This is the first English translation of Proclus' commentary on Plato's Parmenides. Glenn Morrow's death occurred while he was less than halfway through the translation, which was completed by John Dillon. A major work of the great Neoplatonist philosopher, the commentary is an intellectual tour de force that greatly influenced later medieval and Renaissance thought. As the notes and introductory summaries explain, it comprises a full account of Proclus' own metaphysical system, disguised, as is so much Neoplatonic philosophy, in the form of a commentary.