The Prophet of Truth is depicted as a highly religious individual. During Halo 2 he captured 343 Guilty Spark, who told him how to activate the Halo rings. But I have no doubt that Spark would also have told him what they actually do. Truth would have seen him as a representative of their gods, and must have listened; failing that, he could have picked up on a million other clues that would have told him Halo's true purpose. Yet he still continues to try to activate the rings, surely knowing he would die.
Is there anything that indicates if he knew that, and if so, why he continued with his suicidal campaign?