  At the beginning of the sixth century, we find several late Neoplatonic philosophers who continue the ancient tradition of commentary writing. They include Boethius, Philoponus, Elias, David, pseudo-Elias, Stephanus, and Simplicius. Two of these in particular deserve mention. Simplicius (490–560) is important because his Commentary was translated into Latin by William of Moerbeke in 1266 and was subsequently read by Aquinas, Duns Scotus, and Ockham, among others, though apparently not by Albertus Magnus. In addition, Simplicius attempted to prove that there are ten and only ten categories, something that became the subject of dispute in the later Middle Ages.