What is the only way to demonstrate one's faith in the God's complete power over the fate and destiny of humans? Under what conditions is it permitted to let a non-Jew die, or to kill unarmed civilians in warfare? These are the kinds of questions asked and answered by the theologians and ideologues of the more radical forms of Islam and Judaism. But the reasoning by which the answers are found, and the assumptions about human nature that determine the answers, say more about the individuals...