 By the time Kilwardby wrote his commentary, however, a Latin translation of a commentary by Averroes on the Prior Analytics was becoming known in the West. Averroes wrote three kinds of commentaries on Aristotle’s works, called ‘minor’, ‘middle’, and ‘major’ or ‘great’ based on their length and detail. In the 1220s and 1230s, William of Luna translated Averroes’ middle commentary on Porphyry’s Isagoge as well as his middle commentaries on Aristotle’s Categories, On Interpretation, and Prior Analytics. In addition to these, a major commentary on the Posterior Analytics also became available. In the middle commentaries, Averroes does not go much beyond Aristotle, adhering closely to the letter of Aristotle’s text and deviating only on occasion. Nevertheless, his commentaries played an indispensable role throughout the later Middle Ages in the teaching and study of these difficult texts.