Ammonius Saccas (3rd century AD) was a Greek philosopher from Alexandria who was often referred to as the founder of the Neoplatonism. He had a humble background, and appears to have earned a living as a porter at the docks of Alexandria, hence his nickname of "Sack-bearer" (Sakkas for sakkophoros).

All that is known of the life and teachings of Ammonius is retained in a fragment of Porphyry writing quoted in the writings of Eusibeus and Jerome.

Eusebius, History of the Church, VI, 19:1-12: As an example of this absurdity take a man whom I met when I was young, and who was then greatly celebrated and still is, on account of the writings which he has left. I refer to Origen, who is highly honored by the teachers of these doctrines. 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. 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. But Origen, having been educated as a Greek in Greek literature, went over to the barbarian recklessness. And carrying over the learning which he had obtained, he hawked it about, in his life conducting himself as a Christian and contrary to the laws, but in his opinions of material things and of the Deity being like a Greek, and mingling Grecian teachings with foreign fables. 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 Chaeremon 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 then states:]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. 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.

Jerome, On Illustrious Men 55: Porphyry falsely accused him [Ammonius] 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 fragments left from Porphyry's writings, Against the Christians, give details about the life and teachings of Ammonius. According to Porphyry, his parents were Christian, but upon learning Greek philosophy, Ammonius rejected his parents' religion for polytheism. This conversion is denied by the Christian writers Jerome and Eusibeus, who stated that Ammonius remained a Christian throughout his lifetime. This disagreement accounts for why some believe there exist two different men: Ammonius Saccus, the Neoplatonist, and Ammonius of Alexandria, the Christian.

After a long period of study and meditation, Ammonius opened a school of philosophy in Alexandria, where his principal pupils were Herennius, Origen of Alexandria, Cassius Longinus, and Plotinus.

Due to the confusion surrounding Ammonius's religion, many scholars claim that he deliberately wrote nothing, and, with the aid of his pupils, kept his views secret after the manner of the Pythagoreans; thus, the scholars believe that his philosophy must be inferred mainly from the writings of Plotinus. However, Ammonius did write two books , which had a direct impact on Christian doctrine.

While Eduard Zeller points out there is reason to think that Ammonius's doctrines were closer to those of the earlier Platonists than to those of Plotinus , Hierocles, writing in the 5th century, states that Ammonius' fundamental doctrine was an eclecticism derived from a critical study of Plato and Aristotle. Another part of Ammonius's fundamental doctrine was based on the gospels. The two books that are attributed to him dealt with the gospels and were lauded by Eusebius and Jerome. One titled Harmony of the Gospels still exists in Latin ; the other has been either lost or plagiarized under another name.

His neoplatonic admirers credited him with having reconciled the quarrels of the two great schools of the philosophy of Plato and Aristotle. In Christian circles, according to Eusebius, he was "celebrated among many for the writings which he has left". Smith's Dictionary of Greek and Roman Biography and Mythology credits him with holding to a kind of "philosophical theology" in combining the study of philosophy with Christianity.

The death of Ammonius Saccus also known as Ammonius of Alexandria and Ammonius the Christian and Neoplatonist, is variously given as between AD 240 and AD 245 at a great age.

The Ammonius crater on the Moon was named in his honor.

References
http://www.ancientlibrary.com/smith-bio/0155.html

• The Reaction to the Bible in Paganism. http://www.bibleinterp.com/articles/Cook_Reaction_Bible_Paganism.htm
  
• Encyclopedia Americana 1961 ed. Plotinus Article
  
• Porphyry, Against the Christians (2004). Fragments. http://www.tertullian.org/fathers/porphyry_against_christians_02_fragments.htm
  
• http://www.iep.utm.edu/o/origen.htm