According to St. Bonaventure, the personal property that distinguishes the Father from the Son and the Spirit is his “innascibility” (innascibilitas), the fact, that is, that unlike the Son, he is entirely unbegotten (Breviloquium 1.3). As Russell Friedman has pointed out in his Medieval Trinitarian Thought from Aquinas to Ockham, this position becomes somewhat characteristic of the Franciscans generally.
Anselm seems to see things a little differently. In his Monologion, chapter 39, he writes that “it is the distinguishing characteristic of the second [person of the godhead] that is born from the first, and it is the distinguishing characteristic of the first [person] that the second is born from him” (Williams trans.). For Anselm, in other words, what makes the Father to be the Father has less to do with what he and the son do not share in common (the Son being begotten, the Father unbegotten), than it does with–in perhaps proto-Dominican fashion–with the relation that the Father and Son do share in common. The Son is the Son because he is begotten by the Father, and the Father is the Father because he begets the Son.
Metaphysics of the Music, part 33
Tolkien’s measured agreement with Kant notwithstanding, it is exactly this initial stance of existential disinterest or indifference found in the Ainur’s Music that finds itself radically transcended in the surpassing beauty of the Vision. While it is through their Music that the Ainur gradually come into greater contact and communion with each other, it is only in the Vision that they are for the first time confronted with the startling awareness of the possibility of things “other than themselves, strange and free” (Silmarillion 18). This theme of otherness, touched on previously, is another central theme in Tolkien’s writings and one that has its roots in the metaphysical realism of St. Thomas, as Alison Milbank, for example, has pointed out. Nor are the Ainur by any means the only species in Tolkien’s mythical world to be defined in terms of this fundamental orientation towards things other. As I have argued previously, the theme of otherness is embodied at the very deepest and highest level of Tolkien’s fictional reality in the proto-Trinitarian theology of Middle-earth: the reason God creates things other than himself is because the Creator in a very real sense is already an other to himself. And as St. Thomas argues, because the Creator is a lover of otherness by his own nature, it follows that those who have been specially created after his image will be similarly marked by this heavenly desire for the existence of things other than oneself. This principle is perhaps brought home most dramatically in Tolkien’s fiction through the Valar Aulë, in whose desire to fashion the Dwarves (notwithstanding its folly and futility) there is an excellent expression of the aforementioned, Thomistic principle that creaturely likeness to divine goodness requires a “plurality and inequality” of creatures in which higher beings, in imitation of God, might communicate to others the goodness they have received from him. As Aulë repentantly explains to Ilúvatar his motive in trying to fashion the Dwarves,
I did not desire such lordship. I desired things other than I am, to love and to teach them, so that they too might perceive the beauty of Eä, which thou has caused to be. For it seemed to me that there is great room in Arda for many things that might rejoice in it, yet it is for the most part empty still, and dumb. And in my impatience I have fallen into folly. Yet the making of things is in my heart from my own making by thee; and the child of little understanding that makes a play of the deeds of his father may do so without thought of mockery, but because he is the son of his father. (S 43)
 “There is one further element in this metaphysics [of Chesterton and St. Thomas] that we need in order to understand Tolkien’s philosophy… [T]he element I would stress is the otherness or objectivity of things. Only through the reality of the world can the mind, according to Thomas, reach out to otherness and become the object. As Maritain writes, ‘it is in its totality reaching out towards the object, towards the other as other; it needs the dominating contact of the object, but only that it may be enriched by it… fertilized by being, rightly subjected to the real’. To sum up, Aquinas, according to Chesterton, teaches ‘the reality of things, the mutability of things, the diversity of things’… [T]his is a philosophy that can be found at every level of Tolkien’s fictional project… The world Tolkien invents is, of course, fictional, but it is famously realistic in its density and completeness of realization… To invent a world at all, as fantasy writers continue to do, is to commit to metaphysics… For the fantasy writer not only mimics the divine act of creation but he or she, by creating a self-consistent, independent world also witnesses to the existence of an Is: to Ens.” Milbank, Chesterton and Tolkien as Theologians: The Fantasy of the Real, 17-18.
