The translation of Avicenna's "commentary" on Aristotle's Categories, Al-Maqulat (Part One, Volume Two of As-Shifa'), is given here with explanatory notes. Avicenna does not paraphrase the text. Rather, as he states, he comments upon what the correct doctrines are. He offers original doctrines on such topics as paronymy, the ontological square in Categories 2, predication, the antepredicamental rule, the number of the categories, distinction of primary and first substance, an account of relation, as opposed to relationship, the ontology of mathematical objects, and the predication of contraries. Avicenna uses and refers to these doctrines in his scientific works, particularly in his metaphysics.