What if Tyler Durden was the "real" one? What if this was an utterly insane person, who, at some point in life, developed a "normal" alter-ego, that then completely overtook him? (let's call the "normal" one "Jack". Yes, I know it's not his actual name, but whatever, everyone calls him Jack anyway") My reasoning: We know the name of Tyler Durden, but we don't know anything about Jack.