The first article of the Belgic Confession (1561) affirms, “We all believe in our hearts and confess with our mouths that there is a single and simple spiritual being, whom we call God.” This confession of God’s simplicity represents the common opinion of reformed theology as well as earlier Christian theology.
But divine simplicity as well as its attendant teachings (immutability, impassibility, timelessness) no longer enjoy such a consensus. Instead, a number of theologians now deny, ignorte, or redefine simplicity. Certainly, the principle of Sola Scriptura allows even the most central teaching of Christianity to undergo scrutiny. Yet I am persuaded that divine simplicity enjoyed such universal consensus because it is biblical, true, and coherent. God is simple.
To deny, ignore, or redefine this doctrine entails not only theological incoherency but also various other inconsisties when it comes to certain attendant doctrines—immutability, impassibility, infinity, triune relations, and monotheism.
The biblical argument against simplicity
The two main arguments against simplicity are: (1) the Bible does not teach it, and (2) the doctrine is incoherent.
The first argument follows the biblicist impulse of the Socianians, Remonstrants, and Arians. The idea is that if a word does not appear in the Bible, then it cannot represent a biblical doctrine.
But since every English word does not appear in the Bible, no word we use appears in the Bible in a 1-to-1 way. Further, words like conversion, the Bible, literal interpretation, historical-grammatical hermeneutics and so on do not appear in the Bible. But these words represent ideas which may appear in Scripture or help us to think through scriptural interpretation.
To give an historical example, the Arians criticized the pro-Nicenes for using the word homoousia because they felt it was unbiblical; but the pro-Nicenes responded that the word represented biblical teaching. The Socianians did the same thing when it came to simplicity. Both actually wanted to remove the foundations from Christian theology so that they could deny Christ’s divine nature.
Evangelical theologians do not want to do that. They, however, pick up the biblicist impulse and affirm: “There is no verse that explicitly teaches that God is simple” (Feinberg 2001: 327). Actually, there are many verses that do. But Christian dogma in any case does not rely on single Bible verses but on the canonical witness to the living God. Were it to rely on a Bible verse citation to make an argument, then it would become an incoherent and inconsistent system.
Theology attests to God who truly exists. It argues from the basis of the whole Bible. It then considers the numerous premises of God across Scripture before making conclusions that represent the whole scope of biblical teaching. Bad theology picks a topic, defines the topic, and lists Bible verses underneath it as if that could prove a doctrine. This method fits confessions because of their representative nature. But do note that Zacharias Ursinus wrote a nearly 700 page theological explanation of his Hiedelberg Catechism!
The incoherency argument against simplicity
The second argument corresponds to the second requirement of true theology, namely, that it represents a reasonable and coherent explanation of truth. Hence, in the modern era, philosophers of religion lead the church against simplicity.
The most compelling argument against simplicity is that it makes God identical to his properties. In this sense, each property is identical to each other (thus not truly different) and God is identical to a property (thus God is a property). But God has differing properties and cannot be a mere property. Therefore, the argument goes, simplicity is not true.
But this argument fails to notice how God’s other attributes provide a fuller explanation of simplicity. In particular, God’s infinite perfection entails that he has one perfect nature which we see refracted according to our finite limitations into the various attributes. Hence, we affirm God’s unicity—his oneness to all that he is.
Second, this argument seems to assume that God would be a property like human love or human knowledge. But that is not the case. God’s Wisdom and Love are subsisting persons in God (the Logos and Spirit), for example. Further, divine properties in a simple and single perfect being differ from our experience of properties since God is supersubstantial—beyond all being. We must consequently affirm that we cannot speak univocally but analogically about God. And besides, that God is identical to his single perfection (which we see according to finite capacities as various attributes) is precisely the claim that simplicity makes.
In the end, we cannot explain an infinite being with finite capacities. God is that which goes beyond finity and into infinity—beyond all being. We must affirm the goodness of apophaticism, that is, we know what God is not; but we can only know what God is (kataphaticism) by analogical reasoning.
The biblical argument for simplicity
The argument for simplicity works like this. The Bible reveals metaphors about God as well as key actions of God that entail his simple nature. Divine simplicity means God has no parts, passions, or possibility. In every modality possible to conceive of, God remains simple. What the Bible reveals about God requires certain conclusions about his nature. These conclusions follow from theological reasoning.
Biblical metaphors for God like “God is light” or “is a consuming fire” or has “no form” (1 John 1:5; Deut 4:24; Deut 4:12) imply a pure nature. To be all light means to admit “no darkness at all” (1 John 1:5) nor “variation or shadow due to change” (James 1:17).
Were we to conceive of some place of pure light without any shadow at all, then that would mean every direction we looked, we would see light. No variation of that light would occur. It would be only and everywhere and at all times light. This metaphor drives us to conceive of God’s nature in some unmixed or pure way.
Second, Genesis 1 and John 1 record that God created everything that came into being. The obvious inference is that God preexisted before all created beings. But if he existed before creation, then he existed before time since time measures movement or change (Gen 1:14).
