Norman Geisler's If God, Why Evil? (Bethany House, 2011) lays out in textbook fashion the basic arguments. God is sovereign, so He could eliminate evil by wiping out our freedom to be evil. The existence of evil shows that God values human freedom more than He values the destruction of evil: "Even God cannot totally destroy all evil without destroying freedom. Given that He has willed to create free creatures, it would go against His own will to destroy our free will."
God showed His commitment to free will by forcing Adam and Eve to leave the Garden and enter a world where our desire to embrace evil would give sin even more opportunity. But God's grace shows in His willingness, when we are dead in our sins, to turn our free will into a different channel.
Geisler notes that even we, with our limited understanding, know some good purposes for pain and suffering: For example, pain can keep us from self-destruction (lepers show the horror of not feeling pain), and suffering has to be strong enough to accomplish its warning purpose. Geisler points out that alternatives to a world with suffering-no world at all, or a non-free world where no one sins-are not morally superior.
None of this may satisfy the parent whose child dies. In the end we need to believe that God's infinitely good mind knows the good purpose for everything. The toughest chapter in Christopher Wright's The God I Don't Understand: Reflections on Tough Questions of Faith (Zondervan, 2008) concerns God's command to commit acts against the Canaanites, including their children, that today might be labeled "genocide."
Wright turns down one easy but wrong answer: "It's an Old Testament problem that the New Testament fixes." That doesn't work because it accuses God of encouraging evil in the Old Testament and it doesn't recognize God's mixture of love and wrath in both testaments. Besides, no one in the New Testament suggests that God wasn't speaking in the Old Testament, or had changed.
Wright finds a better answer by placing the Canaan war within the culture and rhetoric of ancient warfare and noting the wickedness of Canaanite society. He then shows that Israel's military ethic was like that of other ancient cultures in one sense but very different in another-because, for Israel, military victory did not mean that Israel was righteous.
Wright also notes that Rahab the Canaanite and Ruth the Moabite were among the foreigners who professed faith in Israel's God and received His blessings. The Jebusites over time may have become a clan of the tribe of Judah, and whole peoples, including even the dreaded Philistines, would one day join God's church as well. God, instead of ordering ethnic cleansing, proclaimed ethnic blessing.
True-and the best answer also emphasizes seeing Christ in the Old Testament. Joshua/Jesus-Yehoshua in Hebrew-means "Yahweh saves." The book of Joshua foreshadows the gospel in many ways. In Chapter 1 the three days of Israelite preparation before entering the Promised Land foreshadow Jesus' time in the tomb. In Chapter 2 the scarlet cord that Rahab tied in her window preserves her to be the ancestor of Christ, who shed His blood for us.
Overall, the book of Joshua shows God pouring out His judgment on a wicked society. The books about the greater Joshua, Jesus, show God pouring out His judgment on His own sinless Son, who did not deserve it.
Stories of perseverance in evil places are both harrowing and inspiring. Primo Levi's classic Survival in Auschwitz is out in a new paperback edition (BN Publishing, 2010). Surviving Hell: A POW's Journey (Encounter, 2011) by Leo Thorsness tells of life in communist captivity. The pilot endured terrible torture but also survived boredom by memorizing long passages of poetry and counting the paces within his tiny cell so he could "walk home" the 10,000 miles from Hanoi.