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.

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.

Averroes wrote three kinds of commentaries on the books of Aristotle - epitomes, middle commentaries, and long commentaries - and each kind had its own purposes. His aims may have also differed from text to text. That is, it seems reasonable to assume that he would stick closer to Aristotle in the logical works than, for example, in the metaphysical works. The present study investigates what may be called the “theological aspects” of Averroes' commentaries, and explores the commentary of Averroes that appears least likely to contain such elements, the Middle Commentary on the Prior Analytics. The Prior Analytics is perhaps the most straightforward, even pedantic, of all of Aristotle's writings, and of Averroes' three kinds of commentaries, it is the middle commentaries which are least likely to diverge or digress from the text of Aristotle. The only trace of a religious hand in the commentary is Averroes' use of examples, and, in particular, examples that conclude that “the world is created” and the like. It is argued that Averroes chose these examples to show the traditionalist reading public the falsity of the theologians claims against the logic of the philosophers. The Appendix to the article shows that medieval commentators on Averroes' commentaries were also struck by his “creation of the world” examples.

The stages in the development of Averroes' philosophy can be better defined by the revisions Averroes himself made of his works than by the traditional order of his commentaries (short, middle, long); such revisions often take the form of glosses. In his initial stages Averroes' opinions are influenced by the interpretations of Alexander of Aphrodisias and Themistius as well as Avempace. In his final stages, he departs from them and moves closer to Aristotle's original thought. Averroes' reading of the beginning of Physics, Book VIII is an exception: there he agrees with Aristotle in the first stage and moves away from him in the final stage, because he came to believe that Aristotle's purpose in this part of the book was to prove the eternity of heavenly movement. The explanation for the different reading of the introduction to the short commentary can be found in the persecution Averroes and other philosophers suffered in 1197, after which Averroes no longer declared philosophy to be the way to attain human perfection, and he only wanted to illuminate Aristotle's philosophy.

Where Averroes' commentaries on Aristotle can be dated, the Middle Commentary on a given work can be seen to predate the Long Commentary. As an accompaniment to his fine edition of Averroes' Middle Commentary on the De anima, A. Ivry has maintained that in this instance matters are reversed and the Middle Commentary on the De anima is “an abridged and revised version” of the Long Commentary on the same work. Ivry develops his thesis most fully in Arabic Sciences and Philosophy 5. There he argues that two passages in the Middle Commentary on the De anima refer to the Long Commentary by name, that a third passage alludes to the Long Commentary, and that in other passages the Middle and Long Commentaries use similar phraseology and the former can be seen to have abridged the latter. The present article replies as follows: The pair of passages in the Middle Commentary which Ivry reads as referring explicitly to the Long Commentary can plausibly be read as cross-references within the Middle Commentary itself. The passage that he takes as alluding to the Long Commentary does not in fact allude to that work, but is an unambiguous reference to a later section of the Middle Commentary. And there is no justification for regarding the passages in the Middle Commentary cited by Ivry which use phraseology similar to that of the Long Commentary as borrowings from the latter. In the course of his arguments, Ivry refers to Averroes' position on the nature of the human material intellect, the issue that gave Averroes the most trouble in his commentaries on Aristotle's De anima and that has most intrigued students of Averroes ever since. The present article points out that on the subject of the human material intellect, neither the Middle nor the Long Commentary on the De anima borrows from the other, for the conceptions of the material intellect which they espouse are different and incompatible.

Herbert Davidson's critique of my thesis regarding the relation between Averroes' Middle and Long commentaries on De anima contrasts my reading and translation of Middle Commentary passages with his own. I leave it to the informed reader to judge whether one translation is more “neutral” than the other, excluding the specific denotation which I give to sharh, which is the point at issue.