Ornato e decoro: a produção teórica de Giovanni Battista Piranesi e os debates arquitetônicos setecentistas

This article aims to analyze how the architect and engraver Giovanni Battista Piranesi formulated the concepts of ornament and decorum in his theoretical production of the 1760s. To this end, the study examines his work Parere su l’architettura in dialogue with other writings, identifying the strategies used to present his position in relation to contemporary theorists and to intervene in the eighteenth-century architectural debate. The analysis seeks to reveal the rhetorical articulations in the way he formulates his arguments according to the purpose of each publication. Piranesi draws on a broad repertoire that includes ancient authors (Vitruvius, Cicero, Horace, and Pliny) as well as contemporary ones (Lodoli, Memmo, Algarotti, Mariette, and Laugier). The conclusions indicate that, for Piranesi, ornament constitutes an integral part of architecture when subordinated to decorum, understood as the suitability between function and formal unity. Finally, it is demonstrated that the value of the debate lies in the way Piranesi reaffirms the relevance of invention, defending ornament as a crucial element for the expression of genius. From this perspective, the aim is to contribute to understanding the relevance of Piranesi as an interlocutor on the complex role of ornament and decorum in the historiography of architecture.