Dr. John Gerstner was a professor of church history at Pittsburgh Theological Seminary and an expert on Reformed theology, especially the works of Jonathan Edwards. He was also a dear friend and mentor to Dr. R.C. Sproul.

Dr. Gerstner went on to teach theology, philosophy, and apologetics at the Ligonier Valley Study Center founded by Dr. Sproul. He wrote many books, including Primitive Theology, a collection of primers on fundamental biblical doctrines. In addition, he recorded several video teaching series with Ligonier Ministries, including a one-hundred-message overview of systematic theology. Known as an ardent defender of Christian orthodoxy, Dr. Gerstner also served on the International Council on Biblical Inerrancy.