Thanks Andrew---I'd like to hear more from Antonio too.
I agree that Christian orthodoxy does not posit two eternal, opposing principles of good and evil, and that makes the "origin myth" of Satan key. Whether it "allows" this idea of real personified evil may be a different question, since I believe even the Vatican has a house exorcist.
Regardless, the Devil is largely a folk concept, like the Harrowing of Hell and so on, that was invented (or built up from pieces) during the Middle Ages. It might be more correct to say "orthodox tradition" rather than "orthodoxy"---Christianity has many contradictory traditions, as all religions do.
We also have two testaments of the Bibles to deal with. The Serpent in the Garden is in Genesis, which is most closely tied with myths of creation and precedes all other books. The name Satan does not appear there---but "everyone" agrees the serpent is Satan. Satan appears in the New Testament. Lucifer appears in the Old, but see below ...
I just found the following bit of illumination on a Mormon web site and make no guarantees about it, but it is an example of the kind of transformations that occur over centuries (
http://www.lds-mormon.com/lucifer.shtml):
"Lucifer makes his appearance in the fourteenth chapter of the Old Testament book of Isaiah, at the twelfth verse, and nowhere else: "How art thou fallen from heaven, O Lucifer, son of the morning! How art thou cut down to the ground, which didst weaken the nations!" . ..Lucifer is a Latin name.... In the original Hebrew text, the fourteenth chapter of Isaiah is not about a fallen angel, but about a fallen Babylonian king, who during his lifetime had persecuted the children of Israel. It contains no mention of Satan, either by name or reference <
http://www.ankenyiowa.gov/index.aspx?recordid=1481&page=22>. The Hebrew scholar could only speculate that some early Christian scribes, writing in the Latin tongue used by the Church, had decided for themselves that they wanted the story to be about a fallen angel, a creature not even mentioned in the original Hebrew text, and to whom they gave the name "Lucifer."
Why Lucifer? In Roman astronomy, Lucifer was the name given to the morning star (...Venus). The morning star appears in the heavens just before dawn, heralding the rising sun. The name derives from the Latin term lucem ferre, bringer, or bearer, of light." In the Hebrew text the expression used to describe the Babylonian king before his death is Helal, son of Shahar, which can best be translated as "Day star, son of the Dawn."
The scholars authorized by ... King James I to translate the Bible into current English did not use the original Hebrew texts, but used versions translated ... largely by St. Jerome in the fourth century. Jerome had mistranslated the Hebraic metaphor, "Day star, son of the Dawn," as "Lucifer," and over the centuries a metamorphosis took place. Lucifer the morning star became a disobedient angel, cast out of heaven to rule eternally in hell. Theologians, writers, and poets interwove the myth with the doctrine of the Fall, and in Christian tradition Lucifer is now the same as Satan, the Devil, and --- ironically --- the Prince of Darkness.
I wonder if Iubar, in the context of BOTNS, should somehow be read more in terms of "heralding the rising sun" (the New Sun?!) than "fallen angel." Or both.
Anyway, you can see why I emphasize Milton's Lucifer, since Paradise Lost is a retelling of Genesis and Lucifer the angel is nowhere else so much expounded upon.