Defining "Atheism"

[Ryft]

Those who respond to God-claims with an honest "I don't know" are the indeterminate, not the "non-existent".

"I don't know" is an epistemic response, reflecting agnosticism. The issue is atheism—and, as per Adrian's point, using the principle of excluded middle to argue that there is no third alternative (i.e., if theos is X then atheos is ¬X, which exhausts the category of X.) Agnosticism, as a subset of both atheism and theism, is necessarily a different category (i.e., if gnosis is Y then agnosis is ¬Y, which exhausts the category of Y).