You're hard as a rock... I didn't explain the non-human thing because i figured people were smart enough to understand it. Vivi wasn't human and questioned his existance... He didn't believe he existed in the world because he wasn't normal, and all the other black mages were robot-like. It helps the theme of life to have varying within life. If Zidane was normal, well, that would through the theme of life out the window... The central idea is that everyone exists for a reason, and it brought up questions throughout the game about the central message, which revolves around Vivi. I take it you haven't played all the way through the game. The non-human characters were essential to establish the feelings of isolation and insecurity (Not all of them though.) Some of the non-human characters were also added for comic relief such as Quina. I don't know about you but i knew all of the characters front to back when i finished the game, unlike in 8, which was good nonetheless.