In what follows I propose yet another argument for theism. Here God is understood as an intelligent being, that is, a subject, that is the root of reality. The first premise of the argument has it that the whole of reality is knowable. Now, if the whole of reality is knowable, and if knowing something is essentially a matter of being subjectively acquainted with it, then everything that exists is understandable or comprehensible.
In other words, everything that exists is an intelligible being. An intelligible being is a being with which at least one intelligent being can be subjectively acquainted. Intelligent beings include but are not necessarily limited to human beings. A limitation to human beings would in fact be quite ad hoc and gratuitous. There is no reason at all to believe that everything that exists is knowable by humans. Such a belief would be highly pretentious and entirely unwarranted.
So reality is exhaustively akin to intelligibility. The whole of reality is inherently intelligible. But then the metaphysical ultimate is intelligible as well. Reality is grounded in intelligibility. The origin of being, the root of reality is intelligible. An intelligible being thus grounds reality.
If the root of reality is an intelligible being, then it is a being with which at least one being can be subjectively acquainted. Since a being that is not the root of reality cannot be subjectively acquainted with the root of reality, a being that can be subjectively acquainted with the root of reality must be the root of reality itself. So the root of reality is in fact a being which can be subjectively acquainted with a being. Hence the root of reality is not only an intelligible being, a being that can be known, but it is in fact an intelligent being, a being that can know. Hence the root of reality is a subject. Thus God exists.
In short, since the root of reality is intelligible, it must be possible for there to be a being that is subjectively acquainted with the root of reality. And since only the root of reality could possibly be subjectively acquainted with the root of reality, it follows that said being can only be the root of reality itself. So the root of reality cannot merely be an intelligible being. It must be an intelligent being and theism follows.
One might object that it only follows that there is a possible world within which the root of reality is a subject. It presumably doesn't follow that the actual world's root of reality is a subject. I reply that it does in fact follow that the actual world's root of reality is a subject. For the actual world's root of reality is also the root of reality in that possible world. Since the root of reality in that possible world is a subject, it follows that the actual world's root of reality is a subject.
The argument shows how epistemic optimism entails theism. It's first premise has it that the whole of reality is knowable. It is the same as the first premise of the modal-epistemic argument for God's existence I developed years ago. Both arguments are thus connected. They are allies that explore the same idea: the purported unknowable is in fact not unknowable at all. It's knowable. As part of the defense of my modal-epistemic argument I provide a range of reasons for accepting the first premise. Let me add one additional reason. Plausibly, the relation between the knowable and the real is perfectly natural. There is no peculiar mysterious or arbitrary brute split between the knowable and the unknowable. But then either the whole of reality is knowable or reality isn't knowable at all. The latter seems false. For at least some things seem to be knowable. In fact, some things are in fact known, namely by human beings. It thus follows that we may reasonably hold that the whole of reality is knowable. There is a perfect parallelism between the order of knowledge and the order of being. The knowable and the real coincide. All that 'is' can be known.
The relation between such fundamental notions as the knowable and the real is indeed plausibly no less natural than the perfectly natural relation between, say, such foundational concepts as matter and space, or abstract objects and causally efficacious objects. All that is material is in space or nothing material is in space. There isn't a middle ground. All abstract objects are causally efficacious or none of them are. There is no intermediate position either. Similarly, all that exists is knowable or nothing is knowable. Since some things surely are known, everything that exists is knowable. The first premise is cogent.
But what about my claim that only an intelligent being that is the root of reality can be subjectively acquainted with the root of reality? One might object that perhaps the root of reality is an intelligent being, and if so, it could maybe (for example by revelation) establish that another intelligent being becomes subjectively acquainted with it. This might be so, but if so I adjust my argument as follows. Suppose for reductio that the root of reality is not an intelligent being. In that case said option is off-the-table. My claim now becomes more modest. If the root of reality is not an intelligent being, no intelligent being can be subjectively acquainted with the root of reality. This contradicts the first premise of my argument, namely the premise that all of reality is knowable. Hence it follows that the root of reality is an intelligent being. That is to say, God exists. Should the objector persist, "Why is it impossible to be subjectively acquainted with the root of reality in case the root of reality is not an intelligent being?" I answer that the second premise of my modal-epistemic argument (that I defend thoroughly as part of my development of the modal-epistemic argument) has it that it is impossible to know that God doesn't exist, while being subjectively acquainted with (and thus knowing the nature of) a root of reality which isn't an intelligent being entails knowing that God doesn't exist.
 Neo-Aristotelians have to accept that everything that exists is knowable. For on their hylomorphic ontology everything that exists is either pure form or form realized in matter. Forms are intelligible and constitute the essence of beings. But then all beings are knowable. Aquinas and other medieval philosopers took it that 'true' is a transcendental. Thus 'true' was considered to be co-extensive with 'being'. Hence they held that all beings are true, which only makes sense if understood as the claim that all beings are intelligible.
 Here it is taken that for the actual world's root of reality to exist in that possible world, it must be the root of reality of that world. For a being in a non-actual possible world that is not the root of reality in that world cannot be identical to the actual world's root of reality.