Aristotle’s Categories was a fundamental text in the medieval Latin philosophical tradition. Supplemented with an introduction by the late-ancient Neoplatonist philosopher Porphyry, it served, from the eleventh century onward, as the first book of the medieval philosophical curriculum. As a result of its theoretical and educational primacy, it became the object of an extraordinarily vast commentary tradition that includes commentaries by some of the most well-known medieval philosophers: Peter Abelard in the twelfth century; Robert Kilwardby, Albert the Great, and John Duns Scotus in the thirteenth; and William of Ockham, Walter Burley, and John Buridan in the fourteenth.