Thomas Torrance picks up on the Athanasian idea that God has always already been Father, Son, and Holy Spirit but that becoming Creator was something new for God. As we dig further into Athanasius’s theology itself, as told by Thomas Weinandy, what we see behind this is how this notion took place within Athanasius’s defense of the homoousion language Contra Arionos relative to both a doctrine of creation and how soteriology is understood within that frame; a Christologically induced frame grounded in the intra-Trinitarian life of God. Honestly the way Weinandy unfolds all of this is one of the most profound things I have ever come across in regard to answering the question of why God would create in the first place; in other words, how does creation itself flow organically from the who God is in his inner and eternal life (in se)?
As Weinandy details it is precisely because God is Father of the Son, and Son of the Father by the Holy Spirit (that: by the Holy Spirit is my addition) that creation makes sense; i.e. there is place for the other in God by nature (or ‘being’ ousia). In other words the fact that God is, by nature, Father, Son, and Holy Spirit allows for the type of space to conceive of a God who could create ‘others’ if he wanted to; i.e. he’s a God, eternally so as revealed in Christ (the Son), who is relational—i.e. his oneness (De Deo uno) is given shape by his threeness (De Deo trino), and vice versa. A God who is Pure Being, or monadic, like the God of Islam or the Modalists, or of Arius, would never create, not for any theo-logical reasons anyway.
Let’s get to it, here’s how Weinandy unfolds all of this in Athanasius’s theology (the quote is lengthy):
The central soteriological issue in Athanasius’ Contra Gentes and De Incarnatione was creation. Athanasius continues to stress within his anti-Arian and pro-Nicene writing that is only because the Son is truly divine that the Father creates through his so that creation always possesses an intimate and immediate relationship with the Father through the Son. Employing Irenaeus’ famous analogy, Athanasius states that the Son is ‘the hand’ though [sic] which the Father brings into being all that is. This is again the theological basis upon which Athanasius founds the Father’s love for humankind and the Son’s innate responsibility, in the light of sin, for humankind’s subsequent redemption. ‘It is fitting that redemption should take place through none other than him who is Lord by nature, lest, though created by the Son, we should name another Lord.’ Thus, unlike Arianism, there is no need for an intermediate cosmological third party that bridges the ontological gap between the Father and creation, for the Son, through whom the Father creates, unites in an unmediated manner, in that he too, is God, the whole creation to the Father.
Moreover, in response to the Arian claim that the Son is a creature, Athanasius innovatively asks a veryinsightful and new question. How can God be ‘Creator’ if he is not first ‘Father’? ‘If the divine essence is not fruitful in itself but barren, as they hold, as a light that does not lighten or a dry fountain’, how is it that it can give being and life to others? For Athanasius, only if God is eternally the fruitful Father who, by the very nature of who he is, eternally begets his Son, is it possible for the Father, by his will, to create through his Son. ‘If then that which comes first, which is according to nature, did not exist, as they would have it in their folly, how could that which is second come to be, which is according to will? For the Word is first, and then the creation.’ However, since the Father has created, this manifests that he is inherently fruitful by nature and so he is first of all Father of the Son. ‘If he, by willing them to be, frames things that are external to him and before were not, and thus becomes their maker, much more will he first be Father of an offspring from his proper essence.’ If creation is the foundation of all soteriology, then, for Athanasius, its requisite is found only within the fruitful creativity of the Father begetting the Son.
This is a marvelous insight. If God was simply a singular existing being – a monad, something after the manner of Aristotle’s ‘self-thinking thought’, then God could never conceive of anything other than himself. Being simply One, it would be metaphysically impossible for him to conceive of two, or of three, or of an infinite multitude, for One is all there is. Actually, God would not even conceive of himself as One because ‘One’ itself implies a further numerical sequence of others. We only know what ‘one’ means because we equally know what ‘two’ means, without ‘two’, ‘one’ not only has no meaning, it is also, literally, inconceivable. God would just be and nothing more could be conceived, imagined, or said. As Athanasius rightly perceives, only if God is, by his very nature, the Father begetting the Son, could that God conceive of bringing into existence other beings that are not God.
Much richness to consider.
One way to reflect on this, at least one way that I’d like to, is to note the theological taxis or ‘order’ present in all of this. It all starts with the Triune God as the ground and grammar of everything else; which is given shape by a Christological conditioning in regard to who we know God to be as Father of the Son, and as such we only have the capacity to know God as the Creator in this way first; i.e. as Father of the Son and Son of the Father. It is this basis upon which creation can be conceived of theo-logically, as the Father is understood to be, coinherently, as eternally fruitful; since that’s what Fatherhood entails, i.e. in having a Son. From this creation gains its telos or ‘purpose’, it is a Christologically oriented trajectory. And from within this frame we can finally have a discussion about everything else—like salvation, a doctrine of Scripture, so on and so forth—since everything else as far as we’re concerned requires created reality given the fact that we’re creatures coram Deo (‘before God’).
Let’s leave off there. But it is quite astounding, really, to see how thinking things from a Trinitarian ground, and one that is Christological conditioned, as Athanasius originally did, provides such rich and fertile soil to think about everything else that is subsequent; i.e. meaning all else that we might want to call “theology.”
 This insight comes directly from Thomas G. Weinandy.
 Thomas G. Weinandy, Athanasius: A Theological Introduction (Hampshire/Vermont: Ashgate Publishing Limited, 2007), 79-80.