“From first to last,” writes philosopher Brian Davies, “the doctrine of divine simplicity is a piece of negative or apophatic theology and not a purported description of God” (“Classical Theism and the Doctrine of Divine Simplicity,” in Language, Meaning and God, p. 59). That is to say, it belongs to the necessary theological task of properly distinguishing the Creator from creation. Sounds easy. All we need to do is to think of God as a person and then add a bunch of omni-attributes. But this personalist approach only leads to our thinking of God as a Superman on the same plane of ontological existence as the rest of us—and that just can’t be right. Hence it is unsurprising that from very early on we find Christian thinkers employing the via negativa: we cannot say what God is, only what he is not. Most theologians, of course, have not been content to restrict themselves to the silence of the via negativa and have advanced various justifications for cataphatic statements about God, the two most famous being Dionysius’s rendition of the divine names and St Thomas Aquinas’s theory of analogy. If Davies is correct, we should interpret divine simplicity not as a positive description of the divine nature but as refusal to import creaturely categories into the Godhead. Unlike finite beings, the uncreated Creator is not composed of parts, whether physical, temporal, or metaphysical. Or as Davies provocatively puts it: “God has no nature in any intelligible sense. He is divinity through and through without parts or aspects. … Everything that God is is God” (p. 51).
Consider physical objects. We take a juicy steak off the grill and immediately slice it with a knife, put a piece into our mouth, chew it and swallow it. Very quickly that piece of steak is broken down and assimilated into our bodies. Hours later the waste products are expelled. The steak no longer exists. Not only was it divisible, but it was dissoluble.
Now consider that steak from a metaphysical perspective. It has a nature that differentiates it from other entities in the universe. It is one kind of thing and not another kind of thing—a steak and not a potato, my rare steak in Roanoke and not your over-done steak in Dallas. A steak, any steak, is composed of accidental and essential properties. Take away one or more of its accidental properties, and it becomes a different kind of steak; eliminate one or more of its essential properties, and it becomes something different altogether.
God, the doctrine of divine simplicity announces, is incomposite and indivisible. He is not like any thing that we know in this world. If he were, he could not be the ultimate source and cause of all that exists. William Vallicella elaborates: “God is radically unlike creatures in that he is devoid of any complexity or composition, whether physical or metaphysical. Besides lacking spatial and temporal parts, God is free of matter-form composition, potency-act composition, and existence-essence composition.” This all sounds technical and abstruse, but one does not have to have a firm grasp of these philosophical distinctions (I certainly do not) in order to glimpse the decisive significance of the doctrine. “Simplicity,” James Dolezal declares, “is the ontologically sufficient condition for God’s absoluteness” (God Without Parts, p. 2). Aquinas puts it this way:
Every composite, moreover, is subsequent to its components. The first being, therefore, which is God, has no components. Every composite, furthermore, is potentially dissoluble. This arises from the nature of composition, although in some composites there is another element that resists dissolution. Now that which is dissoluble is in potentiality to not-being. But this cannot be said of God, since of His very essence He is necessarily. There is, therefore, no composition in God. Every composition, likewise, needs some composer. For, if there is composition, it is made up of a plurality, and a plurality cannot be fitted into a unity except by some composer. If, then, God were composite, He would have a composer. He could not compose Himself, since nothing is its own cause, because it would be prior to itself, which is impossible. Now, the composer is the efficient cause of the composite. Thus, God would have an efficient cause. Thus, too, He would not be the first cause—which was proved above. (Cont. Gent. I.18)
To make the point a bit clearer, consider what the denial of divine simplicity must logically entail. If God is a complex being, then he is not in fact the unconditioned Absolute but an entity made up of parts, properties, and aspects that are metaphysically prior to him and upon which he ontologically depends. A molecule of water is composed of two atoms of hydrogen and one atom of oxygen—H2O. Water depends upon these constituent atoms to be water. In similar fashion, if God is a metaphysical conglomerate, then he too depends on his constituent parts in order to be himself. They are more ultimate and fundamental than he is. “The basic logic,” Dolezal explains, “is that if God were composed of parts he would, in some sense, depend upon those parts inasmuch as those parts would be indispensible to the explanation of his existence and essence” (p. 72). Of a composite deity we may ask: Who composed him? What keeps him in existence? Why can’t he be decomposed? That such questions even occur to us demonstrates that complex divinity cannot be the self-existent, transcendent Creator whom Christians have always confessed. As St Irenaeus wrote in the late second century:
God is a simple, uncompounded Being, without diverse members, and altogether like, and equal to himself, since He is wholly understanding, and wholly spirit, and wholly thought, and wholly intelligence, and wholly reason, and wholly hearing, and wholly seeing, and wholly light, and the whole source of all that is good—even as the religious and pious are wont to speak concerning God. (Adv. Haer. 2.13.3)
In its negative function the doctrine of divine simplicity does not commit one to a specific construal of the trinitarian unity and aseity. It does not commit one to a Thomist understanding of the divine essence (God is his existence), as opposed to a Scotist understanding (God is infinite Being); nor does it automatically exclude Byzantine formulations of the distinction between the divine essence and energies. Nor does it render unsayable essential Christian assertions, such as the dogma of the Holy Trinity. What it does do is enable us to conceive God as God and not as a godlet or demiurge.
Hence we are not dealing here with an arcane piece of philosophical speculation irrelevant to the gospel. In his essay “The Simplicity of the Living God,” Christopher Franks protests the way contemporary philosophers and theologians have addressed the topic, the former treating it as a metaphysical conundrum, the latter as a non-biblical accretion. Both have failed to see how the doctrine flows from and undergirds a specifically Christian understanding of God as Creator and Redeemer: “Simplicity teaches us how to think about a God who is the fully Living One, the one who lives so fully and completely that this Life is uncontradictable. This God is the source of life for others, and precisely as cause of being, this God is fully free to create (or not to create), free even to enter into union with creation, even the intimate union of the Incarnation, without abandoning that Life” (p. 276).
As an expression of apophatic theology, the doctrine of divine simplicity might be best understood, suggests Davies, as a grammatical rule: “To cast things in a more modern idiom, the Thomist doctrine of divine simplicity is an exercise in ‘logical grammar’; its aim is to tell us the sort of conclusions about God which are not to be drawn” (p. 59). Yet by telling us what divinity cannot be, the doctrine also clears a space for us to proclaim and indwell the one God of biblical revelation—Father, Son, and Holy Spirit.