English summary: What exactly are people doing when they combat about reforming complex social institutions? How do the advocates and the adversaries of such reforms construct their arguments? How do historical debates on reforms differ from modern ones? The book approaches these questions from the observatory of the late middle ages and the 16th century and is intended to be a contribution to a rhetoric of premodern reform thinking. The setting is the hospital, an institution which was frequently in need of reform, but compact enough to allow detailed description. Four important European hospitals - the Ospedale Maggiore of Milan, the Hotel-Dieu of Paris, the Grosse Spital of Strasbourg, and the Union of hospitals in Modena, Italy offer sufficient source material for an analysis of the verbal (and sometimes physical) strives provoked by the reforms. The protagonists of these debates about words, metaphors, concepts and power were jurists, theologians, political authorities, administrators, religious communities and the lay staff. German description: Was geschieht, wenn uber die Reform komplexer Institutionen gestritten wird? Wie argumentieren die Befurworter und die Gegner solcher Reformen? Unterscheiden sich historische von heutigen Reformdebatten? Das Buch nahert sich diesen Fragen von der Warte des Spatmittelalters und des 16. Jahrhunderts und tragt damit zu einer Rhetorik des vormodernen Reformdenkens bei. Buhne ist das Hospital, eine besonders reformanfallige, aber von der Grosse her uberschaubare Institution. Vier ausgewahlte Hospitaler - in Mailand, Paris, Strassburg und Modena - bieten Material fur eine Analyse der verbalen Kampfe, die Juristen, Theologen, Obrigkeiten, Verwalter, Religiosen und Laienpersonal auf der Suche nach besseren Hospitalern miteinander austrugen.