988: 404–6). He complains of people ignorant of logic and the rules of reasoning who, unable to discern the true meaning of words, mock and laugh at his work. He mentions those solicitous for the best science, equipped with the virtues of understanding, who nevertheless demean and disdain the positions he takes. He also mentions people who accept his reasoning who have no doubt or misgiving about it and deem it to be right. But given the length of the text, he worries about these readers’ grasp of the finer points. In the end, Yaḥyā says he wrote the appendix to caution readers not to be in too much of a hurry to make a decision about his reasoning, and not to make judgements on the basis of passing thoughts but to ponder and to think carefully about what he had written lest they too quickly neglect careful consideration and even-handedness in approaching his essay. The addition of the appendix therefore suggests that Yaḥyā’s Maqālah fī t-tawḥīd had already gained a wide circulation and that it had been subjected to criticism by his fellow logicians in the school of al-Fārābī and beyond.9
One can easily imagine how readily Yaḥyā’s non-Christian readers would recognize the special pleading he engaged in as he strove to define ‘one’ and ‘oneness’ in a philosophical way that would allow him without contradiction to affirm both ‘oneness’ and ‘three-ness’ of the one God. Indeed the Christian mutakallimūn before him and after him pursued the same elusive goal, usually working more in the vein of the ‘ilm al-kalām. But after Yaḥyā they more and more thought of themselves as purveyors of a philosophical theology. As for Yaḥyā himself, it is not unlikely that he thought he was taking al-Fārābī’s thinking about the ways in which something that is ‘one’ may also be said to be ‘many’ a step further than the master would have thought it could go. And Muslim apologists and polemicists, following in the wake of al-Kindī, continued to point out the errors in logic that they perceived in Christian reasoning such as Yaḥyā’s, beginning with those to whom he replied in the appendices to his Maqālah fī t-tawḥīd. Jewish scholars in the same milieu, from the ninth century onward had also been quick to take issue with such Christian efforts to treble the oneness of the one God, leading them as well to explore more fully the notion of oneness.
Writing probably already in the first half of the ninth century, the Jewish mutakallim Dāwūd ibn Marwān al-Muqammiṣ, who had for some time been under the tutelage of the Syriac-speaking Christian scholar Nonnus of Nisibis (d. after 862), had already taken up the question of what it means to say that God is one. In chapter 8 of his ‘Ishrūn Maqālah, al-Muqammiṣ provides what in the wider Baghdadī milieu may well be the earliest detailed discussion of what the word ‘one’ means for a monotheist (Stroumsa 1989: 164–72; Vajda 1967). Having reviewed six possible ways in which the term ‘one’ can be used; he concludes, recalling in the process the views of some other ‘monotheist scholars (al-ʿulamāʾ al-muwaḥḥida)’ as he calls them, that God is one in simplicity and one in both essence and act, and he says:
God is one in that there is no diversity in His essence, and one in that there is none equivalent to Him in His essence, and one in that there is none who is His peer or similar to Him in His act. (Stroumsa 1989: 172)
The ‘monotheist scholars’ whom al-Muqammiṣ mentioned in the lines just preceding this definition were in all probability Christians (Stroumsa 1989: 172 n. 60), a feature of the text that clearly bespeaks the inter-communal character of the discussion about God’s oneness already in early Abbasid times. Al-Muqammiṣ then turns to a somewhat detailed refutation of the trebling of the oneness of God as the Christian mutakallimūn in his milieu defended it (Stroumsa 1989: 172–83). He mentions their explanations of how the one God in one substance may be said to be simultaneously three hypostases/aqānīm without contradiction by offering analogies with created substances that can be said to be both three and one, such as three gold dinars with different inscriptions. He also mentions the kalāmic argument the Christian mutakallimūn employed, according to which the one divine substance may be said to be characterized by three essential ‘characteristic traits’ or ‘properties’ that are indicative of the three hypostases of the one God, thereby indicating his familiarity with the contemporary Christian defence of the reasonableness of the doctrine of the Trinity on the basis of their interpretation of the ontological significance of the divine attributes (ṣifāt Allāh), as was mentioned above. According to al-Muqammiṣ, neither the analogies nor the interpretation of the hypostases as three essential divine attributes can be logically defended because they inevitably involve additions of some sort to the one divine being of the one God, thereby compromising the notion of oneness.
