The authors translate and comment a digression from the Kitāb al-āṯār al-bāqiya on several hydraulic and hydrological subjects. The passage reveals al-Bīrūnī’s understanding of fluvial regimes, water physical behaviour, and of a handful of peculiar natural phenomena. Al-Bīrūnī departs from a discussion of weather forecast and seasonal fluvial regimes of the Tigris, Euphrates, Oxus, and Nile. The main concern of al-Bīrūnī is to defend the principle that water moves only downwards in absence of external forces. In doing so, the Khwarazmian scientist touches on the origin of salinity of the seas, the functioning of syphons related hydraulic machines, and relates a report of an artificial phenomenon, that he dismisses as result of faulty observations, that could be recognised as a hydraulic jump. In addition, the passage contains much relevant information on al-Bīrūnī’s understanding of the inhabitability of subequatorial regions, the possibility of the void, and the water cycle.

We study to what extent the Milky Way was used as an orientation tool at the beginning of the Islamic period covering the 8th to the 15th century, with a focus on the first half of that era. We compare the texts of three authors from three different periods and give detailed comments on their astronomical and traditional content. The text of al-Marzūqī summarises the information on the Milky Way put forward by the astronomer and geographer ʾAbū Ḥanīfa al-Dīnawarī. The text makes it clear that in some areas the Milky Way could be used as a geographical guide to determine the approximate direction toward a region on Earth or the direction of prayer. In the 15th century, the famous navigator Aḥmad b. Māǧid describes the Milky Way in his nautical instructions. He frequently demonstrates that the Milky Way serves as a guidance aid to find constellations and stars that are useful for precise navigation on land and at sea. On the other hand, Ibn Qutayba quotes in his description of the Milky Way a saying from the famous Bedouin poet Ḏū al-Rumma, which is also mentioned by al-Marzūqī. In this saying the Milky Way is used to indicate the hot summer times in which travelling the desert was particularly difficult. Hence, the Milky Way was useful for orientation in space and time and was used for agricultural and navigational purposes.

ʾAbū Saʿīd al-Siǧzī was a prominent fourth/tenth century astronomer and mathematician who was one of the first contributors to the new genre of ʿilm al-hayʾa (science of the configuration). However, little is known about the initial steps taken in the formation of the discipline, or its independence from other astronomical writings and practices. In this paper, I will discuss new findings about Siǧzī’s life to determine details of his biography and a more precise time period for his scientific activities. I then describe, for the first time, a composition in theoretical astronomy from the fourth/tenth century, the “Structure of the orbs” (Tarkīb al-aflāk) by Siǧzī to show its place in the formation of the discipline of ʿilm al-hayʾa, comparing Siǧzī’s book to the earlier work of al-Farġānī on the size of the earth and the number of celestial spheres. I conclude that Siǧzī’s Tarkīb al-aflāk is the earliest known example of a book that contains only topics found in later hayʾa and may be the first appearance of the ninth celestial orb that became standard in the later genre.

The famous philosopher and scientist Abū ʿAlī b. Sīnā (d. 428/1037) had an exceptional command of all the subjects on which he wrote. He is especially known for his many writings in logic, philosophy, and medicine. His influence was such that even in Europe, his works on physics, metaphysics and medicine in particular, were widely studied until the beginning of modern times. A keen mind, he had a full understanding of the inner structure of the Islamo-Hellenistic tradition that he perpetuated and in places helped to develop and reshape. This is not only borne out by his many writings, but in some instances also by his explicit accounts of the sciences and their divisions. This article contains an edition of one such account, of which only two copies have been identified so far. It will be argued (against Biesterfeldt) that the text in question is likely to have been written in Bukhārā when Avicenna was still in his early twenties. Moreover, it will be shown that it could very well be that the text was actually copied from his famous Al-ḥāṣil wal-maḥṣūl (Harvest reapings), a philosophical encyclopaedia in twenty volumes long since lost. The absence of algebra and a philosophical rather than a religious foundation of the sciences finally, are important clues to Avicenna's perspective on the rational sciences early in his career.

According to Avicenna, some of the objects of mathematics exist and some do not. Every existing mathematical object is a non-sensible connotational attribute of a physical object and can be perceived by the faculty of estimation. Non-existing mathematical objects can be represented and perceived by the faculty of imagination through separating and combining parts of the images of existing mathematical objects that are previously perceived by estimation. In any case, even non-existing mathematical objects should be considered as properties of material entities. They can never be grasped as fully immaterial entities. Avicenna believes that we cannot grasp any mathematical concepts unless we first have some specific perceptual experiences. It is only through the ineliminable and irreplaceable operation of the faculties of estimation and imagination upon some sensible data that we can grasp mathematical concepts. This shows that Avicenna endorses some sort of concept empiricism about mathematics.

A key work for the study of pre-modern Platonism, Galen's (d. ca. 217 CE) “Synopsis of Plato's Timaeus” (Com. Tim.) is served solely by an “imperfect” 1951 edition that presents for the first time the surviving Arabic text and translates it into Latin. The editors of the “Plato Arabus” series of the Corpus Platonicum, to which the edition belongs, blamed its flaws on the untimely death of Paul Kraus (1904-1944), who prepared the edition with another Jewish refugee Richard Walzer (1900-1975) around WWII. My analysis of archival sources will demonstrate that the labor on the volume was disproportionately Kraus’, whom Walzer and the Corpus Platonicum editor Raymond Klibansky (1905-2005) marginalized from the project in their attempts to secure employment in British academia as displaced Jews. I will also consider how Walzer and Klibansky re-envisioned Kraus’ plans for a Semitic corpus of Platonism to a narrower “Plato Arabus” that would align with a study of Latin Platonism (“Plato Latinus”) in which they presumed their British patrons would be more interested.

