William Edgar (DTheol, University of Geneva) is professor of apologetics and John Boyer Chair of Evangelism and Culture at Westminster Theological Seminary. William lives in Philadelphia, Pennsylvania, with his wife, Barbara. They have two children and three grandchildren. Stephen J. Nichols (PhD, Westminster Theological Seminary) serves as the president of Reformation Bible College and chief academic officer of Ligonier Ministries. He is an editor of the Theologians on the Christian Life series and also hosts the weekly podcast 5 Minutes in Church History. Justin Taylor (PhD, The Southern Baptist Theological Seminary) is the executive vice president of book publishing and book publisher at Crossway. He has edited and contributed to several books including A God-Entranced Vision of All Things and Reclaiming the Center, and he blogs at Between Two Worlds-hosted by the Gospel Coalition.