Whatever God is, the fact that the universe exists proves that God exists.
If only that was so - we wouldn't have 400+ pages in this thread.
We have no evidence of anything that can make the complexity and size of the universe. Whatever could do the making, would fit the general description and definition of God. If it didn't, it wouldn't be able to make something like the universe with all its "furnishings."
''We have no evidence of anything that can make the complexity and size of the universe.'' You are right badecker we don't, why do you claim you do then?
As you say, we don't have evidence of any thing that can make the complexity of the universe. That leaves room for God, only. God, not being a thing, or anything, has made the universe.
What proof do we have for empty space, which is essentially nothing at all? Does it really exist? Yes. We can tell that "nothing" exists by measuring the things that DO exist, and their relationships. In a similar way, even though we cannot directly "lay hands on God" to "measure" Him and prove Him thereby, we can prove He exists by measuring the complexity of the universe, especially with regard to cause and effect.
If we don't have evidence for what can make the universe then we don't. You can't say we don't have evidence for what created the universe therefore god did it, do you not see how that makes no sense? I don't know who created this chair therefore my father did.
It leaves room to anything because we don't know what it was, you don't know if a being aware of himself made the universe or if is just another process that happened because outside our universe there are more universes or whatever, we can hypothesize as much as we want but there is no evidence for any of it.