'It's a Gift!'
That so many people, both Christian and non-Christian, find Tolkien's subcreation to be so true-to-life is evidence that the Christian worldview from which he writes does point to the Truth beneath it all. When incarnational spirituality and sacramental spirituality are joined, it doesn't take "fantasy" to see the divine working in everyday life and everyday people. That awareness makes allegory unnecessary and, indeed, limiting. Allegory, after all, is constructed by the finite mind of the author. Story, on the other hand, if used rightly, isn't allegory but sacrament. Its elements don't stand for something else, as they do in allegory; the Story has its own reality. But that reality points to the deeper Truth that acts as its foundation, and which neither we nor the author will ever completely comprehend.
Tolkien's use of the term "secondary creation" implies that there is a primary creation with a reality of an entirely different kind and of an infinitely higher order. The term "subcreation" implies the same thing; a subcreation by definition is at a lower level than the Creation it's subordinate to. The purpose of a true subcreation (as opposed to simply an internally consistent setting for a fantasy story) is to provide a glimpse of primary reality from a perspective we might otherwise not see. In Tolkien's closest-to-autobiographical story, "Leaf by Niggle," Niggle spends his entire life trying to paint a perfect tree. But for this attempt at subcreation, he doesn't take one tree as a model and copy it cell by cell or follow every minute branching. He was painting the tree that was present in his imagination, the place a subcreation needs to come into existence before the artist can share it with the world. His imagined tree drew from everything he knew and understood and felt about trees. Tolkien drew on everything he knew and understood and felt about Words and Story as he created Middle-earth, and his faith and personal history supplied the roots.
If Tolkien had created nothing but the "facts" about Middle-earth, it would still be an incredible accomplishment. The amazing internal consistency and the sheer size of the project are breathtaking in themselves.
But the "facts" are only the surface. What draws so many of us to the Middle-earth of LotR, I believe, is the Truth we sense behind the facts - the primary creation Tolkien gives us a glimpse into, as Niggle tried to paint a perfect tree in order to provide a glimpse of the forest and the mountains beyond. A lot of people have said they wish Middle-earth were real. But rather than wishing for primary reality for its facts - that is, for the things that are true only within the secondary creation - I think what most of those people are really wishing for is the Truth that it points to. We want to become immersed in the primary creation Tolkien was attempting to show us, but of which he could give us only a glimpse because he himself had seen only a tiny corner of it.
The primary reality Tolkien shows us a glimpse of in LotR is a creation in which God acts in everyday events and in and through everyday people, even when they are unaware of it. God's presence has been so absorbed into the fabric of creation, and especially into what it is that makes us human, that we don't always notice it, any more than readers of LotR as an adventure story always notice the religious elements absorbed into it (although they can be affected by them even if they don't notice them). It's a creation in which everything that exists gives glimpses not of "elf magic," but of the real supernatural power that is behind and beneath it, as the natural abilities of the Elves were given to them by Ilúvatar. It's a creation in which community is something tangible and has a real effect on events. There's no way to separate "secular" from "religious" or "mundane" from "holy," because it all exists in and through God - which makes it inescapable that God's presence will be "felt on every page," even if the characters themselves aren't aware of it. It's a reality in which, to borrow an image from Thomas Merton, people walk around shining like the sun because of the spark of divine life they carry.
That creation is something we don't need to wish for and Tolkien didn't need to invent, because it underlies every particle of existence and every moment of life. We just need to discover it.
Not that we can do this easily or quickly. Since it involves mystery, it's something we'll never finish; as my theology teacher said, "That's why heaven has to last forever."
...and that's why I'll never be finished reading The Lord of the Rings.