We've got to believe in something 4~attack

 (also referred to as Fragments of Truth #4 ~ Attack) is a track in Xenosaga II to III: A Missing Year. It is a version of we've got to believe in something from the Xenosaga III: Also Sprach Zarathustra Original Sound Best Tracks, along with, , and

It plays when Doctus damages KOS-MOS at the start of Chapter 2 (before the title card).