Authors: John Williamson Nevin (1803-1886) was an innovative and controversial American theologian. Although reared in Presbyterianism, Nevin became the premier exponent of the "Mercersburg Theology" of the German Reformed Church. He promoted a view of Christianity as evolving, focused on the Incarnation, and centered in the sacraments. Philip Schaff (1819-1893) was a German emigr� who taught theology and church history at Mercersburg Seminary and Union Theological Seminary, New York. In the United States he pioneered the study of the history of Christianity and was a progenitor of the ecumenical movement. John Williams Proudfit (1803-1870) was a classicist and ecclesial historian who taught at New York University and New Brunswick Seminary. His more bibiliocentric Reformed theology motivated him to passionately and caustically critique Nevin's work. Editors: Charles Yrigoyen Jr., a prominent pastor, teacher, and scholar, has written numerous books and articles on the history of Methodism and on the Mercersburg Theology. He has coedited two volumes of the highlights of the Mercersburg Theology: Catholic and Reformed: Selected Theological Writings of John Williamson Nevin, and Reformed and Catholic: Selected Theological Writings of Philip Schaff. Lee C. Barrett is a professor of theology at Lancaster Theological Seminary. He has authored several books and articles interpreting the writings of S�ren Kierkegaard and is a coeditor of the Mercersburg Theology Study Series.