Coming after Muʾayyad al-Dīn al-ʿUrḍī (1200–1266) and Naṣīr al-Dīn al-Ṭūsī (1201–1274), Quṭb al-Dīn al-Shīrāzī (1236–1311), a leading figure of the so-called Marāgha school in astronomy, presents his predecessors’ non-Ptolemaic models and criticizes them in his three hayʾa books. Since his own new models in Nihāyat al-idrāk (written in Arabic in 1281) and Ikhtiyārāt muẓaffarī (written in Persian in 1282) are not without difficulties, in his latest book on hayʾa, al-Tuḥfa al-shāhiyya (written in Arabic in 1285) he puts forward his modified models inspired from Ṭūsī’s and ʿUrḍī’s models and produces a series of new models for Mercury and the oscillation of the spheres. Nevertheless, in spite of all his attempts, the tradition of non-Ptolemaic modeling after him never converged to a series of standard models.

The “lost” Yaḥyā ibn ʿAdī treatises recently discovered in the Tehran codex Marwī 19 include a record of a philosophical debate instigated by the Ḥamdānid prince Sayf-al-Dawla. More precisely, Marwī 19 contains Yaḥyā’s adjudication of a dispute between an unnamed Opponent and Yaḥyā’s younger relative Ibrāhīm ibn ʿAdī (who also served as al-Fārābī’s assistant), along with Ibrāhīm's response to Yaḥyā’s adjudication, and Yaḥyā’s final word. At issue was a problem of Aristotelian exegesis: should “body” be understood as falling under the category of substance or under the category of quantity? The unnamed Opponent argues that body is a species of substance; Ibrāhīm argues that technically speaking, body is a species of quantity, and hence an accident; and Yaḥyā judges that body is a species of substance, though for very different reasons than the Opponent gives. For the first time, the Arabic text of this exchange is edited and translated into English. Also provided is an Introduction that sets the debate in historical context, and discusses in particular the possible influence of John Philoponus. The debate is interesting and important not only because of the philosophical ramifications of the issues under discussion, but because it constitutes evidence of dialectical practice among Arabic-speaking philosophers from the middle of the 10th century.

This article argues that a fragment from a lost treatise by Abū Bakr al-Rāzī (d. 925) is preserved in the Book on Morphology Kitāb al-Taṣrīf) by Ps-Ǧābir ibn Ḥayyān. Paul Kraus reached the conclusion that the collection to which this book belongs was written between the end of the ninth and the beginning of the tenth century AD. This fragment represents the first attempt – to our knowledge – to analyze the logical structure of sign-based inference in Arabic, which is known as istidlāl bi-al-šāhid ʿalā al-ġāʾib among theologians and philosophers. The author distinguishes between sign-inferences based on homogeneity (al-muǧānasa), course of habit (maǧrā al-ʿāda) and traces (āṯār). After providing a translation of the fragment, the first part of this paper argues that its author is Abū Bakr al-Rāzī. My argument is based on a comparison between this text and a passage from the Doubts About Galen, which is also by Abū Bakr al-Rāzī. I hypothesize that at least two other fragments from the same work or from different works by Abū Bakr al-Rāzī are preserved in the corpus attributed to Ps-Ǧābir. The second part of the paper aims to reconstruct Abū Bakr al-Rāzī’s theory of sign-inference. In so doing, I show the historical influence that Hellenistic debates on sign-inference might have had on al-Rāzī, and I situate al-Rāzī’s theory in the context of the prominent use that the theologians of the kalām made of the istidlāl bi-al-šāhid ʿalā al-ġāʾib. To offer a more comprehensive reconstruction of al-Rāzī’s theory of sign-inference, this article compares the critical approach presented in the newly identified fragment with the epistemological framework outlined in the Doubts About Galen. Finally, this article shows that Abū Bakr al-Rāzī’s theory of sign-inference had a strong influence on al-Fārābī’s logical developments especially in his Epitome of the Prior Analytics, even if he does not acknowledge this intellectual debt.

