Many early modern Italian nobles were obsessed with duelling. Despite bans from secular authorities and the Council of Trent, the violent honor complex was veiled in part under the title of the scienza cavalleresca, the knightly science, which provided rules for the conduct of conflicts between aristocrats and those with noble aspirations. Such rules were both concerned with emotions and the object of emotions. Using the tools of the history and sociology of emotions, this article contributes to the emotional history of the scienza cavalleresca through examining the rules proposed both as feeling rules in themselves and as objects of emotional judgment. Toward the turn of the eighteenth century, more aristocrats began rejecting such codes with explicit objections to the scienza cavalleresca and its ethical basis. One such noble was Paolo Mattia Doria (1667–1746), a notorious duellist in the closing years of the Spanish regime, who renounced the vendetta and expressed disgust with its practitioners. A zealous convert against the noble vengeance system, he will serve as an example to explore the wider struggle over emotional values in early modern Italy and, more generally, in societies with high levels of violence. The article traces the role of emotions in the scienza cavalleresca, the taste for dispute through one genre (letters of challenge or cartelli di sfida), then explores the case of Doria. From these three stages, the article argues for the significance of adopting approaches from the sociology of emotions to analyze elite cultures of violence.