Book excerpt: This book deals with public debate during the Investiture Contest (ca. 1040-1122). During this revolutionary struggle between the secular and the religious powers, polemical writers contributed to the arguably first 'public debate' in medieval Europe. A close reading of a selection of these polemics offers new views on the functioning of the medieval public sphere as well as how the public framework circumscribing the writers led to argumentative innovations. These include an increasing concern with interpretation and contextualisation, resulting in a more critical and probing intellectual community. Public debate during the Contest taught intellectuals how to argue in public and in that respect transferred a lasting legacy to the later Middle Ages and beyond.