On a more or less standard Christian understanding of the world, God is the creator of everything that exists, other than himself. This creation is often described as "ex nihilo," in the sense that when God creates the world he does not make use of any materials which exist prior to his creation. Call this the doctrine of creation.
The doctrine of creation tells us that God's creative activity is intentional, and the traditional way to understand the intentionality of God's creative activity is to say that God has an idea of the world prior to his creation of the world.
On this view, a good answer to the question, why is there the very world there is? is that God had an idea of this world, wanted to create it, intended to create it, so created it. I just made a patio. Prior to making the patio I formed an idea of what I wanted to make. Then my making was an attempt on my part to realize that idea in actual soil and stone. That's a little like how God creates the world intentionally.
Lately I've been reading and thinking about what sort of explanation might be offered for the fact of God's having the very ideas he has. Lots of views have been offered over the years, but the one which attracts me most is the one which held sway over the minds of Christians from Augustine to Aquinas.
It goes like this: God perfectly understands himself and this self-understanding may be thought of as an idea which perfectly represents God. It follows from something's being a perfect self-representation that it perfectly represents the whole of oneself along with all parts and properties of oneself. Call a representation of one or more (but not all) parts or properties of oneself, a "partial self-understanding." God's partial self-understandings turn out, on this venerable view, to be his ideas of creaturely natures.
So on this view, a divine idea of some creaturely nature is just included within God's total self-understanding. We might say that there IS nothing that is non-divine about a creaturely nature. All there IS to it is divinity; but it is not the WHOLE of divinity, so it is not itself divine.
Is the venerable view cogent?
I have my doubts.
If God is simple then he has no properties or parts to slice off; all of God is all the same. So God cannot have a partial self-understanding.
You might say, well, since God is omniscient then God knows how finite intellects would think about God, if there were any. And finite intellects like ours would not be able to comprehend God in his simplicity; we would mentally divvy up God into his various attributes, as we do. God knows this. So God has ideas of how finite intellects would think of him.
The problem here is that we're trying to explain how God gets his ideas of creatures from his own self-understanding. But an idea of a finite intellect is an idea of a creature. So it is one of the ideas which needs explaining, and it cannot explain itself.
Suppose you're not concerned about that problem; here's another one. Among all the properties we know about, some are worthy candidates to be be divine attributes and some clearly are not. For example, being wise or just or powerful turn out to be divine attributes on a traditional understanding of the divine nature, while being shaggy or sticky or noisy do not. God has ideas of all these properties, both the ones he is and the one he is not. Plausibly, he gets ideas of the ones he is from understanding himself; but it's hard to see how he gets the ones he is not in this way.
But on the venerable view, God is supposed to get ALL his ideas from his idea of himself. How can he get ideas of the things he is not from his idea of himself? I'm not sure.
I'm very attracted to this venerable view since it's very simple and tidy and beautiful and highly honorific to God. I'm working on details of it. Not sure if it'll work out. If it doesn't, I may be forced back to this other beautiful view I was working on for a while. That wouldn't be so bad.