I was wishing I could discover that Tolkien's Metaphysical Philosophy was unintentionally Stoic like I have for Star Wars and Final Fantasy VII and maybe even Zelda. But no, both Tolkien and C.S. Lewis are firm examples of Platonist Christianity.
It starts right with what the name Eru is said to mean in the opening lines of the Ainulindale and Valaquenta and the Index of the Silmarilion, "The One" and "He that is Alone". That comes from the Pythagorean concept of The Monad which became core to the Monotheism of Neopythagoreanism, Middle Platonism and Neoplatonism. Lewis does the same thing in the Space Trilogy by calling the first person of the Trinity the "Old One". The New Testament never uses any form of Mono to define God, the verses people often cite as saying "God is One" or "The Lord is One" have a different word being translated One which I argue is a misleading Translation, Unity or United is the idea being conveyed by that word.
Another part is the very concept of having the Valar do much of the heavy lifting in actually physically creating Arda, this echoes the Demiurge concept of Numenius of Apamea or Plutarch's Daimon subcreators and is firmly Unbiblical.
The most truly in-depth discussion of Theology in anything Tolkien wrote for his Middle Earth mythology is the Athrabeth Finrod Ah Andreth or The Debate of Finrod and Andreth, published in The History of Middle-Earth Volume X: Morgoth's Ring. It's in the style of a Platonic Dialogue but more importantly then that are three key things it reveals about Eru Iluvatar and Arda and Men.
In my copy of Morgoth's Ring (a Hardcover edition with a Red Sleeve) on page 311 near the bottom Finrod says that Arda "was made by Eru, but He is not in it" and goes on to basically say the same of Ea the equivalent term for the Universe/Cosmos. This God being outside the Universe concept is another idea that has been taken as a given by most Christian Theologians because of the influence of Platonism, but that I have come to view as actually contrary to Scripture, Stephen says in Acts 7 quoting Isaiah 66 that the Heavens are His Throne and The Earth his Footstool, and remember in Hebrew and Greek the Heavens means the Sky and Outer Space. making it fundamentally part of the Universe. The Ancient Platonists referred to the World of Forms where their transcendent God lived not as Heaven but as "A Place Beyond Heaven". The Biblical God is Imminent within the Universe not outside of it.
Next on page 314 Finrod explains that the Spirit/Souls of Men unlike those of Elves are not confined to Arda nor is Arda their Home. Thinking things like this about the nature of the Human Soul is a gateway drug to de-physicalizing the Resurrection, now Tolkien doesn't do that, Finrod's ultimate conclusion regarding the destiny of Men and the remaking of Arda involves their Bodies becoming as immortal as their Souls. But still I tend to be uncomfortable with even introducing a concept of the Soul being somehow less tied to The World then The Body is. But when interpreting The Bible this idea naturally comes from the previous one since Adam became a Living Soul when God Breathed the Breath of Life into him.
Then on page 318 they basically adapt the Platonic World of Forms concept to be in the Mind of Eru. Related to that is how the openings of both the Ainulindale and Valaquenta state that Eru made the Ainu of his thoughts. That comes from the 2nd Century Middle Platonsit Alcinous who defined the lesser god subcreators as Ideas made of the thoughts of the First God.
Now when I discussed Gnostic Interpretations of certain Anime and Video Games I mentioned how a lot of ideas we associate with Gnosticism are irrelevant to the point. Not all Gnostics believe the Demiurge and/or Old Testament God was Evil, nor was making good guys out of certain Biblical villains a requirement. The core is that Gnosticism believes The Physical World is in some way tainted by Evil, but the degrees can very.
The World Soul is a metaphysical concept I've mentioned on this Blog before mostly in relation to Stoicism, but versions of it existed in various forms of Platonism and Gnosticism as well. Tolkien's Cosmology winds up kind of incorporating two conflicting World Soul ideas.
The one thing in Tolkien's Middle Earth Theology that seems close to my Christian Stoicism is the Flame Imperishable, which Tolkien in one letter identified with The Holy Spirit, it's also placed in the Center of the World and is the source of all Sapient Life. So easily comparable to the Stoic concept of the World Soul and Pneuma, if it weren't in the context of all this Platonism I'd be much more excited about it.
However the Middle Platonist Plutarch introduced the idea of an Evil World Soul, a World Soul that is responsible for corrupting all physical matter, which Numenius of Apamea also agreed with. And this leads us to the entirety of what Morgoth's Ring is about, Morgoth emptied his essence into all of Arda corrupting and marring it, this taint is called the Morgoth Element.
Now The New Testament does agree that the current world is imperfect, it is still far from God's final design for it. But the blame for that is chiefly Man's Sin not something an evil god did, however mainstream Christianity loves to overstate the significance of Satan.
None of this changes my enjoyment of Middle Earth set Fiction, in fact I'm glad to have a popular Fantasy Universe that is rather Gnostic to contrast with the ones I feel get called Gnostic unfairly.
And it's hard to tell how much any of this actually reflects Tolkien's real Religious beliefs. On the one hand he seems to have clearly said to his Priest friend not to take it that seriously. But on the other every core idea I've objected to here has been genuinely believed by many Christian Theologians.
