Why couldn't the world that concerns us- be a fiction? And if somebody asked, 'but to be a fiction there surely belongs an author?'- couldn't one answer simply: 'Why? Doesn't this "belongs" perhaps belong to the fiction, too?'
Truth is more of a stranger than fiction. When in doubt, tell the truth. If you tell the truth, you don't have to remember anything. Most writers regard the truth as their most valuable possession, and therefore are economical in its use.