Originally a political and theological liberal, he turned to the patristic writings in the early 1970s under the influence of a Jewish colleague, Will Herberg, and discovered what he described as "ecumenical orthodoxy", the interpretation of the New Testament and apostolic doctrine which is universal and accepted. As he wrote in the preface of his "Systematic Theology": "My basic goal is to present an orderly view of the faith of the Christian community, on which there has generally been a substantial agreement between the traditions of the East and the West, including Catholicism, Protestantism and Orthodoxy."