COLIN S. SMITH is the senior pastor of The Orchard Evangelical Free Church in Arlington Heights, IL, where he has been since 1996. He is the author of The 10 Greatest Struggles of Your Life and can be heard on his Unlocking the Bible broadcast with Moody radio. D. A. Carson (PhD, Cambridge University) is research professor of New Testament at Trinity Evangelical Divinity School, where he has taught since 1978. He is a cofounder of the Gospel Coalition and has written or edited nearly 120 books. He and his wife, Joy, have two children and live in the north suburbs of Chicago. TIMOTHY KELLER is founder and pastor of Redeemer Presbyterian Church in New York. He is the best-selling author of The Prodigal God and The Reason for God.