Johann Adam Mhler was twenty-nine years old and a lecturer at the Catholic seminary in Tbingen when he wrote Die Einheit in der Kirche (Unity in the Church) in 1825. Its two German editions and French translations influenced Catholic authors well into the twentieth century, and the book remains an important example of the early-nineteenth-century Catholic Awakening.In Unity in the Church, Mhler upholds a romantic view of the Catholic Church by describing it as the organic development of the life-giving Holy Spirit. This, he insisted, was the teaching of the earliest Christian writers, whom he discusses and quotes at length throughout the book. Although Mhler was primarily writing as an apologist for the Catholic faith against Protestantism, his work is marked by careful study of Protestant sources, respect for Protestant thought and thinkers, and a reconciliatory tone.In this book he uses the works of the church fathers to demonstrate to his contemporary Protestant opponents that the Scriptures arose from within the church and that the earliest heresies resulted as individuals separated themselves from tradition, which has as its life source the Spirit. The Spirit works through tradition as the source of the church's mystical and intellectual unity, a unity which allowed for diversity, but which over time formed itself under bishops. According to Mhler, the principle of unity in the church must continue until it reaches its fullest form; thus, the unity of the episcopate and all believers must represent itself in one church and one bishop. A single bishop, the primate, is the center of the living unity of the whole church.This translation is aimed at individuals interested in the development of Catholicism in the modern world and in Catholic-Protestant dialogue and ecumenism generally. It is also an important work for historians and theologians specializing in Catholic historiography, the Scripture-tradition relationship, issues of church and state, and Catholic liberalism.