During the 19th century the German Reformed Church debated issues such as revivalism and especially the Mercersburg Theology of John Nevin and Philip Schaff. In 1866 Samuel Miller, a member of the German Reformed Church, published a work entitled "A Treatise on Mercersburg Theology: Mercersburg and Modern Theology Compared". Other controversies, such as debates over liturgy, also occurred in the 19th century. In the second half of the century, the congregations formed their first General Synod, held in 1863. In the 1870s and 1880s, there were attempts, albeit unsuccessful, to unite with the related and Calvinist Dutch Reformed Church.