Richard B. Gaffin Jr. (ThD, Westminster Theological Seminary) is emeritus professor of biblical and systematic theology at Westminster Theological Seminary in Philadelphia, where he taught for over forty years until his retirement in 2010. He is an ordained minister in the Orthodox Presbyterian Church.

Sinclair B. Ferguson (PhD, University of Aberdeen) is Chancellor’s Professor of Systematic Theology at Reformed Theological Seminary and the former senior minister of the First Presbyterian Church in Columbia, South Carolina. He is the author of several books, including By Grace Alone and Lessons from the Upper Room. Sinclair and his wife, Dorothy, have four grown children.