The mid-nineteenth century is a gold mine for contemporary scholars interested in American Protestant ecclesiology. There one will find the extensive writings of John Nevin who came to the notice of the theological world with The Anxious Bench, a critique of the “quackery” of Protestant revivalism. Influenced by a critical appropriation of cutting-edge contemporary German theology, he came to believe that the church was not “invisible,” but the visible manifestation of Jesus Christ’s incarnate life. Christians were to pursue unity, not in external institutional arrangements, but as unity of spiritual life. This compilation presents his theology of the catholicity of the church prior to his masterwork, The Mystical Presence, and a multifaceted, sophisticated critique of American sectarianism. This edition carefully preserves the original texts while providing extensive introductions, annotations, and bibliography. The Mercersburg Theology Study Series presents for the first time attractive, readable, scholarly modern editions of the key writings of the nineteenth-century movement known as the Mercersburg Theology. An ambitious multi-year project, it aims to make an important contribution to the academic community and to the broader public, who can at last be properly introduced to this unique blend of American and European Reformed and Catholic theology.