 Alexander was a Peripatetic philosopher and commentator, active in the late second and early third century CE. He continued the tradition of writing close commentaries on Aristotle’s work established in the first century BCE by Andronicus of Rhodes, the editor of Aristotle’s ‘esoteric’ writings, which were designed for use in his school only. This tradition reflected a gradual revival of interest in Aristotle’s philosophy, beginning in the late second century BCE, and helped to reestablish Aristotle as an active presence in philosophical debates in later antiquity. Aristotle’s philosophy had fallen into neglect and disarray in the second generation after his death and remained in the shadow of the Stoics, Epicureans, and Academic skeptics throughout the Hellenistic age. Andronicus’ edition of what was to become the Corpus Aristotelicum consolidated a renewed interest in Aristotle’s philosophy, albeit in a different form: active research was replaced by learned elucidations of The Philosopher’s difficult texts. The commentaries themselves served as material for the exposition of Aristotle’s work to a restricted circle of advanced students. Hence each generation of teachers produced their own commentaries, often relying heavily on their predecessors’ work. Thus, the ‘scholastic’ treatment of authoritative texts that was to become characteristic of the Middle Ages had already started in the first century BCE. Alexander, due to his meticulous and philosophically astute exegesis of a wide range of Aristotle’s texts, in logic, physics, psychology, metaphysics and ethical topics, became known as the exemplary commentator throughout later antiquity and the Arabic tradition. He is often referred to simply as ‘The Commentator’ (ho exêgetês), later sharing this title with Avicenna or Averroes. Because there is little evidence on Alexander’s life and activities, his commentaries and his short treatises on topics related more or less closely to Aristotelian doctrine provide all the information we have about him as a philosopher and a man. As these writings show, his main contemporary opponents were the Stoics, but there is also some evidence of a controversy with Galen. Alexander is not only regarded as the best of the ancient commentators but also as the last strictly Aristotelian one, whose aim was to present and defend Aristotle’s philosophy as a coherent whole, well suited to engage contemporary philosophical discussions. The later commentators were members of the Neoplatonist schools and were concerned to document the substantial agreement of Platonic and Aristotelian thought, and to integrate Aristotle’s work into their Neoplatonist philosophical system. But they continued not only to consult, discuss, but also to criticize, Alexander’s work, a fact that probably accounts for its survival.