The twelfth century philosopher-theologian Fakhr al-Dīn al-Rāzī is well known for his critique of Avicennan metaphysics. In this paper, I examine his critique of Avicenna's physics, and in particular his rejection of the Avicennan and Aristotelian theory of place as the inner boundary of a containing body. Instead, Fakhr al-Dīn defends a definition of place as self-subsisting extension, an idea explicitly rejected by Aristotle and Avicenna after him. Especially in his late work, the Maṭālib, Fakhr al-Dīn explores a number of important philosophical issues with reference to this theory of place, including the principle that two indiscernible things (in this case two overlapping extensions) must be identical and the idea that motion and rest are always relative.

Avicenna's analysis of the definition of substance and accident repeatedly emphasizes two points: one and the same essence cannot be substance in one instance and accident in another; whether x is extrinsic or intrinsic for an underlying subject, y does not tell us anything as to whether x is substance or not. Both points are development in an argument against certain unnamed people who claimed the opposite. In this article I will show that Avicenna's opponents are to be identified with the mainstream Baghdad Peripatetic School (Ibn Suwār, Ibn al-Ṭayyib) which based itself on the Late Antique rule that “parts of substances are substances”. As for Avicenna's own position, it was developed on the basis of the heterodox position of Yaḥyā b. ʿAdī, who anticipated Avicenna's first point. This is a further piece of evidence for something that has only recently begun to be appreciated: the influence of Ibn ʿAdī on Avicenna.

Abū Bakr al-Rāzī (d. 925) and al-Fārābī (d. 950) both adopt the classical ideal of a philosophical way of life in the sense that being a philosopher implies certain ethical guidelines to which the philosopher should adhere. In both cases, moreover, their ethical writings appear to reflect a certain tension with respect to what the ethical goal of the philosopher consists of. In this study, I will argue that this apparent tension is relieved when their ethics is understood as a progression in a double sense. In the first sense, both authors adopt the Neoplatonic distinction between pre-philosophical and philosophical ethics. The second aspect of the progression takes place within the degree of virtue required of the philosopher, which for al-Rāzī and al-Fārābī proceeds in contrary directions. For al-Rāzī, the philosopher progresses from the moderately ascetic requirements of Spiritual Medicine to the higher license present in Philosophical Life, following the stages of the life of Socrates. In contrast, for al-Fārābī the progression follows roughly along the Neoplatonic grades of virtue from Aristotelian moderation, which in Exhortation to the Way to Happiness is connected with character training in a pre-philosophical sense, towards purely contemplative existence.

This study investigates the problem of the natural universal (kullī ṭabīʿī) in the works of Mullā Ṣadrā (d. 1640). The problem of universals made its way into Arabic/Islamic philosophy via its Greek sources, and was transformed into the problem of natural universals by Avicenna. Weighing in on this problem, Ṣadrā reinterprets the nature of natural universals against the backdrop of his doctrine of “the primacy of being.” As he argues, a natural universal or quiddity qua quiddity is an “accidental being” that requires wujūd for its existentiation. Thus, Ṣadrā re-envisions the status of natural universals by stripping them of their disputed status as independently existing entities.

It is known that Fārābī, in his political program, assumes philosophically some Islamic sciences like kalām and fiqh. Focusing here on the case of the fiqh and in the limits of his K. al-Milla, we try to establish correspondences between his theory of legislation and references to historically attested sciences. Our purpose is to show that he was able to articulate fiqh to the political science through an undeclared use of ʿilm uṣūl al-fiqh (science of principles of juridical science). He empties this science of its own material and preserves its form in order to fill it with philosophical material. This contributes to clear up his conception in this book of the shift from the voluntary universal to the particular. This shift is governed by a set of formal rules. These guidelines, which are rather deliberative, take place as a subject matter of the political science, alongside with universals, its classical subject matter. We think that these formal rules are borrowed from this typical Islamic science whose subject matter is the study of principles and rules governing the inference, from their sources, of particular legal status, the subject matter of fiqh. If, from the strict philosophical point of view, political science provides the sources or foundations from which are inferred the original and primary legislation initiated by the founder of the religion (al-milla), as well as the derived and secondary one elaborated by his successors, the methodological part of this Islamic science would be the equivalent to the general prescriptions necessary for the application of universals so that concrete cases can be determined. For this purpose, Fārābī borrows willingly from the famous Shāfiʿī’s Risāla, the prototype of the treatises in uṣūl al-fiqh.