The Catholic Beethoven offers a new view of Beethoven and his religious music by demonstrating that both the composer and his sacred works were influenced by the German Catholicism of his era to a greater extent than has been thought. Since the middle of the nineteenth century, most accounts of Beethoven's religious attitudes have assumed that, as a child of the Enlightenment, the composer was estranged from the Catholicism into which he was born, adhering instead to an idiosyncratic and unorthodox religious outlook that was suspicious of dogma and tradition. This assumption has often resulted in the critical marginalization of Beethoven's religious music, with the notable exception of the Missa solemnis, which is usually included among his most important compositions only by being reinterpreted as a humanist or universalist work transcending its superficial identity as a setting of the Catholic Mass. This book argues that such views have relied on an inadequately complex view of the Enlightenment, which presumes incorrectly that the Enlightenment was monolithically opposed to traditional religious belief. Beethoven's religious outlook was primarily shaped by ideas associated with the German Catholic Enlightenment, a particular strand of the Enlightenment that sought to reconcile traditional Catholic beliefs with elements from more familiar, secular versions of the Enlightenment. The book uses the central concerns of this Catholic Enlightenment as a framework for interpreting Beethoven's sacred works-not just the Missa solemnis, but also the Mass in C, Christus am Ölberge, and the Gellert Lieder-as well as documentary evidence usually cited in relation to the composer's religious outlook. In addition, it will situate the content of a number of religious books in his library within the religious-historical context of his time. Particular attention is devoted to Beethoven's interest in the writings of Johann Michael Sailer (1751-1832), one of the most important figures in German Catholicism during Beethoven's time, with whom the composer also had a personal connection.