 Ammonius (ca. 435/445–517/526) taught philosophy at Alexandria, where his father Hermeias had taught earlier. Known primarily for his commentaries on Aristotle, which were said to be of greater benefit than anyone else’s, he was also distinguished in geometry and astronomy. Himself a pupil of Proclus at Athens, at Alexandria Ammonius taught most of the important Platonists of the late 5th and early 6th centuries: Asclepius, Damascius and Simplicius, Eutocius, and Olympiodorus; Elias and David are considered indirect pupils of his. Damascius, who went on to head the school at Athens, heard Ammonius lecture, but attached himself rather to the mentorship of Isidore and followed him to Athens. While almost all of Ammonius’ Aristotle commentaries were published by students from his lectures, the large commentary on De Interpretatione was written up by Ammonius himself for publication. These commentaries are largely dependent on the lectures of Proclus and, to a lesser extent, Syrianus and thus indebted to their style of Iamblichean Neoplatonism. Ammonius is known for several contributions, especially for the introduction of an Alexandrian tradition of commentary on Aristotle, but also for the first preserved version of the set of questions to be answered preliminary to the study of Aristotle, the thesis that for Aristotle God is the efficient as well as final cause of the world, and the treatment of the sea battle of De Interpretatione 9 as one of three determinist arguments, along with the ‘Reaper’ and the argument from divine foreknowledge.