Here I would like to discuss whether or not J. R. R. Tolkien's account of Creation in the first chapter of his Silmarilion is compatible with St. Thomas' in ST I, q. 65, aa. 3-4. This will help to elucidate certain principles about the work of God and creatures in the making of things.
First, we can establish the conclusions of St. Thomas in these articles.
1. Respondeo “All bodies were created immediately by God [ex nihilo].”
2. No creature can create anything from nothing; angels did not create anything in the strict sense.
3. Respondeo: Matter obeys God’s bidding as its only proper cause.
4. “The corporeal forms that bodies had when first produced came immediately from God.”
5. “Even corporeal forms are derived from spiritual substances, not as emanating from them, but by movement (as the term of their movement).”
6. R. Obj. 2. Therefore, if things have their forms from angels through movement, it is because the idea of the thing was first in God, then in angels, and finally implanted in corporeal things like a seed.
Second, we can see if these conclusions are respected at least implicitly in Tolkien’s text, Ainulindale.
(I assume the identity of Illuvatar with God and the Ainur with angels.)
In regard to the first conclusion, “All bodies were created immediately by God [ex nihilo].” :
Illuvatar said, “EA! Let these things be! And I will send into the void the Flame Imperishable, and it shall be at the heart of the World and the World shall Be.” (p.9)
The second conclusion, that no creature can create anything from nothing; angels did not create anything, is respected because only Illuvatar made the world be, and “He made first the Ainur, the Holy Ones, that were the offspring of his thought” that is, the angels. (p.1)
The third and fourth conclusions:
Matter alone obeys God’s bidding as its proper cause.
“The corporeal forms that bodies had when first produced came immediately from God.”
Illuvatar said to the Ainur, “I know the desire of your minds that what ye have seen may verily be, not only in your thought, but even as ye yourselves are, but other. Therefore I say EA! Let these things be!” (p.9)
Comments: The Ainur were powerless to cause their thoughts to have real, as opposed to merely mental, existence; only Illuvatar could order formalized matter to come into being. These new things came immediately from Him as their primary efficient cause. They also came from Him directly as their formal cause, because the Ainur affected the forms only by “adorning” the theme already set for them by Illuvatar (cf. next section).
The fifth conclusion, “Even corporeal forms are derived from spiritual substances, not as emanating from them, but by movement (as the term of their movement).”:
“Of the theme that I have declared to you, I will now that ye make in harmony together a Great Music…ye shall show forth your powers in adorning this theme, each with his own thoughts and devices, if he will.” (p.1)
Comments: The forms of things are a product of the movement of the Ainur’s thoughts and will, an exercise of their power, not emanations of their substance.
The sixth conclusion, "if things have their forms from angels through movement, it is because the idea of the thing was first in God, then in angels, and finally implanted in corporeal things like a seed.":
“And [Illuvatar] spoke to them, propounding to them themes of music; and they sang before him.” (p.1) Illuvatar said to the Ainur, “Behold your music! This is your minstrelsy; and each of you shall find contained herein, amid the design that I set before you, all those things which it may seem that he himself devised or added.” (p.6)
Comments: The content of the Ainur’s song is their development of Illuvatar’s theme: their originality is only secondary and subordinate. Complete originality, apart from the theme of Illuvatar, is portrayed as corruption: “It came into the heart of Melkor to interweave matters of his own imagining that were not in accord with the theme of Illuvatar…some of these thoughts he now wove into his music, and straight-way discord arose about him.” (p.4) This implies that apart from Illuvatar’s theme there is no harmony, because He is the source of harmony. Thus, the forms of things were passed from Illuvatar to the Ainur and finally into reality; at each stage, Illuvatar was the primary mover.
In sum: yes, Tolkein's account of creation in the Silmarilion, at lest the part we discussed here, seems compatible with Thomas' account in ST I, q. 65, aa. 3-4