Of humble origin, he appears to have earned a livelihood as a porter; hence his nickname of "Sack-bearer" (Sakkas, for sakkoforos). The details of his life are unknown. After long study and meditation, Ammonius opened a school of philosophy in Alexandria. His principal pupils were Herennius, the two Origens, Cassius Longinus and Plotinus. As he designedly wrote nothing, and, with the aid of his pupils, kept his views secret, after the manner of the Pythagoreans, his philosophy must be inferred mainly from the writings of Plotinus. As Zeller points out, however, there is reason to think that his doctrines were closer to those of the earlier Platonists than to those of Plotinus. Hierocles, writing in the 5th century AD, states that his fundamental doctrine was an eclecticism, derived from a critical study of Plato and Aristotle. His admirers credited him with having reconciled the quarrels of the two great schools. His death is variously given between AD 240 and 245.
The details of the life of the philosopher Ammonius Saccas are so unclear that he has frequently been confused with a Christian philosopher of the same name. Eusebius (Church History, vi. 19), who is followed by Jerome, asserts that he was born a Christian, remained faithful to Christianity throughout his life, and even produced two works called The Harmony of Moses and Jesus and the Diatessaron, or Harmony of the Four Gospels. Porphyry, quoted by Eusebius (vi. 19. 6), however, says that he apostatized in later life and left no writings behind him. There seems no reason, therefore, to doubt that Eusebius is here referring to the Christian philosopher.