Ironically, in each case the individual's testimony is consistent with his experience; for one the existence of God is proven fact, but for the other there is no experiential evidence, and the best perspective such a one can muster on such a basis is agnosticism.
As a Christian I have no beef with the agnostic on that basis, though we may disagree on other points. However, I do have rather a bone to pick with the atheist who generalizes from his own absence of evidence a universal evidence of God's absence.
First the existence of God is not a proven fact. Secondarily, Heisenberg's uncertainty principle proves that an Omniscient God cannot exist, because it is impossible to know both the position and momentum of a particle at the same time.
Atheism is the wrong term. Do you call someone who doesn't believe in Santa Claus an anticlaus? The burden of proof is on those who believe in Santa Claus to prove that he exists.
I agree. Atheism seems to be a logical fallacy, an argument from silence, or poor abductive reasoning (what of the order in the universe, and the fact that the first mover must be outside of time and so supernatural?). Agnosticism is a more intellectually and personally defensible view.
Atheists don’t view the existence of God as proven fact— just that it’s so improbable, so unknowable, so unprovable, that it’s not at all worth considering. It’s not provable either way, which is the point. If it’s not provable, the default position is “unproven.” No proof of unicorns and they are improbable, therefore it’s unproven and not worth serious consideration.