Notable points in this definition:A philosophical system developed at Alexandria in the 3rd Century A.D. based on a modified form of Platonism combined with elements of Oriental mysticism and some Judaic and Christian concepts and positing a single source from which all existence emanates and with which one can be mystically unified.
A “philosophical system” not a “religious belief”.
It combines Platonism, “oriental mysticism” (which there are numerous schools), and Judeo-Christian concepts.
This to me represents the first recognized attempt at Comparative Religion/Mythology.
And of course it would begin in Alexandria, the central “data warehouse” of ancient knowledge.
Joseph Campbell briefly mentions Neo-Platonism in Mythos II but since I don’t own a copy I can’t quote it verbatim. He mentions that the birth of Neo-Platonism was somewhere between 300 and 200 B.C. as Buddhist missionaries were being sent to establish colonies in Egypt. I’m suspicious that they also had some influence on Jewish culture as demonstrated by the Essenes.
There are also theories that state that Jesus was an Essen. This would explain the apparent “link” between early Christianity and Buddhist concepts.The Essenes were a Jewish religious group that flourished from the 2nd century BCE to the 1st century CE that some scholars claim seceded from the Zadokite priests[1]. Being much fewer in number than the Pharisees and the Sadducees (the other two major sects at the time) the Essenes lived in various cities but congregated in communal life dedicated to asceticism, voluntary poverty, and abstinence from worldly pleasures, including marriage and daily baptisms. Many separate but related religious groups of that era shared similar mystic, eschatological, messianic, and ascetic beliefs. These groups are collectively referred to by various scholars as the "Essenes." Josephus records that Essenes existed in large numbers, and thousands lived throughout Judæa. The Essenes believed they were the last generation of the last generations and anticipated Teacher of Righteousness, Aaronic High Priest, and High Guard Messiah, similar to the Prophet, Priest and King expectations of the Pharisees.
“a single source from which all existence emanates and with which one can be mystically unified.” This concept is also expressed as “I and the Father are One” or “Thou art That”.
However, unifying the two isn’t as “mystical” as it is methodical . As we see from ancient mythology, all be have to do is to undertake a “Hero’s Journey”.