Aristotle's school treatises were given renewed prominence by Andronicus of Rhodes in the first century bc, and from then on numerous commentaries were written on them. The main modern edition runs to 15,000 pages. They are not just commentaries, but represent the thought and classroom teaching on philosophy quite generally first of the Peripatetic (that is, Aristotelian) school, and then of the Neoplatonists between ad 200 and 600, with further activity from the ninth century in the Islamic world and from the eleventh in the Byzantine.
The commentary movement followed and is commonly thought to have been inspired by the work of Andronicus of Rhodes, who, perhaps around 60 bc, began a massive study of Aristotle's writings (see Aristotle). Of the extant commentaries, the earliest come from Peripatetics of the first half of the second century ad, Adrastus and Aspasius. The early commentaries culminate in the work of the greatest Peripatetic elaborator of Aristotle, Alexander of Aphrodisias (second to third century; see Peripatetics). But the later commentaries by Themistius (fourth century), though presented as mere paraphrases, and though informed by certain Neoplatonist developments, are similar in content to those of Alexander.
Outside the Peripatetic school, the chief interest in the first century bc and the first two centuries ad focused on Aristotle's Categories (see Categories §1; Aristotle §7). Under the influence of the Neoplatonist Porphyry (third century), who rejected the complaint of his teacher Plotinus Aristotle's Categories ignores the Platonic Forms, Aristotle's logic and a wide selection of his other texts became a standard prerequisite for studying Plato in the Neoplatonist schools, Neoplatonism being by then the dominant philosophy (see Neoplatonism).
Porphyry's insistence on the harmony of Plato and Aristotle inaugurated a Neoplatonist tradition. His pupil Iamblichus (third to fourth century) and Iamblichus' pupil Dexippus further defended the compatibility of Aristotle's Categories with Plato's theory of Forms, and Iamblichus is even said to have denied that Aristotle contradicted the theory of Forms at all. In fifth-century Alexandria, first Hierocles and then Ammonius, son of Hermeas represented Plato and Aristotle as agreeing that god was the artificer of a beginningless universe. This harmonization, though historically untenable, proved philosophically fruitful, producing a new amalgamation of the ideas of Plato and Aristotle.
After Iamblichus, the study of Aristotle as a propaedeutic to Plato acquired a new significance, because the study of Plato himself was seen as leading to the Neoplatonist ideal of ascent to god. In Iamblichus' Platonic curriculum, Plato's Timaeus and Parmenides were put last, and seen as theological treatises describing the supreme divinities. From Ammonius onwards formalized introductions were prefixed to commentaries on Aristotle's Categories, the first Aristotelian work in the curriculum. The introductions covered ten points which, we are told, had been made standard by Ammonius' teacher Proclus (fifth century), one of them being that the eventual aim of studying Aristotle is ascent to god through the theological works of Plato. Even before the Categories, the curriculum included Porphyry's introduction to the Categories, known as the Isagog or Quinque Voces. Commentaries on that work were prefaced by a description of the nature of philosophy.
The commentaries of the Alexandrian Neoplatonist school after Ammonius are sometimes divided into portions which would have taken an hour to deliver as lectures. Often there is a double discussion, a protheoria or treatment of Aristotle's doctrine in a passage, followed by an exegesis of the exact wording of the text (exgsis ts lexeos).
In Alexandria, the Christian Platonist Philoponus (490-570s) worked out a complete alternative to the Aristotelian physics which the Neoplatonists had accepted, and thus went on to influence the development of Islamic and Western physics. Many of his unorthodox ideas were included in his attack Against Proclus, published in 529, but he also began to introduce them into his commentaries on Aristotle. Meanwhile Simplicius, a pious devotee of Neoplatonist religion, had left Athens for Persia as one of the seven displaced Athenian philosophers after the Christian emperor Justinian closed the Athenian Neoplatonist school in 529. He wrote bitterly about Philoponus' Christianity and about the unorthodox interpolations in his commentaries. He emphasizes the harmony of virtually all Greek thought, partly in order to rebut Christian charges of contradictions. It has been suggested that Simplicius finished up in Harrn, just within the borders of modern Turkey, and wrote his Aristotelian commentaries there after 532. It was from Harrn that Thbit ibn Qurra later went, to found the Platonizing school in Baghdad. This school became the driving force behind the translation into Arabic of Aristotle and his commentators in the ninth century, which was to inspire new philosophizing in the Islamic world.
Meanwhile commentaries were made available in Latin by Boethius (died c.525), but only on two logical works of Aristotle and on Porphyry's introduction (Isagog) to that logic. The Alexandrian School may have survived until the Arab capture of the city in 642, and a tradition continued in Constantinople. There in the twelfth century the princess Anna Comnena organized a circle that included the commentators Eustratius and Michael of Ephesus, whose commentaries were completed in 1138 or later. It may have been from Michael's workshops that James of Venice was able, around 1130, to collect Greek commentaries for translation into Latin. In the same century, Gerard of Cremona was translating Aristotelian commentaries into Latin from the Arabic versions. During the next century, the process of transmission from both languages to the Latin-speaking world turned from a trickle into a flood, and Thomas Aquinas was a beneficiary of this development. He was thus responding not just to Aristotle, but to Aristotle transformed by the ancient commentators.
The commentaries embed fragments from all 1,150 years of ancient philosophy from 550 bc to ad 600, notably those of the Presocratics. And many ideas which were previously thought to date from later times can actually be traced back to the commentators. In dynamics, the idea of an impetus, which in its medieval context has been hailed as a scientific revolution, can be seen to have travelled by an Arabic route from the sixth-century commentator Philoponus. Galileo in his early works mentions Philoponus more often than he mentions Plato. And Brentano in the nineteenth century got from the commentary tradition, and not from Aristotle himself, his idea that all activity of the mind is directed towards intentional objects.
See also: Aristotelianism in Islamic philosophy; Aristotelianism, medieval; Damascius; Neoplatonism in Islamic philosophy; Translators; Greek philosophy: impact on islamic philosophyRICHARD SORABJI