About This Word, “Atheist”
I'm sorry, but you're wrong.
For the SEofPh article the main sense of atheism is not a belief, but an affirmation or proposition:
"Therefore, in philosophy at least, atheism should be construed as the proposition that God does not exist (or, more broadly, the proposition that there are no gods).
This definition has the added virtue of making atheism a direct answer to one of the most important metaphysical questions in philosophy of religion, namely, “Is there a God?” "
Agnosticism is not a complement to atheism, but a contrary position:
"But it was Huxley’s application of this principle to theistic and atheistic belief that ultimately had the greatest influence on the meaning of the term. He argued that, since neither of those beliefs is adequately supported by evidence, we ought to suspend judgment on the issue of whether or not there is a God."