Tidus

"And if we can't think of a way...We'll find another way!"

Explaination

Why does Tidus know nothing of Spira when Zanarkand is a part of Spira?
Well, as found out later in the game, Tidus is nothing but a dream that the faythes created...but then that means the Zanarkand Tidus is from is also a dream. But, the fayths never dreamt of Spira or the war between Bevelle and Zanarkand, only Zanarkand 1000 years ago. Simple, right?