What does it mean to say that "God is within us?" For some, this could simply be the very fact of consciousness, which for others is just "what the brain does." And the corollary question, of course, is if God is "within us," does this God die when we do?

The interesting thing about your question, "which God are atheists trying to disprove," is not one that I would have thought of. Atheists will tell you that you cannot prove or disprove God, and that it is pointless trying.

All of the "proofs" that have been tried with respect to God have been by theists, those like Anselm, and others, who have created the Ontological Argument, the Anthropic Argument, the Cosmological Argument, etc., all of which are supposed to prove the existence of God. Atheists don't offer up a proof of the non-existence of God, they merely show how those particular arguments fail to make the case for God.

But I will agree that all of those arguments are predicated upon a God that is somehow a separate entity. Once we begin to argue that "we are god and god are we and we're all us together" (as the Beatles might have sung it), well those arguments go out the window, but then you need to resolve what you mean when you say things like "God is within us."

Now, my suspicion (and it is just a guess on my part, informed by zero wisdom) is that what people mean when they say that "God is within us" is that there is something special about human beings, which does not pertain to any other species on earth -- something that sets us apart, that might be called "divine." But the real question, the one that is still left open, is whether or not that something special can exist without the shell in which it currently manifests itself.

And once again, I think you'll find that such an idea can neither be proved nor disproved, and we're all back to believing or not believing on what we perceive to be the balance of evidence.

__________________
evangelicalhumanist: Greek "eu"=good and "angelos"=messenger. Spreading the good news of Humanism.