Consistent with much of traditional, orthodox theology, Tolkien’s fictional theology labors to provide a dialectical balance and simultaneity of divine transcendence and immanence. We see this, for example, in his image of the Flame Imperishable which is presented as not only hidden “with Ilúvatar” (and hence undiscoverable by Melkor), but also as “sent forth” into the Void to burn “at the heart of the World.” As Tolkien writes in his commentary on the Athrabeth, the Flame Imperishable “refers rather to the mystery of ‘authorship’, by which the author, while remaining ‘outside’ and independent of his work, also ‘indwells’ in it, on its derivative plane, below that of his own being, as the source and guarantee of its being” (MR 345). Tolkien even went so far as to coin an Elvish expression for the principle of divine concurrence–described, for example, by St. Thomas as God causing the being in things “not only when they first begin to be, but as long as they are preserved in being”–calling it the “Oienkarmë Eruo,” “[t]he One’s perpetual production” and “management of the Drama” (MR 329). As twentieth-century Thomist Herbert McCabe explains this point in imagery notably similar to the Ainulindalë’s: “This God cannot be a Top Person summoned to fill the gaps in the natural order; this God must be at the heart of every being, acting in every action (whether determined or free), continually sustaining her creation over against nothing as a singer sustains her song over against silence—and that too is only a feeble metaphor, for even silence presupposes being.” 
If God is in all things, in another sense this is because all things are rather in God, a point which. One of the ways this has been traditionally expressed is in the Platonic notion of “participation,” an idea for which Tolkien too seems to have had some affinity. Thus, for Aquinas, God is “essential being” whereas everything else has merely “participated being,” a distinction that is further related to Thomas’s famous doctrine of analogy: because God and creatures exist in these fundamentally divergent manners, we can only ever predicate being of God and creatures in an analogous fashion (ST 1.13.5). It is the same idea of creation participating in the Creator, not only for their form, but for their existence itself, that Tolkien represents in his creation-myth. In the earlier, Book of Lost Tales version of the Ainulindalë, for example, Eru informs the Ainur that, in creating the world first sung by the Ainur in their Music and then seen by them in the Vision, he has in fact “caused [the world] to be—not in the musics that ye make in the heavenly regions, as a joy to me and a play unto yourselves, alone, but rather to have shape and reality even as have ye Ainur, whom I have made to share in the reality of Ilúvatar myself” (BLT 54-5, emphasis added). In creating things, Ilúvatar causes them to have a “share” or participation in his own reality, yet this does not mean that creation has the same, univocal kind of reality as Ilúvatar. It does mean, however, that its reality, by virtue of its participation in Ilúvatar, is analogous to his. As Tolkien differentiates these matters in one letter, the reality enjoyed by creation is a “secondary reality, subordinate to his [God’s] own, which we call primary reality…” (L 259).
 McCabe, God Matters, 59-60.
 On the notion of participation in St. Thomas’s thought, see Velde, Participation and Substantiality in Thomas Aquinas.
 For a recent discussion of and introduction to Thomas’s doctrine of the analogy of being and its historical interpretation and criticisms, see Miner, Truth in the Making, 11-18.