The commentary Thomas Aquinas completed on Aristotle's 'De Anima' is thought to be the first of some dozen such commentaries that he wrote toward the end of his short career. He may have produced the work in 1268 while teaching in the Dominican house of Santa Sabina in Rome. Shortly thereafter he returned to Paris where he swept into the Latin Averroist controversy, at the centre of which was the proper interpretation of the De Anima. Avicenna and Averroes, the great Arabic commentators, read the 'De Anima' in such a way that intellect was taken to be a separate substance and not a faculty of the human soul. Some of Thomas's contemporaries, Masters of the Faculty of Arts, accepted the Avicennian and Averroist interpretations as good money and thus came to old positions incompatible with their Christian faith. What is the correct reading of the 'De Anima'? This commentary, composed before Thomas was caught up in the contemporary controversy, sets out to understand what it is that the text teaches. Many students of Aristotle have come to see this commentary as indespensible to reading the text aright.