Roma Sempiternal: Porphyry and the Imperialization of the Papacy in Medieval Rome

Abstract

This dissertation explores the role of porphyry in the imperialization of the papacy that took place in Rome between the fourth and twelfth centuries. Porphyry is a purple marble that was quarried in Egypt between approximately the first and fifth century CE. Originally imported to Rome where it was the exclusive prerogative of the emperor, porphyry was later used and reused by rulers throughout the Italian peninsula and wider Mediterranean. This study argues that porphyry was an inherently Roman material, whose symbolism was derived and produced by its inheritance through the chain of rulers of sempiternal Rome. Before the marble was Christianized under Constantine in the fourth century, it was associated with the Roman emperor who also carried the title of Pontifex Maximus (“greatest priest”). From the time of its discovery and its earliest uses by first century emperors, porphyry carried a religious and political significance that was necessarily tied to the concept of Roman imperium because, like the Roman emperor, it bridged the worldly and the divine. Following the Christianization and gradual dissolution of the Western Roman Empire, the marble fell into the hands of the pope who – as the new Pontifex Maximus – was bishop of Rome and successor to the see of St. Peter. No longer the right of the emperor alone, from 312 onwards porphyry was the inheritance of both the secular and religious rulers of Rome. This project traces the use of porphyry from its discovery by Roman legionaries to its use by the medieval papacy and its rivals, ultimately arguing that the status and symbolism of porphyry were fundamentally linked to the sempiternity of the Roman Empire, which was the notion that “Rome” would persist in successive iterations until the end of time. This study addresses the dual religious and political significance and Roman inheritance of porphyry across four chapters. Chapter 1 is an introduction to porphyry as both a material and symbol of the Roman Empire. The chapter outlines the geological properties of the marble and considers its treatment by historical sources. After detailing the origins of the color purple as a symbol of royalty and imperium, the chapter ends with an explanation of the theoretical framework of the study. Chapter 2 aims to establish that porphyry was a specifically Roman rather than Hellenistic material. A reappraisal of the textual and material sources demonstrates that speculation as to whether porphyry was carved or valued in Ptolemaic Alexandria is historically unfounded. Chapter 3 details the use of porphyry in Imperial Rome, and its Christianization under Constantine. By foregrounding the funerary use of porphyry, it is argued that the porphyry sarcophagus was an analogue for the body of the Roman emperor. An examination of passages from the fifth-century Passio sanctorum quatuor coronatorum from a new perspective finds that the hagiography portrayed porphyry as a uniquely Christian material. In closing, Chapter 4 considers the presence of porphyry in Roman ecclesiastical spaces and its use by the medieval papacy. Beginning with the history of the Vatican rota porphryretica, the significance of porphyry rotae (pavement roundels) is explored within the context of polychrome cosmatesque pavements and papal ceremonial. The ninth and twelfth century phases of medieval papal patronage of porphyry are placed into dialogue with the propagandistic texts, the Actus Silvestri and Donation of Constantine, and tensions between the papacy, Carolingians, and Normans. From its early usage as a material signifier of the divinized Roman emperor, to its programmatic use in twelfth-century papal patronage, porphyry physically embodied and represented the dual religious and political authority of the Roman ruler, evoking for its audience the genealogy, power, and splendor of the Roman imperium.