Combining Aquinas and the MOA
Here is a variation on my argument from Anselm to Plantinga:
P1) Possibly, there is an absolutely metaphysically simple being.
P2) Necessarily, that there is an absolutely metaphysically simple being implies that there is a maximally great being.
P3) If it’s possible that something is maximally great, then it’s possible that necessarily there is an omnipotent, omniscient, and omnibenevolent.
C) There is an omnipotent, omniscient, and omnibenevolent being.
Defense of P1: An absolutely metaphysically simple being, insofar as it is being, is attributed positively, cannot contain a part that negates its essential nature, which means it does not contain inconsistent properties or attributes. Now, it has been objected, by none other than Plantinga, that the concept of a metaphysically simple being is incoherent, but as Vallicella (2019) points out, one need not adopt the metaphysical framework by which that incoherence is pressed. Thus the metaphysical possibility of an absolutely metaphysical being will depend on the supposition of a “constituent” metaphysical frame work. Vallicella (2019) writes, the “constituent” metaphysicians “…did not think of individuals as related to their properties as to abstracta external to them, but as having properties as ontological constituents.” This roughly tracks Aristotelian realism over Platonic realism, which I think is a decisively preferable metaphysical framework, given the third-man objection to Platonism. With these considerations in mind, I think it is highly plausible to defend the metaphysical possibility of an absolutely simple being.
Defense of P2: Aquinas demonstrates that an absolutely metaphysically simple being is metaphysically necessary (since its has existence essentially, see -), omnipotent (since God is infinite, which is derived from His simplicity), omniscient (see, in particular, ), and the good of every good (see ) and the highest good (see ), so omnibenevolent. Now one might object that a maximally great being has many divine attributes and is, therefore, not absolutely metaphysically simple, but Aquinas explains that the plurality of divine attributes is not opposed to divine simplicity. Since the attributes of a maximally great being can be deduced from an absolutely simple being, we can conclude that the existence of an absolutely simple being necessarily implies an maximally great being (where maximal greatness is defined as a necessarily existing, omnipotent, omniscient, and morally perfect being).
Defense of P3: This implication follows from Plantinga’s stipulative definitions of maximal greatness, and maximal excellence, with a slight deviation from moral perfection to omnibenevolence, defined in Thomistic terms. So this is an analytically true implication.
Mx ≝ x is maximally great
Ox ≝ x is omnipotent, omniscient, and omnibenevolent
Sx ≝ x is absolutely metaphysically simple
Theorem of K: ☐(p → q) → (♢p → ♢q)
Theorem of S5: ♢☐p → ☐p
Axiom M: ☐p → p
1. ♢(∃x)Sx (premise)
2. ☐[(∃x)Sx → (∃y)My](premise)
3. ♢(∃y)My → ♢☐(∃z)Oz (premise)
4. ☐[(∃x)Sx → (∃y)My]] → [♢(∃x)Sx → ♢(∃y)My] (Theorem of K)
5. ♢(∃x)Sx → ♢(∃y)My (2,4 MP)
6. ♢(∃y)My (1,5 MP)
7. ♢☐(∃z)Oz (3,6 MP)
8. ♢☐(∃z)Oz → ☐(∃z)Oz (Theorem of S5)
9. ☐(∃z)Oz (7,8 MP)
10. ☐(∃z)Oz → (∃z)Oz (Axiom M)
11. (∃z)Oz (9,10 MP)
Vallicella, William F., “Divine Simplicity”, The Stanford Encyclopedia of Philosophy (Spring 2019 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/spr2019/entries/divine-simplicity/>.