This is the first English language biography of John A. Mackay (1889-1983), an important Presbyterian leader, missionary, and professor who served as president of Princeton Theological Seminary from 1936 to 1959. As president, he rebuilt the seminary faculty after the split in 1927. His ecumenical vision opened Princeton to a wider ecumenical stance and, under his leadership, the seminary prospered as a leading Protestant theological institution. Mackay was a leading ecumenist for much of the twentieth century and helped establish the World Council of Churches. He also founded "Theology Today" and is recognized as a major figure in both the Presbyterian Church and in theological education.

This biography is made all the more compelling by the fact that it was authored by Mackay's grandson, John Metzger, son of the late Princeton Seminary professor, Dr. Bruce M. Metzger.