L'article propose une première approche systématique de la tradition manuscrite du Liber de causis, en étudiant à la fois les variantes manuscrites et les difficultés doctrinales suscitées par la translittération de l'arabe al-ʿaql conservée dans la traduction latine. Certains médiévaux (tel Albert le Grand) l'entendent comme un concept sans équivalent en latin, forgé par des philosophes arabes dont on ignore tout. D'autres médiévaux (tels Thomas d'Aquin et Gilles de Rome), qui ont probablement connu une branche différente de la tradition manuscrite du Liber de causis, n'en font aucune mention. En examinant cent dix manuscrits latins du Liber de causis (sur deux cent soixantecinq actuellement connus), on constate de nombreuses variations tant pour la présence de cette translittération dans les propositions du texte que pour les formes et les graphies (alatyr, alachili, adlahic, etc.). Cette analyse permet de comprendre tant la position d'Albert que la grande diversité, jusqu’à présent insoupçonnée, de la transmission du Liber de causis dans le monde latin.

Le fr. 2 de Boéthos de Sidon est transmis par deux commentateurs alexandrins des Catégories d'Aristote. En voici le texte grec:

[2a] Ioannes Philoponus, In Aristotelis Categorias commentarium, 5.15-20

Τρίτον ἦν ἐφεξῆς κεφάλαιον τὸ πόθεν δεῖ ἄρχεσθαι τῶν Ἀριστοτελι-[16]κῶν συγγραμμάτων. Βόηθος μὲν οὖν φησιν ὁ Σιδώνιος δεῖν ἀπὸ τῆς [17] φυσικῆς ἄρχεσθαι πραγματείας ἅτε ἡμῖν συνηθεστέρας καὶ γνωρίμου, δεῖν [18] δὲ ἀεὶ ἀπὸ τῶν σαφεστέρων ἄρχεσθαι καὶ γνωρίμων. ὁ δὲ τούτου δι-[19]δάσκαλος Ἀνδρόνικος ὁ Ῥόδιος ἀκριβέστερον ἐξετάζων ἔλεγε χρῆναι πρό-[20]τερον ἀπὸ τῆς λογικῆς ἄρχεσθαι, ἥτις περὶ τὴν ἀπόδειξιν καταγίνεται.

The Arabic text of Boethus fr. 44 Rashed has, pace Rashed (p. 266), a parallel in a Greek scholium to Galen's De elementis ex Hippocratis sententia. The scholium occurs in the sets of scholia to De elem. in Paris BNF suppl. gr. 634 (= Π; saec. xii) and in El Escorial Φ.II.15 (= Σ; saec. xiii). The former set was edited by G. Helmreich in Handschriftliche Studien zu Galen, vol. I. The relevant passage occurs in Π fol. 21 r ult. – v 3 (= schol. 34 p. 12 Helmr.) and in Σ fol. 136 r 7-11. The polysyllogism ascribed to Boethus reads: τὸ ὅμοιον ὑπὸ τοῦ ὁμοίου γινώσκεται. ἡ αἴσθησις τὰ στοιχεῖα γινώσκει. ἡ αἴσθησις ἄρα ὁμοία τοῖς στοιχείοις … ἡ αἴσθησις ὁμοία τοῖς στοιχείοις. τὸ ὅμοιον ἐκ τοῦ ὁμοίου [γινώσκεται]. ἡ αἴσθησις ἄρα ἐκ τῶν στοιχείων [γινώσκεται].

Dans le cadre des algorithmes numériques introduits et élaborés par les mathématiciens arabes, à partir du ixe siècle, figure l'algorithme de l'extraction de la racine carrée d'un entier naturel. Cet algorithme a été étudié chez plusieurs d'entre eux et surtout bien expliqué par alBaġdādī (mort vers 1037) dans le chapitre « Comment extraire la racine des nombres entiers » de son livre « La complétion du calcul », Al-takmila fī al-ḥisāb 1. Dans ce chapitre, al-Baġdādī expose son travail pédagogiquement en six sections traitant de plusieurs manières différentes le problème de l'extraction de la racine carrée d'un entier 2. À la même époque, dans un texte isolé intitulé « Sur la cause de la racine, de son doublement et de son déplacement 3 », Ibn al-Hayṯam (mort vers 1040) donne une justification géométrique de l'algorithme en se basant sur des notions algébriques précises.

That Ibn Sīnā’s “Canon of medicine” figures among the major classics of the history of medicine is doubted by no serious historian of medicine, eastern or western, Islamic or non-Islamic alike. It is therefore all the more surprising that so far no serious critical edition of this text was available. Certainly, a first, very timid step toward a really critical edition (published during the years 1982-1996) was made at the Institute of the History of Medicine and Medical Research (New Delhi), under the direction of Hakeem Abdul Hameed (1908-1999). It compared the four existing editions: Rome 1593; Būlāq (Cairo) 1877; Tehran (lithograph) 1878; and Lucknow 1905. In addition it used (a photocopy of) an ancient manuscript of Aya Sophia, dated 618, i. e. MS Aya Sophia 3686. With this new edition a further important step toward a full critical edition is made. Even if it is obvious that it does not yet present a “critical edition” in the full sense of the word, it has important merits.