The question comes up, is a person what they call themselves, or what their statements reveal them to be? Peart's claim that he was an "agnostic" is 30 years out of date. Whatever he chooses to call himself, he stated unequivocally in Ghost Rider, a 2002 memoir, that he does not believe in God. That moves him to atheist category, whether he likes it there or not. I no longer have the book, so I can't give a direct quote.