PIETRO, DIACONO, saint. - A Roman deacon in the time of s. Gregorio Magno, he died in 606. Still young, after distributing his entire patrimony to the poor, he withdrew to the monastery of S. Andrea on the Caelian Hill in Rome, where he lived together with s. Gregorio.
He was administrator of the goods of the Church, first in Sicily and then in Campania, as is shown by numerous letters addressed to him in those places by s. Gregorio himself. Subsequently he was made cardinal deacon and lived at the court, becoming the Pope’s confidant, who also made him the interlocutor in his Dialoghi. His fidelity to s. Gregorio was revealed above all at the death of the great Pope, whom he defended against unjust attacks; but the account of the affair given by Giovanni Diacono in the Vita di Gregorio is legendary. His cult dates from time immemorial. Some scholars do not identify him with the steward of papal goods, and consider him a cleric rather than a monk.
PIETRO, DIACONO. - Librarian and archivist of the abbey of Montecassino, born c. 1107, died in 1159. Under the guidance of the monk Guido, P. acquired a solid erudition in sacred sciences and history. Perhaps due to his restless spirit, he was away from Montecassino for some time; but upon returning to his abbey, at the behest of Abbot Senioretto and even more out of an inner literary passion, he devoted himself with surprising alacrity to composing various works of hagiographic and historical character, not without occasionally altering oral and documented tradition to suit his purposes.
Among these, the continuation of the Chronicon Casinense by Leone Ostiense is remembered, in which he also utilized the work of his teacher Guido while simultaneously introducing modifications not always felicitous to Leone’s work. His other published works include: Liber illustrium virorum archisterii Casinensis; De ortu et obitu iustorum Casinensium; Liber de locis sanctis; PL 173. Therein is also the portion he wrote of the aforementioned Chronicon Casinense, reproduced in Wattenbach’s edition in MGH, Script., VII, p. 551. Other writings remain unpublished in Cassinese codices; among these, the Registrum is worthy of mention, in which P. collected abundant archival material to defend the patrimonial rights of his monastery. He himself recounts the defense of these rights before Emperor Lotario, who decided the dispute in favor of Montecassino.