  Byzantium in the 6th century witnessed at once a last flourishing and a dramatic decline of the tradition of composing philosophical commentaries on the works of Plato and Aristotle, a tradition which began in earnest in the 2nd century CE. David, together with the almost equally enigmatic Elias, and Stephanus, belong to the final stage of this tradition that reached its pinnacle in the 6th century’s first half with the great commentaries of Ammonius Hermeiou and his pupils Simplicius and John Philoponus in the East, and with Boethius in the West. If we discount a commentary on the Categories which the manuscript tradition uniformly attributes to ‘David’ but which, in style and doctrine, is more closely related to works attributed to ‘Elias’, there remain two texts we have to consider as his works, one entitled ‘Prolegomena philosophiae’ (‘Introduction to Philosophy’), the other lectures on Porphyry’s ‘Introduction to Aristotle’s Categories’. The author of these texts refers to Olympiodorus four times; he may have been his pupil. Olympiodorus, who was a pagan, held the chair of philosophy at Alexandria as a successor to Ammonius and Eutocius for well over 30 years, from around 530 to about 565. These are the only pieces of evidence that provide us with a rough estimate as to the time of composition.