Stephen Um (PhD, University of St. Andrews) is senior minister of Citylife Church in Boston, Massachusetts, and president of the Center for Gospel Culture. He serves on the board of directors for the Gospel Coalition, is an adjunct faculty member at a number of theological seminaries, and is an associate training director for Redeemer City to City Asia. He is the author of several books and articles and the coauthor of Why Cities Matter.
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 president of the Gospel Coalition, and has written or edited nearly 60 books including Scandalous, Memoirs of an Ordinary Pastor, and The Difficult Doctrine of the Love of God. 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.