Johann Adam Mohler was twenty-nine years old and a lecturer at the Catholic seminary in Tubingen 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. Now, with the appearance of its first English translation, Mohler's work will receive the careful study it deserves.