Fundamentalism did not arise out of a single event or in a single generation. The belief system that surrounds "the fundamentals" was born, at least in part, out of an ecclesiology that sought to be obedient to God's Word. The issue and especially the application of ecclesiastical separation were at the heart of the division that occurred between evangelicalism and fundamentalism in the middle of the twentieth century. While much has been written on the histories of these movements, the theological basis of that division has frequently been overlooked. Examine within the pages of The Church of the Fundamentalist how the ecclesiologies of mid-twentieth century fundamentalists and evangelicals affected their views of separation and how those views led individuals to establish, abandon, or modify their application of ecclesiastical separation. The Church of the Fundamentalists explores one theological basis for the division of fundamentalism and the new evangelicals of the mid-twentieth century-the doctrine of the church.