Earlier this year I received the following thoughtful question from DG (as I will refer to him) about the argument for God from logic, which I quote in full:
In his essay [in Beyond the Control of God?] Professor Welty points out that in TCR [Theistic Conceptual Realism] “objectivity is secured by there being just one omniscient and necessarily existent person whose thoughts are uniquely identified as AOs.” But how do we get to this one from within the confines of a TCR approach alone? And in “The Lord of Non-Contradiction” you and Professor Welty state: “If the laws of logic are necessarily existent thoughts, they can only be the thoughts of a necessarily existent mind.” Here we go from plural thoughts to a singular mind as we do in the conclusion: “But if there are necessarily existent thoughts, there must be a necessarily existent mind; and if there is a necessarily existent mind, there must be a necessarily existent person.” But why not minds or persons? In note 31, you partially address my concern: “It might be objected that the necessary existence of certain thoughts entails only that, necessarily, some minds exist. Presumably the objector envisages a scenario in which every possible world contains one or more contingent minds, and those minds necessarily produce certain thoughts (among which are the laws of logic). Since those thoughts are produced in every possible world, they enjoy necessary existence.” You then show how this option fails and I agree. But what excludes many necessary beings each of which sustain some necessary truths? This is certainly ontologically extravagant and, as Adams notes in his book on Leibniz (p. 181), perhaps we can simply appeal to Ockham’s Razor to deduce one mind. But he adds, and I agree, that “a more rigorous argument would be desirable”.
At first I thought we could, as Quentin Smith suggests in his essay “The Conceptualist Argument for God’s Existence”, claim that the actual world is an infinite conjunction of all true propositions and that such a proposition, following conceptualism, could only be an accusative of one omniscient mind. But to claim there is such an infinite conjunctive proposition that needs a mind to account for it, given the view that propositions are mental effects, seems to assume there is an infinite mind who is thinking the infinite conjunction. Thus the addition of the actual world in the argument appears to beg the question.
I also considered Leibniz’s argument that without one divine mind we can’t account for how necessary truths “can be combined, any one to any one, because any two propositions can be connected to prove a new one”. But here we also seem to presuppose one mind sustaining the infinite conjunction of necessary truths that we discover in our finite combinations. Pruss, in his discussion of Leibniz’s approach, brings in a possible worlds option by pointing out that “the idea of a possible world will contain the ideas of all other possible worlds since at that world it will be true that they are possible” (Actuality, Possibility, and Worlds, 207). But wouldn’t we need one omniscient mind intending the world ensemble that is supposed to help us infer there is one omniscient mind thinking the ensemble?
I suppose we could appeal to a premise that states it is impossible for there to be a necessarily existing mind different from God. But this doesn’t seem persuasive to me at the moment.
As I understand it, the objection can be boiled down to this. Even granting that we’ve shown that necessary truths (such the laws of logic) presuppose a necessarily existent mind, it doesn’t follow that these truths are grounded in only one such mind. As DG puts it:
But what excludes many necessary beings each of which sustain some necessary truths?
An obvious first move would be to appeal to the principle of parsimony. We should not multiply entities beyond necessity. If necessary truths need to be grounded in a necessarily existent mind, then one such mind will suffice. There’s no explanatory need for further minds. But I also agree that “a more rigorous argument would be desirable,” so what follows is a preliminary sketch of one.