Most scholars of Islamic intellectual history now agree on the distortedness of the traditional Western portrayal of al-Ġazālī (d. 1111) as the defender of Muslim orthodoxy whose Incoherence of the Philosophers (Tahāfut al-falāsifa) was such a powerful critique that it caused the annihilation of philosophical activity in Islamic civilization. Some in fact are coming to the conclusion that al-Ġazālī's importance in the history of Islamic philosophy and theology derives as much from his assiduous incorporation of basic metaphysical ideas into central doctrines of Sunnī kalām, as from his far more celebrated bashing of the falāsifa. What is less well known is that al-Ġazālī's role in the ‘‘philosophizing” of Sunnī theology was not a lonely struggle by a single genius, but part of a broader trend that seems to have begun during Avicenna’s lifetime and that picked up speed in the first and second generations after Avicenna's death in 1037, with the work of al-Ġazālī's teacher, the Aš‘arite al-Gˇuwaynī (d. 1085), as well as of the Māturīdite al-Bazdawī (d. 1099), work that was carried forward by dozens of subsequent members of those two major Sunnī theological schools. It is clear, in fact, that the dividing line between the Sunnī theologians commonly referred to in the later Islamic tradition as mutaqaddimūn (‘‘early” or ‘‘ancient”), and those referred to as muta’aḫhḫirūn (‘‘late” or ‘‘modern”), lies not with al-Ġazālī but with Avicenna himself, and that the turn in Sunnī kalām was therefore Avicennian, not Ġazālian.

According to Tāj al-Dīn al-Subkī (d. 771 / 1370), al-Ghazālī (d. 505 / 1111) was the renewer (mujaddid) of the Muslim faith at the end of the 5th / 11th century, whereas al-Rāzī (d. 606 /1210) was the renewer of faith at the end of the 6th / 12th century. That al-Ghazālī deserves such an honour can hardly be disputed, and his importance in the history of Islamic thought is generally recognised. However, the same cannot, as easily, be said of al-Rāzī, whose historical significance is far from being truly appreciated, and some of the most important books of whom still await publication. Much is known about his views on particular philosophical and theological problems, and about the historical backgrounds to, and the relations amongst, some of these views. Some rather general observations on his thought are also common; for instance, that he is a heavily philosophising Ash‘arī mutakallim, a master dialectician, and an influential critic of Ibn Sīnā.

The concept of ‘‘certitude” (yaqīn) is central in Arabic discussions of the theory of demonstration advanced by Aristotle in the Posterior Analytics. In the Arabic tradition it is ‘‘certitude,” rather than ‘‘knowledge” (‘ilm=Greek epistēmē), that is usually identified as the end sought by demonstrations. Al-Fārābī himself devotes a short treatise, known as the Conditions of Certitude (šarā’iṭ al-yaqīn), to determining the criteria according to which a subject can claim to have absolute certitude of any proposition. In this article the author traces the roots of the concept of certitude to the Arabic translation of the Posterior Analytics. She then offers a close reading of the text of al-Fārābī's Conditions and its parallels in his Epitome of the Posterior Analytics (Kitāb al-Burhān). She argues that the identification of certitude as a cognitive state distinct from knowledge enabled al-Fārābī to introduce a number of interesting and sometimes problematic innovations into Arabic epistemology. Foremost amongst his positive innovations is the recognition that contingent as well as necessary propositions allow for an attenuated form of certitude, and the introduction of reliabilism into the justification of claims to certitude. But al-Fārābī is also one of the first philosophers to articulate explicitly the idea that certitude must include an element of ‘‘knowing that one knows,” a controversial principle that tends to undermine both al-Fārābī’s reliabilism and his efforts to loosen some of the strictures in traditional Aristotelian epistemology.

Ancient Peripatetics and Neoplatonists had great difficulty coming up with a consistent, interpretatively reasonable, and empirically adequate Aristotelian theory of complete mixture or complexion. I explain some of the main problems, with special attention to authors with whom Avicenna was familiar. I then show how Avicenna used a new doctrine of the occultness of substantial form (whose roots are found in Alfarabi) to address these problems. The result was in some respects an improvement, but it also gave rise to a new set of problems, which were later to prove fateful in the history of early modern philosophy.

