John Anthony McGuckin held the Nielsen Chair in Late Antique Christian History at Union Theological Seminary and was professor of Byzantine Christian Studies at Columbia University in New York City. He is an archpriest of the Romanian Orthodox Church, and rector of the Orthodox Church in Lytham St. Annes, England. He serves on the faculty of church history at Oxford University, and is a fellow of the Royal Historical Society of the United Kingdom. McGuckin has been awarded several honorary doctorates, and has written twenty-five works of historical theology, including St. Cyril of Alexandria: The Christological Controversy, St. Gregory of Nazianzus: An Intellectual Biography, The Westminster Handbook to Patristic Theology, and The Ascent of Law.