Ammonius Saccas was a Greek philosopher who was active around 240AD. Ammonius Saccas taught Neoplatonism and spawned two renowned pupils: the Christian Origen and the Neoplatonist Plotinus. Plotinus, in turn, had a pupil who claims to have also known Origen. His name was Porphyry, and he claims that Ammonius was once Christian but converted away (he also exposes Origen’s Greek influences):

…I refer to Origen, who is highly honored by the teachers of these doctrines.

6. For this man, having been a hearer of Ammonius, who had attained the greatest proficiency in philosophy of any in our day, derived much benefit from his teacher in the knowledge of the sciences; but as to the correct choice of life, he pursued a course opposite to his.

7. For Ammonius, being a Christian, and brought up by Christian parents, when he gave himself to study and to philosophy straightway conformed to the life required by the laws [Platonism]. But Origen, having been educated as a Greek in Greek literature, went over to the barbarian recklessness [Christianity]…

8. For he was continually studying Plato, and he busied himself with the writings of Numenius and Cronius, Apollophanes, Longinus, Moderatus, and Nicomachus, and those famous among the Pythagoreans. And he used the books of Chæremon the Stoic, and of Cornutus. Becoming acquainted through them with the figurative interpretation of the Grecian mysteries, he applied it to the Jewish Scriptures.

Eusebius provides some commentary on these claims:

9. These things are said by Porphyry in the third book of his work against the Christians. He speaks truly of the industry and learning of the man, but plainly utters a falsehood (for what will not an opposer of Christians do?) when he says that he went over from the Greeks, and that Ammonius fell from a life of piety into heathen customs.

10. For the doctrine of Christ was taught to Origen by his parents, as we have shown above. And Ammonius held the divine philosophy unshaken and unadulterated to the end of his life. His works yet extant show this, as he is celebrated among many for the writings which he has left. For example, the work entitled The Harmony of Moses and Jesus, and such others as are in the possession of the learned.

So, Ammonius was a renowned Platonic philosopher that mentored Plotinus. Plotinus’ own pupil talks about Ammonius’ rejection of Christianity, but Eusebius who lived in Palestine (Ammonius taught in Alexandria) and writing decades(?) after Porphyry, claims that Porphyry was wrong. His evidence is existent books by Ammonius (now lost to time).

Eusebius also references to Ammonius elsewhere:

Ammonius the Alexandrian, having exerted a great deal of energy and effort as was necessary, bequeaths to us a harmonized account of the four gospels. Alongside the Gospel according to Matthew, he placed the corresponding sections of the other gospels.

Jerome (347-420) echoes Eusebius’ claims that Ammonius remained a Christian:

Ammonius, a talented man of great philosophical learning, was distinguished at Alexandria, at the same time. Among many and distinguished monuments of his genius, is the elaborate work which he composed On the harmony of Moses and Jesus, and the Gospel canons, which he worked out, and which Eusebius of Caesarea, afterwards followed. Porphyry falsely accused him of having become a heathen again, after being a Christian, but it is certain that he continued a Christian until the very end of his life.

The church fathers were eager to count Ammonius as one of their own. But looking at what we know of Ammonius, he seems more like a gnostic or Platonist. No one would dispute that Ammonius taught Neoplatonism. Plotinus said of Ammonius “Here is the man I have been looking for”, and then became his devoted disciple. Porphyry writes:

Plotinus himself remained a long time without writing, but he began to base his Conferences on what he had gathered from his studies under Ammonius.

Plotinus’ teachings (our best source of Neoplatonistic beliefs) are said to have been taught by Ammonius! Ammonius also had “secret teachings” that his disciples attempted to keep hidden (a practice mirroring Gnosticism or mystery cults):

Erennius, Origen [this is not the Christian Origen], and Plotinus had made a compact not to disclose any of the doctrines which Ammonius had revealed to them. Plotinus kept faith, and in all his intercourse with his associates divulged nothing of Ammonius’ system.

The Church Fathers were very eager to include this devoted Neoplatonist as one of their own. This is very telling of the intellectual culture of Christianity in the 3rd and 4th centuries. It also makes one wonder what was contained in Ammonius’ books (e.g. On the harmony of Moses and Jesus) if Ammonius actually did write these books.