As I've said before, IMO, FF9 has one of the most important themes of any FF. The entire game is about how one handles ones own mortality. Zidane's carefree and generous way of helping out the lives that need helping shows the importance he places on innocent lives. This rubs off on Vivi who's trying to find out what he thinks of his own mortality. He ends up with the decision of not thinking about when he's going to die, and just make a difference while he can. Kuja decides it's not fair that he dies while everyone else lives (simple logic). Kuja at least had some respect for life, even if he was selfish. Necron is the bitter extreme. He believes that since everything living is simply panting on, suffering, and waiting to die, that by everyone achieving death, the suffering and anxiety that comes along with it will die.