Just about a century after al-Muqammiṣ’ time in Baghdad, Abū Yūsuf Yaʿqūb al-Qirqisānī (fl. c.940) also found it necessary in his discussion of the phrase in Deuteronomy 6: 4, ‘the Lord is one’, to expatiate on the meaning of the oneness thus affirmed of the one God. And in the process, with some adjustments, he appropriated al-Muqammiṣ’ earlier disquisition on the subject, listing six opinions of scholars on God’s oneness, highlighting in particular God’s simplicity, ‘He is one, not of a composite essence’, and the fact that there is none like him, ‘He is not an effect, but rather He is the cause of every effect’ (Ben-Shammai 1982). On this basis, elsewhere in his Kitāb al-anwār wal-marāqib Qirqisānī explicitly points out the logical inadequacies of the Christians’ explanations of the verisimilitude of their affirmation of the three hypostases/aqānīm of the one divine ‘being’/‘substance’ (jawhar), which they posit in view of their affirmation of God’s essential attributes, the absence of which they claim to be inconceivable. Qirqisānī argues very adroitly that the Christians base their arguments on logical principles, but he says that their definitions of such technical terms as jawhar, for example, are at variance with the definitions given by the ‘master of logic’ (ṣāḥib al-mantiq), who said that while it is true that a jawhar is a substance that exists on its own, as the Christians say, it is also by definition susceptible to supporting various, even contrary accidents in existence. If one then claims that God is a substance/jawhar, as the Christians do, this would logically lead to unacceptable conclusions such as introducing numbering into the divine essence, which in turn bespeaks composition, which then inevitably compromises ‘oneness’.10
Saʿadia ha-Gaʾōn (882–942) had likewise attacked the logic of Christian thinking in the matter of their defence of the doctrine of the Trinity on the basis of their positing the ontological priority and distinct individuality of select essential divine attributes that the Christian mutakallimūn argued must be subsistent in the one God’s very being, attributes (ṣifāt) such as ‘life’ (‘living’) and ‘knowledge’ (‘knowing’). Saʿadia argues that although elite Christians ‘maintain that they adopted their belief in the trinity as a result of rational speculation and subtle understanding’,11 their reasoning nevertheless logically and inevitably leads to the unacceptable supposition that God is a composite, physical being. It was undoubtedly pressure from well-reasoned critiques of Christian apologies for the doctrine of the Trinity such as Saʿadia’s that prompted Yaḥyā ibn ʿAdī to attempt to make a case for the reasonableness of the doctrine on the basis of a philosophical exploration of the meaning of ‘one’ and ‘oneness’, as he did in his Kitāb at-tawḥīd. But Moses Maimonides (1135–1204), looking back some 200 years later at the use Yaḥyā and other Christian thinkers made of Greek philosophy and logic to support the reasonableness of their religious convictions, found not philosophy in it but the beginnings of the ʿilm al-kalām. One can only imagine the chagrin that Yaḥyā would have felt at being classed by name among the mutakallimūn. As for Maimonides’ opinion of the efforts of the Arabic-speaking Christian apologists to defend the reasonableness of trebling the oneness of the one God on the basis of positing three essential attributes of God’s being, the author of The Guide of the Perplexed had the following to say.
If, however, you belong to those whose aspirations are directed to that high rank which is the rank of speculation, and to gaining certain knowledge with regard to God’s being One by virtue of a true Oneness, so that no composition whatever is to be found in Him and no possibility of division in any way whatever then you must know that He, may He be Exalted, has in no way and in no mode any essential attribute, and that just as it is impossible that He should be a body, it is also impossible that He should possess an essential attribute. If, however, someone believes that He is one, but possesses a certain number of essential attributes, he says in his words that He is one, but believes Him in his thought to be many. This resembles what the Christians say: namely, that He is one but also three, and that the three are one.12
Clearly in this retrospective view, albeit it was not his immediate purpose, Maimonides put his finger on the heart of the matter of the issue of ‘one’ and ‘oneness’, and confessing the ‘oneness’ of God as the issue was discussed in the milieu of Baghdad and its environs in the heyday of Abbasid intellectual culture. The topic engaged the attention of the intellectuals of all three monotheist communities at the very moment in early Islamic history when the stimulus of translated Greek philosophical and logical texts came to the fore in the Arabic-speaking scholarly milieu in which the implications of the newly explicated, theoretical Arabic grammar were already engaging the attention of religious thinkers anxious to explore the full meaning of the Arabic Quran.
