0.) Consider the idea that God is that than which nothing greater can be thought, but the think of the greater as being in logical universality, the way “animal” is greater than “dog” and “living” is greater than “animal”.
1.) This can be taken either to mean that God is the most general genus, or that we are unable to capture or locate God in any genus. The first is a claim about God’s existence, the second about our knowledge. The first is substantially false but with a suggestion of the truth; the second is a cornerstone of St. Thomas’s apophatic theology.
2a.) The first is crazy so far as no one intends to call something God when he calls it real – the question whether Narnia exists is not a theological inquiry. The element of truth is that being is a point of contact between God and the universe, and like all points of contact it can be considered either in relation to what came before, and so is God himself, or according to what came after, and so is creation. This is why being is not just the most general concept we can think of but is also the most formal. In the first sense it is the vaguest of vague things, in the second it is the perfection of all perfections.
2b.) And what do we have to say to Quine or Kant, who would see being as a relatively uninteresting logical concept? I’ll do them one better and argue that, so far as we try to capture being in a formal system, the concept is not just uninteresting but impossible. Lo, I am more a Positivist than any Positivist, more extreme in denial of metaphysics than any of its critics. How?
3.) Logical universals might be taken either as genera or as effects of some universal cause (like art might be taken either as a genus of things or as an effect of the human mind; or the way life might be a genus or that which is ultimately explained by a complete biology). In this sense, only “being” puts us in immediate contact with God. If we consider “life” we explain it not just in relation to divine action but also secondary causes. But if we insist that being fall into some formal system, the concept is impossible (Russell’s paradox, Gödel, the halting problem, etc.). Since this arises from problems of self-reference, being cannot be seen totally as an object but also as a self-intuition. “Being” must be present to a self that is present to itself. The human mind cannot achieve this perfectly, because for us it is a different to think of something and to use it in an act of self-recognition. Only a mind with no division or incompletion in its cognitive act could have a concept of being simpliciter. Thus if being is intelligible, God exists; and if we dwell on the imperfection of our knowledge, metaphysics is impossible. Our notion of being, as St. Thomas says, must be borrowed from God if we are to have it at all.
4.) And yet we cannot start with some general idea and winnow it down until we describe God. We can only do this in things because of the difference between what they are and their reality, but there is no such division in God. If we could define him, we would need no additional information to know he really existed. But our power to define cannot do this. Either “God” self-evidently exists, or we have no non-divine self-evident concepts in light of which we might describe him. ;Both seem false.
5.) And yet causality or cause is not a general class. Causes within a genus are not causes formally. Thomistic apophatism is thus compatible with drawing causal inferences from the world to God; and the subsequent description of God as a sort of cause is not a way of locating him in a genus.