THAT there existed an Arabic translation of the commentary of Themistius on the De Anima of Aristotle has long been known through the references made to it in the works of Ibn Rushd.1 The commentary itself is mentioned by Ibn al-Nadīm in the Fihrist.2 In his note on the De Anima he says: ‘ Themistius wrote a commentary on the whole of this work. He dealt with the first section in two sections, the second in two, and the third in three ’—a division which corresponds to that of the Greek text as we have it. Unfortunately, on the subject of the translation, Ibn al-Nadim's article is not without ambiguity. According to it, Hunain ibn Ishāq translated the entire De Anima into Syriac, while his son, Ishāq, translated the greater part of it into Arabic, and then made a second and complete translation. Ibn al-Nadīm proceeds to quote Ishāq himself as saying: ‘ I translated this work into Arabic from a defective manuscript. Then, after thirty years, I found an extremely good manuscript with which I collated my first version’. The quotation ends with the words: ‘ and it is the commentary of Themistius ’.