Alving Plantinga’s criticism of Aquinas’s Doctrine of Divine Simplicity cannot be ignored since currently numerous philosophers and theologians follow him regarding the downplaying or rejecting DDS. In fact, engaging Plantinga’s arguments against DDS is a needed step in order to explore whether divine simplicity can be recorded in the analytic tradition. Embracing a non-constituent ontological framework where human concepts can apply univocally to God despite the limitations of human language (p. 18), Plantinga explores how God relates to abstract properties and the conflict between DDS and attributes such as aseity and sovereignty. Plantinga discusses Aquinas’s doctrine of simplicity and offers his reasons it is philosophically incoherent. He begins his section on simplicity noting that the Christian tradition has given an affirmative response to whether God has a nature. Plantinga also recognizes that classic theism has also understood God’s essence (his nature) as equal to God’s existence. He writes,
The basic idea of this doctrine is that no distinctions can be made in God. We cannot distinguish him from his nature, or his nature from his existence, or his existence from his other properties; he is the very same thing as his nature, existence, goodness, wisdom, power and the like. (p. 27)
Although Plantinga partially agrees with the classic tradition in affirming that God has a nature (p.7), he departs from it in the sense that he does not think God’s nature can be equated with his existence, as Aquinas argues. For Plantinga, the doctrine of simplicity “is a dark saying.” (p. 27) First, the doctrine is difficult to grasp. Second, in his view, there is no clear reason the modern theologian should accept it. Plantinga focuses on this second aspect and argues that Aquinas defended divine simplicity because the latter believed that rejecting it would compromise the notion of aseity and the sovereignty of God and would make God depend on external properties. Let me explain. In his reading of Aquinas, Plantinga argues one reason Aquinas defended the doctrine of simplicity was the accommodation of God’s attributes, specifically aseity and sovereignty. The idea behind such a purpose was the fear that a rejection of divine simplicity would compromise God’s aseity and the independency of God on external components (p. 28). If God has a property and such a property is distinct from him, then God would depend on it.
The argument Plantinga offers against DDS is that if one claims the idea that God has a nature and a series of properties while holding DDS, then God would be identical to those properties. In this way, God would not be a person as the Christian faith claims, but a property. This creates a conflict: a property cannot create the world. The issue that arises here is twofold. First, God would necessarily depend on his essential properties for his existence. Second, God would be unable to control those properties (p. 33). The issues with divine simplicity do not stop here.
If [God] had properties and a nature distinct from him, then he would exist and display the character he does display because of a relation in which he stands to something other than himself. (p. 33)
According to him, this scenario “doesn’t fit” with the doctrine of God’s aseity. For these reasons, Plantinga doubts that simplicity is a potential solution to the aseity-sovereignty problem. It seems that for him Aquinas’s solution that God’s essential properties are literally in him is not very convincing.
In this respect, Plantinga embraces the idea that God could be independent from his properties and introduces Plato’s Forms (properties, propositions, and such like) that might be essential and exist necessarily (p. 35).That is, these Forms would be independent of God. However, this potential solution enters into conflict with God’s sovereignty. For Plantinga, this opens the door for considering nominalism as an alternative solution to the aseity-sovereignty issue. Plantinga’s introduction of Platonic Forms and their appropriation might be problematic in some theological circles. The nomalist approach (the rejection of the existence of properties) is not free of controversy either. Plantinga recognizes that Aquinas’s discussion does not endorse nominalism because for Aquinas, God’s properties and God himself are the same thing. Despite this, Plantinga agrees with Aquinas in some parts, especially when one defends God’s immateriality and the idea that God has a nature.
What Plantinga finds problematic is Aquinas’s claim that in God there are no accidents, understanding this as the belief that “God has no accidental properties.” (p. 39) The reason behind such an assertion is that any accidental property that God might have could limit and condition Him. Here again it raises the issue of how Plantinga and Aquinas understood the term ‘property’ and to what extent God is limited. For Aquinas, not all propositions about God predicate a property of God. For example, in Aquinas’s view, the proposition that <God created Adam and that he knew he sinned> does not mean such a proposition is a property of God. This does not characterize God’s nature at all because God’s properties should be non-relational. (p. 42) Plantinga argues that this reasoning leaves a lot to be desired. First, the proposition <God created Adam and that he knew he sinned> characterizes both God and Adam. Although this proposition could not be a property, it is like a property. (p. 43) Second, the issue of potentiality-actuality raises here as well in relation to DDS. For Aquinas, divine simplicity holds that there is no composition of properties. Plantinga claims that the proposition that <God is not merely good, but He is goodness> is not easy to grasp. If God is identical with His properties, then each property is identical to each other. This would mean that God would only have one single property: Himself (p. 47) The consequence of such an assertion is that God would not be “a person but a mere abstract object; he has no knowledge, awareness, power, love or life.” (p. 47)
To avoid the apparent incoherent statements aforementioned, Plantinga concedes that perhaps Aquinas’s understanding of <God is good> does not mean that <God is goodness> but that <God is his goodness> or <his life>, and such like. This makes us distinguish between a property and the state of affairs of an object displaying a property. In this respect, as Plantinga notes, we could read Aquinas as he speaks of states of affairs in God: “For any properties P and Q in God, God’s having P is identical with Gods having Q and each is identical with God.” (p. 49)
Although speaking of ‘states of affairs’ in God is a plausible solution to the simplicity issue in Aquinas, Plantinga is aware that Aquinas himself did not speak of this at all. Therefore, this potential solution is speculative and might be untenable in the end.
However, there is the possibility of speaking of equivalent propositions in Aquinas’s discussion of divine simplicity: “If A and B are logically equivalent, i.e., true in the same possible worlds, then A is identical with B. And if this can be held with some show of plausibility for propositions then surely the same goes for state of affairs.” (p. 50) This alternative solution answers some questions raised by Plantinga, but it is still problematic: “Either God has no nature or else God is not genuinely sovereign.” (p. 50) Nonetheless, with this modified version, God would also be a ‘state of affairs.’ This is also problematic because if this proposition is true, then God would not be a person but an abstract object as we discussed earlier (p. 53). It is worth noting that Plantinga is aware that he might be misunderstanding Aquinas. This raises the possibility that there are other interpretations of Aquinas that might avoid Plantinga’s criticism. In the end, perhaps Aquinas means — Plantinga believes — that “God is identical with his essence, with his goodness, with goodness itself, and the like, he does not mean to identify God with a property or state of affairs at all, but with some quite different.” (p. 53) Although it is difficult yet possible to identify that “quite different,” Plantinga decides to reject DDS because apparently it is “flouting the most fundamental claims of theism.”