So whatever else we might say, God’s essence (what he is) and existence (that he exists) cannot be separated. It also means that no other being or thing made God create. No person asked him to create; no thing moved him to act. Since nothing could act upon him to create, then he did not exist in a state of possibility. He acted before all time. The technical word to describe this is pure act.
Further, God created all things from matter and put them into form, while he himself is uncreated. Only created things comprise matter and form. But God is uncreated. So he cannot be a mixture of form and matter. He “is spirit” according to Jesus, which corresponds to his revelation with “no form” (Deut 4:12) or as “a consuming fire” (Deut 4:24). These theophanies pictorially represent that which cannot be seen, namely, “the King of the ages, immortal, invisible, the only God” (1 Tim 6:17).
So far, then, God’s essence and existence seem bound together; he acts without an external cause; and does not comprise matter and form like creation does. We can use sanctified reason to work through these ideas to show their coherency.
The coherency argument for simplicity
By theological argument, I mean that we can use reason to understand biblical revelation and to conclude theological truths from revealed premises. In this sense, sanctified reason simply means doing theology through meditation on Scripture and by the Spirit.
Simplicity means God has no body. This truth coheres because of scriptural revelation (John 4:24) and natural revelation (Rom 1:19–20). Since he is not a body, then he cannot be compromised of form and matter; since these two features mark bodies (Thomas ST I.1.Q3.A2).
From this, it follows that God has no matter but exists in an eternal form. Now, human bodies have form and matter, the latter of which has distinguishable properties in each human. But God does not have such a relationship because he is spirit and uncomposed. He is Life itself (John 14:6; John 5:26).
So Thomas explains, “The relation between Godhead and God is the same as the relation between life and a living thing. Therefore God is His very Godhead” (ST I.1.Q3.A3). Since God has no matter (as we do) and since matter distinguishes us through our properties, the divine form must be identical to its properties—to its Life. God’s nature and essence are the same thing. God is not God with a Godly nature. He is God by nature, whereas we may be named Peter and possesses a human nature.
Now it has to follow that God’s essence and existence are identical. Whatever exists has a cause to move from potentially existing to actually existing. But God has no potency nor did an external cause bring him into existence. He just does: I am what I am (Exod 3:14; see ST I.1.Q3.A4). From these prior conclusions, it is obvious that God cannot stand as a species in a genus. In this sense, there is no complexity to God in terms of genus and species (ST I.1.Q3.A5).
Possibly the most important inference from what has been said so far is that God cannot admit accidents—non-essential properties. In short, God cannot modify his love by adding some external property to himself like adding “dangerous” to “love” because of the incarnation. This would make God’s nature unstable and shifting like a shadow (James 1:17) and question his essential commitment to truth (Heb 6:17–18). Besides, an accident in God would mean that God could potentially be something that he is not; but God is who he is always—so purely actual (ST I.1.Q3.A6).
So what?
God is simple. We worship a simple God. Simplicity begins our union with God and is the end of our union with God. In his simple light, do we see light. God is light. And we will live his ineffable light. His light gives life. It is the light and life of this world. God’s Word is the light that illumines everyone.
But besides being true and the basis for all spirituality (not minor claims!), why should we believe in simplicity?
First, divine simplicity (and divine spirituality) ground the idea of God’s perfection and infinity. To be perfect means to have no imperfection (no shadow in his being). To be infinite means to be beyond all finititute. It follows from divine simplicity since simplicity means God has no parts (so no limit bodily), no passions (so nothing can coerce him in anyway), or possibility (so God always puts his potential to use without fail). God has no limits. And since he precedes all (has no composition which would imply a composer before God) and since he creates all, he must be greater than all; every cause is greater than its effect.
So God is infinite because he has no measurable parts, no capacity for change, and no unrealized potential in the exercise of his powers. He goes beyond all being. He is supersubsantial. He not just is more immense than all; he goes beyond all categories of being.
Infinity applied to God’s being means that God is eternal. Infinity applied to locations in space means omnipresence. Infinity applied to the expanse of space means immensity. Infinity or simplicity reflected upon means that God cannot change (or he’d have been in a state of possibility) nor be changed (thus, impassible).
Since God created as a simple being all things that enter into change, he must by definition be outside of change. Since change measures time, he is timeless. To have change in God would mean to have time in God. But God cannot change. He is timeless.
Had God changed or been in time, then there would be variance due to shadow in him. But there is not. He is pure light, pure act, pure being. Nothing in him implies that he would one day be good, another day not. Nothing in him implies that he might do us good and then decide not to.
In these ways, simplicity grounds God’s perfection, infinity, eternality, immensity, omnipresence, immutability, impassibility, and impassibility. It is also the only way to make sense of our worship of Jesus. If we are monotheists, then how can we worship Jesus and God? The answer is that God is simple and Jesus (or the Son) subsists simply in the divine essence. So triune relations only make sense when we affirm simplicity. Otherwise, we would find nearly impossible to remain monotheists and worship Jesus. Simplicity is a basic assumption of triune theology.