One important mode of philosophical expression from the end of the Hellenistic period and into Late Antiquity was the philosophical commentary. During this time Plato and Aristotle were regarded as philosophical authorities and their works were subject to intense study. This entry offers a concise account of how the revival of interest in the philosophy of Aristotle that took place towards the end of the Hellenistic period eventually developed into a new literary production: the philosophical commentary. It also follows the commentary tradition into Late Antiquity in order to account for the vitality and richness of this tradition. The reader should keep in mind that the study of Aristotle in the form of the commentary did not mean the cessation of genuine philosophical thought. Quite the contrary: authors customarily used the commentary format not only to expound the works of Aristotle, but also as a vehicle for original philosophical theorizing. One consequence of this approach was that, at least at the beginning, the return to the works of Aristotle did not involve the..