This quick review of the discussions about the meaning of ‘one’ and ‘oneness’, especially as affirmed of the one God by Jews, Christians, and Muslims in Baghdad and its environs in Abbasid times, highlights the inter-communal character of intellectual life there at a crucial period in the development of Islamicate society. Philosophers and mutakallimūn of the several Abrahamic families of believers clearly developed their distinctive discourses in Arabic in tandem with and in reaction to one another, albeit that they seldom mentioned one another by name.13 Accordingly, it is crucial for an adequate study of the works of any one or several of them that the enquiry be made within the purview of the others, whose often contrary views and characteristic formulations would have been very much on the mind of any writer within a particular tradition who strove to present his own community’s views in counterpoint to those of his contemporaries who thought differently. Therefore any present-day study of the theological works of an Arabic-speaking, Jewish, Christian, or Muslim author of Abbasid times must for accuracy’s sake proceed with the awareness of the broader, even interreligious dimension of the author’s thought world. This was the case even in the most basic matter of confessing monotheism, the bottom line in Abrahamic faith. Arguably it was in the interreligious colloquies between Jews, Christians, and Muslims in Arabic-speaking Baghdad and environs in Abbasid times that the concept of monotheism received its most intense scrutiny prior to modern times.
1 Abū Naṣr al-Fārābī, Kitāb al-wāḥid wa l-waḥdah, ed. Mahdi (1989); Yaḥyā ibn ʿAdī, Maqālah fī t-tawḥīd, edited in Samir (1980) and in Khalifat (1988: 375–406).
2 In this connection, see Watt (2005; 2007). See also the earlier essays Allard (1962); Vajda (1962); Wasserstrom (1995).
3 Al-Kindī’s text, extracted from Yaḥyā’s treatise, is published independently, with discussion and a new French translation in Rashed and Jolivet (1998).
4 Samir (1980: 375–406). See the English translation of the first third of Yaḥyā’s essay, based on Khalifat’s edition, in Uluç and Argon (2008). The translation extends from p. 375 to the middle of p. 384 of Khalifat’s edition, omitting the final twenty-two pages, and two-thirds of the full text, albeit that n. 65 on p. 148 of the article would lead the unwary reader to think the entire text had been translated.
5 Yaḥyā seems to have been the first of the Arabic-speaking apologists for the doctrine of the Trinity to use this triad, with its roots in the Alexandrian philosophical tradition, in the Trinitarian context. See Haddad (1985: 218–22).
6 See the schematic presentation in Haddad (1985: 218–33).
7 Al-Fārābī too begins his On One and Unity with a discussion of the ways in which something is said to be ‘one’ and he goes on at considerable length to discuss the one and the many and the ways in which something may be said to be simultaneously one and many. See Mahdi (1989: 36–57, 75–97), concluding with an epitome of the ways in which something may rightly be said to be ‘one’, pp. 97–102.
8 Uluç and Argon render this difficult phrase as follows: ‘The meaning of the One and His existence is that He is One in the sense of being the beginning of numbers’ (Uluç and Argon 2008: 149).
9 An additional note is sometimes appended to Yaḥyā’s text in its Coptic transmission in which he offers a solution to the doubt that some readers of his essay had raised about his position that nothing exists without being qualified by some description or other that is a true description, thereby providing grounds for affirming that what is ‘one’ from one perspective may be seen as ‘multiple’ from another. The doubt was that this position ruled out the possibility of there being anything at all that could be said to be simply ‘one’ (wāḥid mufarrad). Yaḥyā’s solution was to point out that such a doubt arises only in the imagination of someone who thinks that what exists along with something else does not then exist itself. See Samir (1980: 273–7). This additional note is not published in Khalifat, The Philosophical Treatises (1988).
10 See in this connection, Yaʽqūb al-Qirqisānī, Kitāb al-anwār wal-marāqib; Code of Karaite Law, ed. Nemoy (1939), vol. I, III.2, 2–7, pp. 186–90.
11 Saʽadja b. Jûsuf al-Fajjûmî, Kitâb al-Amânât wa’l-Iʽtiqâdât, ed. Landauer (1880: 86), quoted in the English translation of Rosenblatt (1948: 103).
12 Moses Maimonides, The Guide of the Perplexed, trans. Pines (1963: I. 111).
13 An exception to prove the rule is Yaḥyā ibn ʿAdī’s reply to philosophical questions proposed to him by the Jewish scholar of Mosul in Iraq, Ibn Abī Saʾīd ʿUthmān al-Yahūdī, who sent his questions by the hand of one Bishr ibn Simsān ibn ʿUrs ibn ʿUthmān al-Yahūdī. See Pines (1955). The text is published in Khalifat (1988: 314–36). Yaḥyā also named the authors of works from which he quoted extensively for the purpose of refuting them, e.g. al-Kindī and Abū ʿĪṣā al-Warrāq, as mentioned above.