Jen has a good post up about a recent visit to Adoration in which she felt little but nevertheless took away great insight. That's the main thrust of her post and is a good reason to go read it. I was struck by a particular point she made, a side point:
I've been brought to a place where I no longer even think of it in terms of whether or not God exists -- "exists" being a weak word with an obvious antonym, implying that nonexistence is possible. To say that something "exists" usually has the unspoken implication of a transitory state, since every material thing in the universe will eventually cease to exist. Duck-billed platypuses exist; spiral galaxies exist; I exist. The English language doesn't have a proper word to describe the state of being of God, who always was and always will be, who is more real than reality, other than to simply say that God is.
English - perhaps all languages, I don't know - is a bit impoverished when it comes to the words "exist" and "existence." We apply them to the unique kind of existence possessed by God, who alone exists in and of Himself; and we also apply them to what material objects are doing for as long as they last. Really the two kinds of existence are so very different that they ought not to have the same term apply to them.
Lacking a concise way to distinguish between them can lead people into logical fallacies. For example, "the universe" is sometimes defined as "the set of all that exists." Not a good definition, if you also hold that God "exists" *and* that God is not a member of the set defined as the universe, but is rather its creator and logically not part of a set. This will get you into trouble with atheist pedants who can then counter that the contradiction is yours, since if God is not a member of the set of "all that exists," then God must not exist. Always remember to define your terms! If the universe is defined as "all that exists," then God has to be said to do something other than exist. Transcend existence, maybe, or pre-exist.