How do the heavenly bodies physically affect the sublunary world? On this topic, the few fragmentary statements by Aristotle were refined and expanded by his Greek commentator Alexander of Aphrodisias. In the Kindī-circle, particular attention was paid to Alexander's treatises on this very topic. They were not simply translated but were rather reworked in terms of an astrological interpretation. Typically, such reworking was attributed directly to Aristotle by the addition of a number of references and pseudo-references to Aristotle's genuine and spurious works. The article demonstrates this phenomenon, and examines the circular relationship between the Kindī-circle adaptations of Alexander and al-Kindī's own works. The Kindī-circle's Alexander was closely followed by al-Kindī on certain points, while al-Kindī himself exerted a reciprocal influence on the Arabic Alexander, who was largely the product of his own group of translators. The appendix contains English translations from Arabic of two adapted Alexander's treatises.

Al-Kindī contributed to the Arabic literature on methods of finding buried treasure. His short text on the subject has survived in two forms: a Letter, and a chapter of his astrological work known as The Forty Chapters. This article includes editions and translations of both these texts, as well as of the two Latin translations made of the chapter in The Forty Chapters and comments on the procedure advocated by al-Kindī.

Al-Kindī's Forty Chapters was one of the most influential astrological texts in the Middle Ages in the Arabic and Latin-reading world. Yet it has never been studied by modern scholars and has not even been properly identified in the standard bibliographies and encyclopaedias of Arabic literature. This study describes the work as it appears in the Arabic MS, Jerusalem, Khālidī Library, 21(2)-Astr.-2; sets it in the tradition of Greek, Persian and Arabic texts on catarchic astrology; and traces its influence on later Arabic astrological works, which give evidence of a fuller text than that in the Khālidī Library. This fuller text appears in the two Latin translations made in the mid-twelfth century by Hugo of Santalla and Robert of Ketton. Finally some comments are added about the place of The Forty Chapters in al-Kindī's œ;uvre. Two appendixes give respectively details of the manuscripts of the Arabic text and the two Latin translations, and an edition of a specimen chapter (concerning irrigation and cultivating the land) from these three versions.

With reference to my paper on the Apology of Al-Kindy, I have received the following letter from Professor Ignatius Guidi, dated Rome, 24th February:—

“You will he glad to hear that in the Propaganda Library (Museo Borgiani) I found a MS. of the Apology of Al-Kindî, together with the letter of his Moslem friend. The amanuensis was, I think, a Jacobite (the MS. is written in Karshuni character), hence he says (page 5, line 18 of the printed text):

The Roman MS. is apparently of the same family with the Paris MS. as described by Zotenberg, Catalogue des MSS. Syriaques de la Biblioth. Nationale, Nos. 204, 205.”

Al-Kindī's views concerning time are dispersed in different places in his works, but they are to be found principally in his On First Philosophy and De quinque essentiis (Sermo de tempore). Yes, he does follow Aristotle, but he insists on the homogeneity of the instant and of time; he also distances himself from the Philosopher by denying the eternity of the world a parte ante as well as a parte post. On the other hand, in his accounts of the realization of possible things and of the organization of the cosmos, he presents certain views that sometimes tend toward the principle of plenitude, and sometimes toward the doctrine of the best possible world, and here one can discern a principle that is distinctly theological.

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.

Al-Kindī was influenced by two Greek traditions in his attempts to explain vision, light and color. Most obviously, his works on optics are indebted to Euclid and, perhaps indirectly, to Ptolemy. But he also knew some works from the Aristotelian tradition that touch on the nature of color and vision. Al-Kindī explicitly rejects the Aristotelian account of vision in his De Aspectibus, and adopts a theory according to which we see by means of a visual ray emitted from the eye. But in the same work, al-Kindī draws on Philoponus’ commentary on Aristotle's De Anima. His borrowing from this commentary, via an Arabic paraphrase of the De Anima, was crucial in the development of al-Kindī's new ‘ ‘ punctiform analysis of light.” Conversely, two broadly Aristotelian works by al-Kindī, which explain the reason things are colored, engage with problems about color dealt with in the Aristotelian tradition ( e.g. by Alexander of Aphrodisias ). But here the Aristotelian theory, and in particular the Aristotelian notion of the transparent, is abandoned in order to accommodate the visual ray theory expounded in De Aspectibus.

Al Bîrûni, in his Vestiges of Ancient Nations, written A.D. 1000 (A.H. 390), while describing the customs of the Sabeans, cites the authority of Ibn Ishâc al Kindy, the Christian, in these words:

“Likewise Abd al Masîh ihn Ishâc al Kindy, the Christian, in his reply to the Epistle of Abdallah ibn Ismaîl al Hâshimy, relates of them (the Sabeans) that they are notorious for Human sacrifice, but that at present they are not able to practise openly the same.”

The autobiography witnesses a significant evolution in Avicenna's approach to Aristotle's Metaphysics during the years of his education. It clearly shows that, at a certain point of his philosophical training, Avicenna faced the entire text of the Metaphysics, was puzzled by its extent and complexity, and found in a treatise by al-Fārābī a guide for its understanding. But, albeit less perspicuously, the autobiography also suggests that this was not Avicenna's first encounter with the Metaphysics. Avicenna dealt with Aristotle's work in a previous stage of his studies as well. Then, however, he did not read the Metaphysics in its entirety, but, rather, focused only on its essential parts and some commentaries thereupon. The parts of the Metaphysics that Avicenna read in this earlier stage were books Alpha Elatton and Lambda, as constituting the natural theology of Aristotle's work. He neglected, on the contrary, the books corresponding to its ontological part. The special attention to Alpha Elatton and Lambda and the close connection between these two books in a theological context were peculiar traits of al-Kindī's approach to Aristotle's Metaphysics. Therefore, the evolving approach to Aristotle's Metaphysics that Avicenna's autobiography witnesses can properly be described as a passage from the Kindian to the Farabian way of interpretation.

After he wrote his well-known De aspectus, al-Kindī wrote a substantial critical commentary on Euclid's Optics: the “Rectification of error and difficulties due to Euclid's book: the Optics.” This previously ignored work enriches our knowledge of the optics not only of the geometers of the mid-9th century, but also of late antiquity. This is the first known commentary on Euclid's treatise, and it raises again the questions of its textual traditions, their multiplicity, and the role of Theon of Alexandria; it also poses the problem of the survival of al-Kindī's thought through his successors, such as Ahmad b. 'Īsā. The article examines these and related issues.