Why do Athiests require 'proof' that God exists?

[Tea Earl Grey Hot]

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Why does it seem to you that only in God one can have an absolute standard of truth from which logic reflects? What does God provide that the universe by itself doesn't, in other words?

The metaphysically necessary preconditions for the existence and intelligibility of normative and necessarily true propositions.

I can't deal with all your points just yet because this is an area I haven't properly studied.

It seems to me that whether or not God exists, a person's understanding of rationality ultimately comes from universe. For instance, I can hold a red ball in my left hand and a blue ball in my right hand. I can see that they're two different objects. The blue ball cannot be the red ball. I can try to mash them together has hard as I can and they are still separate entities. But nevertheless the red ball is still itself, and the blue ball is still itself. Perhaps this is ultimately where the law of non-contradiction comes from. It's inconceivable for the red ball to be the blue ball because I have no experience of this being possible.

One might say logical laws are the result of analogous experiences that we have everyday of our lives since childhood. If you were to ask me how I know that A cannot be not-A, I might say because I have no experience nor conception otherwise.

Also, I don't see how positing the existence of God helps in this matter. If all our knowledge comes from experiences and memory of the space/time universe, and God is immaterial/eternal perhaps he could have created a universe made up of something other than space/time, and we'd then have completely different "logical" laws.