After introducing Porphyry’s commentary, this chapter asks how Porphyry saw himself at the time of writing. Was it as a ‘Neoplatonist’ and pupil of Plotinus as usually presumed? Does he write as a mathematician and scientist or as a philosopher? Assuming he sees harmonics as a natural interest of the philosopher, what sort of philosopher does he represent himself as? He could claim to be embarking upon a ‘Pythagorean’ task rather than a ‘Platonist’ one, though the two were hard to distinguish in this era. Either would involve the Timaeus. His persona may have a bearing on the work’s date. The long discussion on logos and sensation is examined for indications of Porphyry’s sources and allegiance. This epistemology is distinctive, and the most distinctive features are independent of Plotinus. The section’s eclecticism and polymathy make it hard to associate with a single school, like Thrasyllus, Porphyry’s only named authority here. Porphyry’s persona is in fact complex, as much Pythagorean as Platonist, with an early dating feasible, allowing for debts to Longinus and to the mathematician Demetrius rather than to Plotinus. A Pythagorean’s interest in harmonics is natural.