To be an atheist is to maintain God. His existence or his nonexistence, it amounts to much the same, on the plane of proof. Thus proof is a word not often used among the Handdarata, who have chosen not to treat God as a fact, subject either to proof or to belief: and they have broken the circle, and go free.
To learn which questions are unanswerable, and not to answer them: this skill is most needful in times of stress and darkness.
Chapter 11 Soliloquies in Mishnory (p. 151) - Hainish Cycle - The Left Hand of Darkness (1969)