What is Atheism?

[Neo-Scholastic]

To quote myself from another thread, it seems rather odd when a proposition like "'God exists' is true" can be considered either true or not true because it is a belief, whereas its negation, "'God exists' is not true", cannot be either true or not true because it isn't considered a belief. How can any given proposition, P, be true or not true while it's negation, not-P, cannot be true or not true? How can anyone claiming to be a paragon of logic say the first proposition is a belief but the second is not?

Suppose the proposition in question is "That 'natural selection occurs' is true." Now it either is or it isn't. Does the same hold for the proposition "That 'natural selection occurs' is not true?" Presumably the supporters of evolution, which include me BTW, will present data and observations they believe confirm the proposition. While there will always be a group of people who don't care, those deniers who do will raise objections, i.e. present beliefs about how the data should be interpreted and the observations suggest something else. To the degree that they find the data inconclusive they are justified in saying that the proposition "That 'natural selection occurs' is untrue." If they are going to say the proposition is not true then they have a burden of proof with respect to their objections of the evidence presented.

These debates do not happen in some gnostic vacuum. Any atheist who claims there is insufficient evidence for the existence of God is tacitly admitting that they have reasons to reject the evidence offered and by extension are indeed claiming that the proposition "God exists" is not true.