KINDĪ [Abū Yūsuf Yaʽqūb ibn Ishāq ul-Kindī, sometimes called pre-eminently “The Philosopher of the Arabs”] flourished in the 9th century, the exact dates of his birth and death being unknown. He was born in Kufa, where his father was governor under the Caliphs Mahdi and Harun al-Rashīd. His studies were made in Baṣra and Bagdad, and in the latter place he remained, occupying according to some a government position. In the orthodox reaction under Motawakkil, when all philosophy was suspect, his library was confiscated, but he himself seems to have escaped. His writings—like those of other Arabian philosophers—are encyclopaedic and are concerned with most of the sciences; they are said to have numbered over two hundred, but fewer than twenty are extant. Some of these were known in the middle ages, for Kindī is placed by Roger Bacon in the first rank after Ptolemy as a writer on optics. His work De Somniorum Visione was translated by Gerard of Cremona (q.v.) and another was published as De medicinarum compositarum gradibus investigandis Libellus (Strassburg, 1531). He was one of the earliest translators and commentators of Aristotle, but like Fārābī (q.v.) appears to have been superseded by Avicenna.