First century Chinese, fifth century Indian, and Arabic documents from the 9th century onwards, contain similar tabular procedures to extract square and cube roots on place-value numeration systems. Moreover, an 11th century Chinese astronomer, Jia Xian, as well as al-Samaw'al, a 12th century Arab mathematician, extracted roots of higher order with the so-called Ruffini-Horner procedure. This article attempts to define a textual method to organize this corpus, by distinguishing relevant criteria for identifying similarities and differences from a historical as well as conceptual point of view. The first part analyses three different states of the descriptions of algorithms in China between the 1st and the 11th centuries, all of which exhibit a definite historical stability. The rewriting which allows one to proceed progressively from one state to the next shows a uniformity in the components of the algorithm, which culminates in procedures of the type Ruffini-Horner. Textual criteria demonstrate a greater affinity of certain algorithms, such as those described by Kūshyār ibn Labbān (ca 1000) with Chinese rather than with Indian texts, which are in turn closer to algorithms described by al-Khwārizmī. Criteria of the same kind link the algorithms of Jia Xian and al-Samaw'al on the one hand, and those of Kūshyār and al-Samaw'al on the other.

Although numerous studies have been conducted on the Optics (Kitāb al-Manāzir) of Alhazen (al-Hasan ibn al-Haytham, d. 1040 C.E.), and on its reception, assimilation and maturation within the course of development of the perspectivae traditions in the history of science and art, ambiguities do hitherto still surround the epistemological and ontological entailments of his theory of visual perception. In addressing this question, our inquiry herein is principally philosophical in scope and our textual reading combines exegesis with hermeneutics. While we observe the delicate procedures of historiography and philology, we do not unguardedly assume that they are exhaustive of all rigorous methods of thoughtful investigation. Moreover, in heeding the internal coherence of Alhazen's text, we do not simply lock his views within reductive contextual chronologies, or readily confine them to epochal matters of textual transmission. Our endeavour is therefore not exclusively set in view of serving the purposes of archival documentation, even if we preserve a thorough and sound sense of historicity. We ultimately recognize the philosophical pertinence of numerous subtle leitmotifs within Alhazen's thinking that speak to us in an effective timely manner, which is significantly relevant in its attuned bearings to the thrust of phenomenological theories of perception.

As for Avicenna the human soul is a complete substance which does not inhere in the body nor is imprinted in it, asserting its survival after the death of the body seems easy. Yet, he needs the body to explain its individuation. The paper analyzes Avicenna's arguments in the De anima sections, V, 3 & 4, of the Shifā' in order to explore the exact causal relation there is between the human soul and its body and confronts these arguments with relevant passages in the Metaphysics. It argues that the causal relation between body and soul remains obscure and that, though Avicenna claims that there is a personal immortality and that the disembodied soul remains individuated, he does not provide a satisfactory ontological account for it.

The traditional argument of Muslim theologians that aims to verify the claims of a true prophet and distinguish him from an impostor is based on the acceptance of miracles performed in history and testified through an uninterrupted chain of tradition (tawātur). A second argument that equally involves transmission through tawātur is based on the prophet’s virtuous and impeccable character establishing the trustworthiness (sidq) of the prophet. These are, for instance, the types of proofs (singl. huˇgˇga) mentioned by the Baghdadian Mu‘tazilī al-Gˇāhiz (d. 255/869) in his monograph Huˇgaˇg al-nubuwwa. For theologians of the Aš‘arite school this approach to the verification of prophecy posed a problem. According to classical Aš‘arite theology, good is what God commands and bad is what he forbids. If God chooses prophets to reveal knowledge about what is right and what is wrong, and thus also reveal knowledge about how to live a virtuous life, how can those whom the prophets call upon know that the prophets have a virtuous character before they even know the criteria for virtue? Early Aš‘arite theologians indeed accepted that all prophets had a most virtuous character. This fact, however, became apparent only after their message gained acceptance within their community and it cannot be regarded as a viable verification of the claim of a prophet to those he calls upon. Al-Aš‘arī (d. 324/935), for instance, is said to have accepted a number of indications that allow humans to distinguish a prophet from ordinary people. He does not mention the claim based on the impeccable moral conduct of prophets. In fact, he stresses that in order to distinguish a true prophet from other people who are close to God (awliyā'), but who have no message to reveal, one should put oneÕs trust only in the occurrence of true prophetic miracles.

