 Like the other commentaries in the ancient tradition, Alexander’s derive from his courses of lectures (‘readings’) on Aristotle’s works. In commenting, Alexander usually refrains from giving comprehensive surveys. He generally starts with a preface on the work’s title, its scope and the nature of the subject matter. He then takes up individual passages in rough succession by citing a line or two (this provides the ‘lemma’ for the ensuing discussion) and explaining what he considers as problematic (in explanatory paraphrases, clarifications of expressions, or refutations of the views of others), often in view of what Aristotle says about the issue elsewhere. This procedure clearly presupposes that the students had their own texts at hand and were sufficiently familiar with Aristotle’s philosophy as a whole. Alexander does not generally go through the text line by line, but chooses to discuss certain issues while omitting others. Paraphrases are interrupted by clarifications of terminology, and sometimes, at crucial points, by notes on divergent readings in different manuscripts and a justification of his own preference concerning Aristotle’s original words. Decisions on such philological problems are based on what makes better sense in conforming with Aristotle’s intentions here or elsewhere. As Alexander indicates, such philological explorations were considered as part of the commentator’s work (cf. On Aristotle Metaphysics A, 59, 1–9): “The first reading, however, is better; this makes it clear that the Forms are causes of the essence for the other things, and the One for the Forms. Aspasius relates that the former is the more ancient reading, but that it was later changed by Eudorus and Euharmostus.” Alexander’s concern with textual problems makes him a valuable source for textual criticism, as can be seen from Kotwick’s (2016) monograph on the text of Aristotle’s Metaphysics.