One, Undivided: The Classical Doctrine of Divine Simplicity and Why Craig Gets It Wrong

The doctrine of divine simplicity is one of those positions that sounds counterintuitive the first time you encounter it, and then, once it clicks, you start wondering how anyone could seriously think otherwise. The claim, stated in its classical form, is that God has no parts. No division between His existence and His essence, no real distinction between His attributes, no gap between what He is and that He is. His wisdom is not a property He happens to possess; it just is God, considered under a certain mode of description. Same with His love, His power, His holiness. You are not adding things together when you speak of God. The Augustinian instinct behind this was solid: if God were composed of parts, those parts would in some sense be prior to God, and then you've got an explanatory regress and, worse, a god who owes his existence to something other than himself. Aquinas systematized the intuition in the Summa Theologiae Ia, q. 3 with his trademark precision, but the roots go back through the Greek Fathers, Pseudo-Dionysius, Augustine's De Trinitate, and behind all of them to the Platonic inheritance that the early church both baptized and corrected. The Second London Confession captures it economically: God is "most holy, most free, most absolute... without body, parts, or passions."

The doctrine matters for reasons that are not merely philosophical housekeeping. If there are real distinctions in God between, say, His love and His justice, then you have a god whose attributes potentially stand in tension with one another. You also have a god who can change, since a being with a genuinely composite nature is, at least in principle, subject to rearrangement. Simplicity is what underwrites divine immutability and impassibility. Pull it out and both go wobbly. It also does crucial work in trinitarian theology: the three persons are distinct, but the divine essence is not divided among them, which is why the Cappadocians and later the Latin tradition could insist on one God without collapsing into modalism or tritheism. There is a reason the councils kept returning to this. It is not a philosophical hobby horse; it is structural load-bearing wall.

William Lane Craig finds it unlivable. His "neo-classical theism" wants to affirm God's greatness while jettisoning what he takes to be the excesses of the Thomistic tradition. The core of his objection is that simplicity, strictly construed, seems to make God identical with His attributes, and those attributes identical with one another, which then seems to make the abstract properties themselves divine. Worse, if God just is His existence, there is no room for the distinction between the divine persons that Trinitarian orthodoxy requires. Craig argues that divine simplicity, rather than protecting monotheism, actually threatens it by conflating God with the Platonic abstracta he supposedly grounds. He prefers a model where God has genuinely distinct properties while remaining without physical parts.

The objections are not silly, but they rest on a misreading of what the classical doctrine actually claims. Aquinas was not saying that Wisdom-as-such and Justice-as-such are two names for the same abstract object, and therefore God is identical with an abstract object. The claim is that the distinctions we draw between divine attributes are distinctions of reason, arising from our creaturely mode of apprehension, not real divisions in the divine being. We approach an incomprehensible reality through multiple conceptual angles because our minds are finite, not because God is divided. This is entirely compatible with a robust doctrine of the Trinity, where the personal distinctions are real but the essence remains one and uncomposed. Gilles Emery's work on Thomas and the Trinity has shown, painstakingly, that simplicity and the relational grammar of Trinitarian theology are mutually reinforcing rather than in conflict, because the persons are constituted by their relations of origin, not by being portions of a divisible substance. Craig's worry about abstract objects is also somewhat beside the point: classical theism grounds the forms in God's intellect, not the other way around, which is precisely the anti-Platonic move Augustine made in De diversis quaestionibus 83, question 46.

What Craig offers as a replacement ends up conceding more than it gains. A God with genuinely distinct properties, properties that are not identical with his essence, has those properties contingently or necessarily. If contingently, then God's goodness is something He might lack, which is incoherent. If necessarily, you have to explain why a God constituted by multiple irreducibly distinct properties is still metaphysically simple enough to be "God" in any theistically meaningful sense. The classical tradition's answer was already there: God's attributes are distinguished only according to our manner of conceiving, not according to any real composition in God. Craig never quite escapes that problem; he relocates it. The medievals were not naive about these pressures. Simplicity was not an afterthought; it was the considered response to precisely the kind of regress Craig's model quietly re-introduces.