Abraham ibn Ezra the Spaniard (d. 1167) was one of the foremost transmitters of Arabic science to the West. His astrological and astronomical works, written in Hebrew and later translated into Latin, were considered authoritative by many medieval Jewish and Christian scholars. Some of the works he translated from Arabic are no longer extant in their original form, and on occasion his treatises provide information about earlier sources that is otherwise poorly preserved, if at all. Ibn Ezra seems to be the earliest scholar to record one of the seven methods for setting up the astrological houses, and this method was subsequently used by Levi ben Gerson (d. 1344) in southern France.

The paper discusses al-Kindī's response to doctrines held by contemporary theologians of the Mu‘tazilite school: divine attributes, creation, and freedom. In the first section it is argued that, despite his broadly negative theology, al-Kindī recognizes a special kind of “essential” positive attribute belonging to God. The second section argues that al-Kindī agreed with the Mu‘tazila in holding that something may not yet exist but still be an object of God's knowledge and power (as the Mu‘tazila put it, that “non-being” is a “thing”). Also it presents a new parallel between al-Kindī and John Philoponus. The third section gives an interpretation of al-Kindī as a compatibilist, in other words as holding that humans may be free even though their actions are necessitated. In all three cases, it is argued, al-Kindī is close to the Mu‘tazilite point of view, though he departs from them in the arguments he gives for that point of view.

This paper surveys the results established so far by the on-going research on the planetary theories in Arabic astronomy. The most important results of the Maragha astronomers are gathered here for the first time, and new areas for future research are delineated. The conclusions reached demonstrate that the Arabic astronomical works mentioned here not only elaborate the connection between Arabic astronomy and Copernicus, but also that such activities, namely the continuous reformulation of Greek astronomy, were not limited to a specific group of astronomers or to a specific geographical area. It is shown that such activities were spread over a period of more than seven hundred years, from the early eleventh till the sixteenth century, and over an area stretching from the Andalusian peninsula in the west to the farthest reaches of Central Asia in the east.

In this paper, are included new data about three treatises ascribed in Arabic to Alexander of Aphrodisias. These treatises were thought to have no Greek correspondent. The author shows that one of them, (D.8a), is an adapted version – following the norms of “al-Kindi circle” – of Quaestio I 21, along with the later and more exact version of this Quaestio by Abū ‘Uṭmān al-Dimašqi (d. 900). He shows also that the two other treatises (D.9 and D.16) are, in contradistinction to the first, adapted versions of passages belonging in the De Aeternitate mundi contra Proclum of John Philoponus: respectively IV, 4–6 and IX, 11. Philoponus’ book was known to have been translated, into Arabic. But, except for some short fragments in al-Bīrūnī (d. 1048), it seems that it is the first time that important adapted extracts of it are put in light. Some points are made about the historical position of the epitomator of these passages. In Appendix II, another treatise ascribed to Alexander (D.27g) appears – provisionally – as a composite text, mixing elements coming from Philoponus and others from neoplatonic texts in Arabic. In Appendix III is analysed the use of D.16 by Miskawayh (d. 1030), and the use of D.27g by ‘Abdallaṭīf al-Baġdādī (d. 1231).

Our intention here is to present the essential character of classical, sunnī kalām within a strictly formal perspective and to set out its basic aspects. It was conceived by the mutakallimīn as a rational, conceptual, and critical science and, although kalām differed in a number of basic concepts and constructs and in its analytic system, the topical organisation of the major compendia parallels that of metaphysics as understood in the contemporary Aristotelian tradition. The debates between kalām and falsafa need to be examined within this context. Kalām, however, is theological in the strict sense of the term and it is as such that its problematic and its procedures are primarily to be understood. Thus seen, the object of kalām is to rationalise the cognitive content presented to Believers in the symbolic language of the koranic revelation. It has, then, four principal tasks, sc, to conceptualise, to order, to explain, and where possible to justify the primary doctrines of the community whose belief is held to be normative. Within this framework the differences that characterise the major schools as such and the various tendencies of individual masters within each school may readily be brought to light.

For many centuries Jews in Arabic-speaking lands have transcribed books written by non-Jews into the Hebrew alphabet; the language remains Arabic, but the writing is Hebrew. This was done mainly for the benefit of those who knew the Arabic language but not the script. The majority of these transcriptions are scientific or philosophical texts. Transcriptions are of value to scholars for two reasons. Some entire texts, or more complete or accurate versions of texts, are preserved only in transcription. In addition, the choice of texts transcribed is very instructive concerning the cultural and intellectual interests of Jews. A century ago the great bibliographer Moritz Steinschneider published a description of the transcriptions known to him. We have undertaken to prepare a full catalogue. In this article we offer a preliminary relisting of those manuscripts that we have examined recently.

