This series is the first modern edition of the main body of Mercersburg theology. It includes all the important works, large and small, of John W. Nevin, Philip Schaff, and lesser Mercersburg figures, covering the significant doctrines and issues of the movement. Each volume includes critical or explanatory notes, relevant introductions, and bibliographies of modern works. With few exceptions, the early texts are reproduced in unabridged form. Since the original Mercersburg materials are now extremely scarce, and almost impossible to assemble in their entirety, the Lancaster Series forms an invaluable resource for historians of American Christianity and, in particular, for serious students of theology. It will commend itself to all those who wish to understand the nineteenth-century background of contemporary Protestantism. Both of the Mercersburg theologians, Schaff and Nevin, looked forward to a new age of the church - an age which would call into unity and catholicity all the divisions of the body of Christ. Philip Schaff (1819-1893), American theologian and church historian, was born in Chur, Switzerland on the fist of January, 1819. He was educated at the gymnasium of Stuttgart, and at the universities of Tuebingen, Halle, and Berlin, where he was successively influenced by Baur, Tholuck, and Neander. In 1843 he became Professor of Church History and Biblical Literature at the German Reformed Theological Seminary of Mercersburg, Pennsylvania. His inaugural address on The Principle of Protestantism, delivered in German at Reading, Pennsylvania, in 1844, and published in German with an English version by J. W. Nevin, was a pioneer work in the field of symbolics. Sam Hamstra Jr. is the Affiliate Professor of Church History and Worship at Northern Seminary. He is the editor of several studies, most recently The Reformed Pastor: Lectures on Pastoral Theology by John Williamson Nevin, and has authored several works on worship, including What's Love Got to Do With It? How the Heart of God Shapes Worship . John Williamson Nevin (1803-1886), professor successively at Western Theological Seminary, the Theological Seminary of the German Reformed Church at Mercersburg, and Franklin and Marshall College. He was a leading nineteenth-century theologian and founding editor of Mercersburg Review . Bard Thompson (1925-1987) received a PhD at Union Theological Seminary in 1952. Before coming to Lancaster Seminary in 1961 he served on the faculties of Candler School of Theology and the Divinity School of Vanderbilt University. He is the author of Liturgies of the Western Church (1961) and co-author with Howard Paine of Book of Prayers for Church and Home (1962). His lecture The Heidelberg Catechism and the Mercersburg Theology constituted his inaugural address as professor of church history at Lancaster Theological Seminary. The two other Thompson essays were given at Mission House Theological Seminary in June 1961 as part of the celebration of the centennial of that seminary.