Wikipedia says this: "In traditional logic, an axiom or postulate is a proposition that is not proved or demonstrated but considered to be either self-evident, or subject to necessary decision. Therefore, its truth is taken for granted, and serves as a starting point for deducing and inferring other (theory dependent) truths." I don't understand this part: "... or subject to necessary decision". So, one can "create" an axiom that isn't self-evident? How does that work?