When considering the “what” or the substance of God, we must admit that we cannot know it. We get things wrong if we think God is something we can picture or get our minds around. St. Anselm says, “I would be surprised if we could find anything from among the nouns and verbs which we apply to created things from nothing that could worthily be said of the substance that created all.” We can certainly compare God to things that we know, but these words don’t typically mean the same things as they do when applied to created things. We must realize the words have an analogous relationship.
For instance, I can say that a cheeseburger is good and that Fred is good. The word good does truly and literally describe both Fred and the cheeseburger, but the word has a different meaning when applied Fred than it does when applied to the cheeseburger. In the same way, I can say that God is good and that Fred is good, and that “good” truly and literally describes both of them but does not mean the same thing.
And let’s not forget, we really do have some descriptive words that can be attributed to God, words like Creator, the Source of everything, pure actuality, pure existence, true, good, one, being, real, and beauty. But, unlike us, God does not have these things, God IS these things. And each descriptive word is referencing one thing, not many. It’s like when the words “Superman” and “Clark Kent” refer to the same person. They just refer to him in different aspects. And words like good and true are different aspects of God.
All these things describe the “what” of God. I have not yet gotten to the “who” of God. “What is God” and “Who is God” are two different questions, and not very many people realize that.
The “Who” of God would be hard to figure out on our own but it is possible. For instance, if we consider love to be what God is, as when we say “God is love”, then of necessity we must say that God is a Trinity of “Who’s”. Because, if God is only one “who” then, when considering God before he created anything, what sense does it make to say that God was loving? What was he loving before creation? If God is one “who”, then there was nothing to love. He could love himself, but he would not know the kind of adult, mature love we speak of when we talk about loving another person, when we talk about giving ourselves wholly to them. He would have to create something in order to love, which would mean that he was deficient before creation. Generally, people don’t think “deficient” appropriately describes God.
But, if God is three “Who’s”, then it’s easy to see that he did have this adult love all along. For each “Who” of the Trinity was loving and giving to each other equally before creation. And we are invited into the love that’s already going on, sort of like joining in on a quiet fireside chat.
As you can see, there are some things to be said about God. But we must be careful about the kind of things we say. Attributing created qualities to God as if they were a direct comparison is wrong.