Some form of the doctrine of divine simplicity has long been an assumed mainstay in Christian theology. At its base, it affirms that God is not composite, or composed of metaphysical parts. In some of its most robust forms, it entails a lot more, such as the idea that God is identical with his attributes. Or that God is not composed of potentiality and actuality, or genus and difference, and a host of other distinctions. God is simple, devoid of any complexity in his being.

Now, this has come in for all sorts of criticisms from all directions, especially over the last 100 years, saying it denies God’s ability to exercise free choice, it’s a philosophical hot mess, and even disallows the distinctions necessary to affirm that God is Triune. These are all strong charges, but one that seems particularly troublesome for Protestants is that it doesn’t appear to be obviously taught anywhere in Scripture.

On a simple read, there’s no prominent text that says, “God is simple”, or “God has no parts”, etc. Which is one of the reasons many have come to think such an apparently abstract, non-intuitive doctrine is sadly nothing more than the intrusion of static, Greek substance metaphysics into the dynamic, Biblical presentation of God. If that’s the case, then why bother with it? Especially if it has the potential to cause a host of other problems?

For those who take Scripture as the ultimate norm for our doctrine of God, then, the question becomes how could anyone go about claiming it is a Biblical doctrine?

Well, one way to go about it is the way Steven Duby does in his recent, rigorous dissertation (now monograph) Divine Simplicity: A Dogmatic Account. In the work, Duby pays attention to a number of other attributes he sees explicitly taught in Scripture, reflects on them, and then demonstrates the way they imply or demand a strong account of simplicity.

He gives a helpful summary of it in his conclusion:

God’s singularity implies that he is himself the fullness of his deity subsisting,  that he transcends the categories of genus and species, that he is really identical with each  of his perfections and is therefore not composed of substance and accidents, and that he is  without composition altogether in the uniqueness with which he is God. God’s aseity implies that he is actus purus, ipsa deitas subsistens, ipsum esse subsistens, really
identical with each of his own perfections, and free from all composition with nothing
back of him governing or actualizing his being. Likewise, God’s immutability implies
again that he is wholly in act, without potentia passiva whereby he might be altered or
enhanced. In his self-sameness and indivisibility, he is each of his perfections subsisting,  without accidents and without any composition whatsoever. God’s infinity too implies that he is actus purus. In his boundless perfection, each of God’s attributes is really identical with his essence, and each of the divine persons is really identical with his essence subsisting in a certain manner. Finally, the act of creatio ex nihilo implies that God is actus purus and ipsum esse subsistens without any eternal co-existents. Just so, the simple triune Creator is the self-efficacious and ultimate origin of all that exists. –Divine Simplicity: A Dogmatic Account, 235

This is just the summary, of course, but you can begin to see how it works. That God is a se, independent, the one who does not need or depend on anyone or anything outside of himself to be what he is, seems fairly demonstrable from Scripture. But then we have to stop and think out the implications of what that means.

In the case of each of the attributes like aseity, Duby spends a significant amount of time showing that implies that nothing outside of God’s Triune life activates some potentiality within him, in which case he’s not composed of actuality and potentiality, but only pure actuality (ie. he is actus purus). It also implies that he can’t be composed of his attributes or posses them in such a way that he instantiates or depends on attributes that logically precede him, otherwise he would be dependent on them to make him what he is. And from there you go down a line of inferences to which a strong account of simplicity is the proper conclusion.

We might say that on Duby’s account, simplicity isn’t a “biblical” doctrine in that it is “expressly set down in Scripture”, but it it is one which by “good and necessary consequence may be deduced from Scripture” (Westminster Confession of Faith 1.6). It’s something of a composite judgment about who God is if all that Scripture says about God is to be true.

Much Trinitarian theology functions in this way. Various strands of Biblical testimony to God’s unity, the joint activities of Father, Son, and Spirit, their distinctness, and so forth, are all considered and gathered together. Upon much reflection on what they all could mean in unison, what the relationships between the person can or cannot be like if all of Scripture is true, then a judgment is rendered.

Of course, it may be the case the chain of reasoning from the Scriptural affirmations about God’s aseity or immutability to simplicity are not as strong as Duby thinks. Maybe at key points certain philosophical assumptions have snuck in with the sound, biblical premises. Or it could be that his replies to other sorts of objections prove ineffective. But it’s not apparent to me that a case of this sort can be ignored, or written off as only so much bad philosophy by Protestants.

Soli Deo Gloria