John Duff, Ph.D.

Professor of Historical and Systematic Theology

Faculty Positions:

Traditional Undergrad Academics - Bible, Religion & Ministry

Contact John Duff, Ph.D.

Contact Infox

Phone: 616-222-1202


Everyone is a theologian. Dr. Duff knows this because every semester he teach dozens of students who, though having had no previous class in theology, arrive with very distinct beliefs about God—beliefs about who God is, what God has done in the past and what God is doing now. Often these beliefs lack clarity and precision; nevertheless, these beliefs are firmly held and provide direction for students in the ebb and flow of their lives. These students are indeed theologians, holding a vast array of beliefs about God and the world.

Although every student is already a theologian, it is his hope that they will become better ones. It is Dr. Duff's privilege to help students to examine what they belief and how those beliefs shape their thoughts and action. Since improvement as a theologian is at least partially an intellectual exercise, Dr. Duff and his students work diligently to ground Christian beliefs in God's written revelation—the Bible, to state them as accurately as they can, to eliminate incoherent or contradictory beliefs and to understand why there is some diversity of beliefs among Christians about some issues. These tasks can be arduous, unsettling, and sometimes perplexing; they also can be simple, affirming and clarifying. But they are important tasks to undertake, because the most important thoughts a person can ever have are thoughts about God.

Yet improvement as a theologian is more than an intellectual exercise; it is a moral exercise as well. Christian theology was never intended to merely help students think well but also to live well. Theological study should never become an intellectual club that is wielded in order to win arguments; it should be food that nourishes the soul so that we may grow in faith, hope and love. As Christian believers, we are to grow in grace and in the knowledge of our Lord and Savior, Jesus Christ.

Prior to arriving at Cornerstone, Dr. Duff spent 10 years in church ministry serving as a worship leader and a teaching pastor.

"At CU, I get the privilege of discipling my students by the very nature of the content I teach—biblical doctrine. Something we discuss in class or I have them read has the potential to shape their concept of God and His work in their lives for years. There is nothing that brings me greater joy than to receive that 'out of the blue' phone call or email from an alumnus who expresses appreciation and gratitude for some of the content we covered because it has sustained them in a particular life situation. These reports are both very humbling and very gratifying. Cornerstone encourages teaching-as-discipling and that's a model I heartily affirm."


  • Ph.D., Calvin Theological Seminary
  • M.T.S., Grand Rapids Theological Seminary
  • M.A., Western Kentucky University
  • B.A., Cedarville University


—Reading biographies


—Systematic and historical theology with a special emphasis on eschatology of the 17th Century
—Apologetics and religious epistemology
—History of exegesis