Quote Originally Posted by Aurons Ghost

Ok, so did the fayth gather before Sins arrival, were the people ordered up gagazet and told to become fayth by Yu Yevon before he became sin, or were the populace manipulated into it after sin destroyed Zanarkand, and so leaving only the survivors to become the Fayth?
You can't have Dream Zanarkand or Sin if there is no fayth to begin with.

Cause the fayth is needed to summon Dream Zanarkand and after that, Yu Yevon gather pyrefiles with gravity spells and created Sin to protect him and Dream Zanarkand.

So all of them become fayth before Sin came about.