According to Tolkien’s theology of sub-creation, then, human Fantasy is a divinely appointed and even privileged means for imaginatively exploring and so celebrating (paying “tribute”) to God’s own infinite “variety,” and in that way extending or “effoliating” God’s own purposes within creation. Not surprisingly, it is the same theology of sub-creative possibility, as rooted in God’s own act of creation, that Tolkien brings to bear on and gives poetic expression to in his literary writings.
In his poem “Mythopoeia,” for example, Tolkien characterizes the work of sub-creation in terms of a lens through which the “white light” of God’s creation becomes “splintered” into “many hues, and endlessly combined / in living shapes that move from mind to mind” (TL 101). The image of the sub-creator as God’s agent for refracting God’s own light of creation parallels Maritain’s account in Art and Scholasticism of how the artist’s concepts find in God “their sovereign analogue” and which therefore represent “dispersed and prismatized reflection[s] of the countenance of God.” Consistent with this sentiment, in the conclusion of his poem where he describes man’s future state of glory, Tolkien indicates that the light of creation from which the sub-creator takes his inspiration is itself only one ray within the infinite, uncreated light that is God’s own being:
In Paradise they look no more awry;
and though they make anew, they make no lie.
Be sure they still will make, not being dead,
and poets shall have flames upon their head,
and harps whereon their faultless fingers fall:
there each shall choose for ever from the All.
Sub-creative freedom involves, both now and forever, a choosing from the divine “All” in whom all possibility is contained.
And it is this same theology of sub-creation, finally, which Tolkien presupposes and in part dramatizes in his Ainulindalë through the Ainur’s sub-creation of their Music. On the one hand, while the Ainur are able and invited to sub-create beyond the original theme taught them by Ilúvatar, the sub-creative possibilities which they discover through their Music are in no way independent of Ilúvatar. Rather, as Tolkien describes the Ainur’s sub-created themes in one letter, they represent so many “interpretations of the mind of the One” (L 284). Their act of sub-creating, in other words, is an act of exegeting, as it were, the divine being. In their act of sub-creation, accordingly, the Ainur are best seen as imitating something of God’s own act, as Thomas puts it, of “inventing” or “devising” the divine ideas through the self-knowledge or interpretation that constitutes the divine Word and “art of God.” David Bentley Hart illustrates well the affinity here between Tolkien and St. Thomas in his account of the traditional view of divine possibility held by Thomas, yet using the same musical imagery employed by Tolkien:
The “theme” of creation is the gift of the whole, committed to limitless possibilities, open to immeasurable ranges of divergence and convergence, consonance and dissonance (which always allows for the possibility of discord), and unpredictable modulations that at once restore and restate that theme. The theme is present in all its modifications, for once it is given it is recuperated throughout, not as a return of the Same but as gratitude, as a new giving of the gift, as what is remembered and as what, consequently, is invented. The truth of the theme is found in its unfolding, forever. God’s glory is an infinite “thematism” whose beauty and variety can never be exhausted, and as the richness of creation traverses the distance of God’s infinite music, the theme is always being given back. Because God imparts the theme, it is not simply unitary and epic but obeys a Trinitarian logic: it yields to a contrapuntal multiplicity allowing for the unfolding of endlessly many differing phrases, new accords, “explicating” the “complication” of divine music.
Ilúvatar himself hints at this respect in which the Ainur’s sub-creative discoveries, for all their freedom and lack of coercion, are nevertheless already anticipated within and pre-contained by the divine mind, when he tells them how in the Vision of the history of the world corresponding to the Ainur’s Music, each of them will behold “all those things which it may seem that he himself devised or added” (S 17, emphasis added). In the earlier version of the Ainulindalë from The Book of Lost Tales, Ilúvatar is slightly less subtle about the source of the Ainur’s sub-creative possibility when he gives them the command to develop the original theme he has taught them: “I have not filled all the empty spaces, neither have I recounted to you all the adornments and things of loveliness and delicacy whereof my mind is full. It is my desire now that ye make a great and glorious music and a singing of this theme…” (BLT 53, emphasis added). As Michaël Devaux has observed—and quoting from Aquinas’s discussion of Augustine’s notion of angelic “morning knowledge,” or their “knowledge of the primordial being of things… according as things are in the Word” (ST 1.58.6)—“[t]o perceive the Word, before the creation, is precisely the situation which the Music has made possible for the Ainur.” Yet in The Silmarillion edition Ilúvatar makes matters plain enough when he explains to Melkor how, despite the latter’s efforts to achieve true novelty through his musical innovations, or rather deviations, in the Vision he will come to learn that all sub-creative possibility finds its home in Ilúvatar: “And thou, Melkor, shalt see that no theme may be played that hath not its uttermost source in me, nor can any alter the music in my despite. For he that attempteth this shall prove but mine instrument in the devising of things more wonderful, which he himself hath not imagined” (S 17). In his effort to go beyond the boundaries established by the beautiful rhythms of Ilúvatar’s original theme, Melkor succeeds not, as is his intent, in discovering or creating hitherto unrealized musical possibilities, so much as he does in nihilistically negating or distorting those possibilities provided for by the infinite perfection of Ilúvatar’s own being. What Melkor produces, in other words, is not music but anti-music, not an “interpretation” of Ilúvatar’s original theme, but an “alteration” of it (L 284). Yet even here, because his musical distortions are parasitic upon those rhythms and melodies which derive their possibility from the divine “mind” or “variety” of Ilúvatar, it follows that the ultimate meaning even of Melkor’s distortions are likewise beyond his control, but fall under the sovereignty of Ilúvatar. To the extent, in other words, in which evil is “real” and therefore possible, its own significance is determined by the one who is the God of the possible.
 Maritain, Art and Scholasticism, 30.
 Hart, The Beauty of the Infinite: The Aesthetics of Christian Truth, 282.
 “[I]ta cognitio ipsius primordialis esse rerum, dicitur cognitio matutina: et haec est secundum quod res sunt in Verbo.”
 Devaux, “The Origins of the Ainulindalë,” 102-3. On Augustine’s doctrine of angelic morning and evening knowledge as it applies to the Ainulindalë, see Houghton, “Augustine in the Cottage of Lost Play: The Ainulindalë as Asterisk Cosmogony.”
 As David Harvey observes, “[t]he [Ainur] are always second to Ilúvatar. The foundation of all that they do is within His design. Any incursion by Evil powers, any attempts to change the theme or the design, are taken and skillfully worked into the Theme so that the conclusion is exactly as it was intended.” Harvey, The Song of Middle-earth: JR.R. Tolkien’s Themes, Symbols and Myths, 32.