Ibn al-Bannā' of Marrakesh (1256–1321) is the author of one of the four extant “editions” of the unfinished zīj of Ibn Isḥāq (fl. Tunis and Marrakesh ca. 1193–1222): it contains a selection of his tables accompanied by a collection of canons, easy to understand, which makes the zīj accessible for the computation of planetary longitudes. The present paper studies some modifications of the structure of the tables the purpose of which is to make calculations easier. The tables of the planetary and lunar equations of the centre are “displaced." The tables of the equation of the anomaly of Mars, Venus and Mercury, are standard, while, in the cases of Jupiter and Saturn, the equation of the anomaly is calculated in the same way as that for the Moon. Ibn al-Bannā' appears as a clever adapter, who displays a clear ingenuity allowing him to introduce formal modifications which give his work an appearance of novelty which does not correspond to reality.

This paper investigates the objections that were raised by the philosopher ‘Abd al-Laṭīf al-Baghdādī (d. ca. 1231 CE) against al-Ḥasan ibn al-Haytham’s (Alhazen; d. after 1041 CE) geometrisation of place. In this line of enquiry, I contrast the philosophical propositions that were advanced by al-Baghdādī in his tract: Fī al-Radd ‘alā Ibn al-Haytham fī al-makān (A refutation of Ibn al-Haytham’s place), with the geometrical demonstrations that Ibn al-Haytham presented in his groundbreaking treatise: Qawl fī al-Makān (Discourse on place). In examining the particulars of al-Baghdādī’s fragile defence of Aristotle’s definition of topos as delineated in Book IV of the Physics, which was rejected on mathematical grounds by Ibn al-Haytham, a special attention is also given to highlighting the systemic distinctions between the entities that are studied within the speculative physical doctrines of common sense and immediate experience, and the postulated ‘objects’ of scientific and mathematical research.

Al-Fārābī, in the Kitāb al-Ḥurūf, is apparently the first person to maintain that existence, in one of its senses, is a second-order concept [ma‘qūl thānī]. As he interprets Metaphysics Δ7, ‘‘being'' [mawjūd] has two meanings, second-order ‘‘being as truth'' (including existence as well as propositional truth), and first-order ‘‘being as divided into the categories.'' The paronymous form of the Arabic word ‘‘mawjūd'' suggests that things exist through some existence [wujūd] distinct from their essences: for al-Kindī, God is such a wujūd of all things. Against this, al-Fārābī argues that existence as divided into the categories is real but identical with the essence of the existing thing, and that existence as truth is extrinsic to the essence but non-real (being merely the fact that some concept is instantiated). The Ḥurūf tries to reconstruct the logical syntax of syncategorematic or transcendental concepts such as being, which are often expressed in misleading grammatical forms. Al-Fārābī thinks that Greek more appropriately expressed many such concepts, including being, by particles rather than nouns or verbs; he takes Metaphysics Δ to be discussing the meanings of such particles (comparable to the logical constants of an ideal language), and he takes these concepts to demarcate the domain of metaphysics. This explains how al-Fārābī's title can mean both ‘‘Book of Particles'' and ‘‘Aristotle's Metaphysics.''

In this article we study the development of the mathematical theorem, now known as the Tūsī Couple, and discuss the difference between its plane and spherical applications.

One of the epistemological results emerging from this initial study is that the different forms of co-relational inference, known in the Islamic jurisprudence as qiyās, represent an innovative and sophisticated form of reasoning that not only provides new epistemological insights into legal reasoning in general but also furnishes a fine-grained pattern for parallel reasoning which can be deployed in a wide range of problem-solving contexts and does not seem to reduce to the standard forms of analogical argumentation studied in contemporary philosophy of science. However, in the present paper we will only discuss the case of so-called co-relational inferences of the occasioning factor and only in the context of Islamic jurisprudence.

In the absence of the Arabic text of al-Khwārizmī's Arithmetic (ca. 825), which has not yet been found, the oldest Latin adaptations from the twelfth century are the only evidence documenting the genesis and the first spreading of a decimal arithmetic that uses nine figures and zero, i.e. the Indian reckoning known in the Middle Ages as algorismus. This paper studies these texts, their content, their sources, and identifies their authors and the milieus in which they were written.