The Commentary of St. Thomas
on the De caelo of Aristotle
The “commentary” or Sententia De caelo et mundo of St. Thomas is a work of great maturity and profundity. It is one of Thomas's last writings, and it reveals a breadth of scholarship and achievement wanting, for the most part, in his earlier Aristotelian commentaries, such as those on the Ethics, Physics, De anima, and early parts of the Metaphysics; but it comes to grips with profound problems of Aristotelian philosophy inherent in the conflicting views of Greek and Arab commentators. I. T. Eschmann rightly noted that “it represents the high water-mark of St. Thomas's expository skill. ” 1 In long, subtle digressions, Thomas discusses and evaluates the views of other commentators reported by Simplicius, as well as the views of Simplicius himself, who is a primary source in this commentary. As in earlier commentaries, Thomas was also concerned with the teaching of Averroes, which deeply influenced the masters in arts at Paris in the late 1260s and throughout the 1270s. The excessive adoption of Averroes by masters in arts resulted in the condemnation of thirteen Averroist theses on December 10, 1270, by the bishop of Paris, Etienne Tempier, and in the more sweeping condemnation by the same bishop on March 7, 1277. Simplicius and Averroes are in fact the two basic sources for Thomas's commentary on De caelo.
Thomas did not comment on De caelo until he had the full text in hand, together with the commentary of Simplicius. Although there were a number of translations of Aristotle's De caelo available from the Arabic, Thomas insisted on having a good translation from the Greek corrected by his friend and confrère William of Moerbeke. Wherever translations existed from the Greek, Moerbeke did not translate anew but rather revised specific readings of words and phrases according to a Greek exemplar. The first translation of De caelo from the Greek was made by Robert Grosseteste, the bishop of Lincoln, between 1247 and 1253, the date of his death. Grosseteste's translation went only as far as Book III, c. 1, 299a11; but he also translated the corre-