Bonaventure’s Breviloquium, part 5
According to Bonaventure, why did God bring physical nature into existence over the course of six days? Because of the Trinity, of course. Here’s how he correlates the two:
Because all things flow from the first and most perfect Principle, who is omnipotent, all wise, and all-beneficent, it was most fitting that they should come into being in such a way that their very production might might reflect these same three attributes or perfections. Therefore, the divine operations that fashioned the world machine was three-fold: creation, particularly reflecting omnipotence; distinction, reflecting wisdom; and embellishment reflecting unbounded goodness. (Breviloquium 2.2.2)
God’s power, he goes on to explain, was exhibited in God’s bringing the world into being from nothing “before any day,” his wisdom in his work of distinction over the first three days, and his goodness in his work of embellishment or adornment in the second three days. As he had argued earlier, these three attributes of omnipotence, wisdom, and goodness are “appropriated” by the persons of the Father, the Son, and the Holy Ghost. So, in creating the world in six days, God displayed the Trinity.
Metaphysics of the Music, part 25
With the account I’ve given of Thomas’s views on music, beauty, and the realism of created being as background, I think we are in an ideal position to understand more precisely the metaphysical significance of the music imagery of Tolkien’s creation-myth. In light of the metaphysically tragic reading of the Ainulindalë surveyed earlier, perhaps the first point that stands to be made—as obvious as it is easy to overlook—is the fact that Tolkien places at the origins of his fictional cosmos an act of divine music, which is to say, an act of divine play. This point is made perhaps more clearly in the early edition of the Ainulindalë from The Book of Lost Tales, in which Ilúvatar is actually said to have “sang into being the Ainur…” (BLT 52). From its very inception, therefore, Tolkien’s narrative arguably sets a much more sanguine metaphysical course than the ontological ennui some of his commentators have credited it with.
It is also possible to connect further the Creator’s music-making at the outset of the Ainulindalë with what we saw in chapter one to be the proto-Trinitarianism of Tolkien’s mythical theology. As Tolkien’s puts it in his commentary on the Athrabeth, “the possibility of complexity or of distinctions in the nature of Eru” is already to be glimpsed in the Ainulindalë, particularly in the Flame Imperishable which he identifies as being “in some sense distinct from or within” Eru (Morgoth’s Ring 335, 345). Linking the orthodox doctrine of the Trinity with the musical universalis tradition behind the Ainulindalë, David Bentley Hart has suggested that the “complexity or distinction” of the Christian godhead means that, behind the cosmic music played out in the world by the Creator is the prior divine music which is the Creator, constituting the Creator in his own being:
the image of cosmic music is an especially happy way of describing the analogy of creation to the Trinitarian life. Creation is not, that is, a music that explicates some prior and undifferentiated content within the divine, nor the composite order that is, of necessity, imposed upon some intractable substrate so as to bring it into imperfect conformity with an ideal harmony; it is simply another expression or inflection of the music that eternally belongs to God, to the dance and difference, address and response, of the Trinity. (The Beauty of the Infinite, 276)
In keeping with this point is Ilúvatar’s explanation to the Ainur that it is because they have been kindled with the Flame Imperishable that they are, as it were, to “kindle” their own music, “show[ing] forth [their] powers in adorning this theme, each with his own thoughts and devices, if he will” (Silmarillion 15). It’s possible, in other words, to see the overflowing harmony of divine persons making up the divine being as the basis and originating source for the harmonies produced by the Ainur. And while the finitude and creatureliness of the Ainur’s Music doubtlessly means it must pale in comparison to the “beauty of the infinite” and transcendent rhythms of which the divine godhead is composed, Tolkien’s narrative is less concerned with its status as an inferior redundancy of Ilúvatar’s original theme than it is, as we have also seen, with that respect in which their Music has instead been caught up within and made to share in the divine life and music of Ilúvatar himself. Nor is Ilúvatar in his absolute transcendence in any way oblivious to their Music (as the Neoplatonic One is and must be oblivious, for example, of his emanations), but is rather portrayed as a connoisseur of their Music, delighting in the new state of affairs their Music has brought about: “But I will sit and hearken, and be glad that through you great beauty has been wakened into song” (Silmarillion 15).