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The Pseudo-Isidorean Decretals (or False Decretals) are a set of extensive and influential medieval forgeries, written by a scholar or group of scholars known as Pseudo-Isidore. The authors, who worked under the pseudonym Isidore Mercator, were probably a group of Frankish clerics writing in the second quarter of the ninth century. They aimed to defend the position of bishops against metropolitans and secular authorities by creating false documents purportedly authored by early popes, together with interpolated conciliar documents.
Historical background 
The turbulent history of the Carolingian Empire during the second quarter of the ninth century sets the stage for the forgers' work. During the early 830s, Emperor Louis I the Pious was deposed by his own sons, only to regain his throne shortly afterwards. Archbishops and bishops had to play an important role in these troubled times. They had to impose penance on the ruler for his allegedly sinful life and thus to prepare his deposition. The excursion in high politics proved disastrous for some of the church dignitaries. In quite summary procedure, they were deprived of their bishoprics and exiled. Thus, ecclesiastical criminal procedure was the forgers' main interest.
The Pseudo-Isidorian Decretals, along with certain fictitious letters ascribed to early popes, from Clement to Gregory the Great, were incorporated in a ninth-century collection of canons purporting to have been made by the pseudonymous Isidore Mercator. Collections of canons were commonly made by adding new matter to old; the forger of the Pseudo-Isidore collection took as the basis of his work a quite genuine collection, Hispana Gallica Augustodunensis, and interpolated his forgeries among the genuine material that supplied credibility by association. The official Liber pontificalis was used as a historical guide and furnished some of the subject matter. The Pseudo-Isidorian collection also includes the earlier (non-Pseudo-Isidorian) forgery, the Donation of Constantine.
Textual overview 
- The addition of forged material to an earlier, entirely authentic Spanish collection containing texts from councils and papal letters originating in the 4th through 8th centuries—the so-called Hispana Gallica Augustodunensis (the name is derived from a manuscript that was at some time in the French city of Autun, Latin Augustodunum).
- A collection of falsified legislation of Frankish rulers allegedly from the sixth to the ninth centuries (Capitularies)—the so-called Capitularia Benedicti Levitae—after the name of the alleged author in the collection's introduction: deacon (Latin levita) Benedictus, as he calls himself. The author falsely states that he has simply completed and updated the well-known collection by abbot Ansegis of Fontanelles (died 833).
- A brief collection on criminal procedure—the so-called Capitula Angilramni—allegedly handed over by Pope Hadrian I to Bishop Angilram of Metz.
- An extensive collection of approximately 100 forged papal letters, most of which were allegedly written by the Roman bishops of the first three centuries. In the preface to the collection, the author of the collection calls himself bishop Isidorus Mercator (hence the name of the whole complex). Besides the forged letters, the collection contains a large amount of genuine (and partly falsified or interpolated) council texts and papal letters from the fourth to the eighth centuries. The genuine and interpolated material derives predominantly from the Hispana Gallica Augustodunensis.
Apart from these four main pieces, there are other minor forgeries derived from the same workshop:
- the so‑called Excerptiones de gestis Chalcedonensis concilii.
- some falsifications in manuscript Hamilton 132 of the Berlin State Library
- the Collectio Danieliana
Much of the work is attributed to "Isidore Mercator", but this is almost certainly a pseudonym created by conflating the names of Isidore of Seville and Marius Mercator, both of whom were well-respected ecclesiastical scholars. The general agreement is that the work had its origin in the Kingdom of the Franks. The forger's main object was to emancipate bishops, not only from the secular power, but also from the influence of archbishops and synods, partly by exalting the papal supremacy.
The author of a rather singular, voluminous section, however, identifies himself as one Benedictus Levita ("Benedict the Levite", or "the Deacon"), and his Capitularia Benedicti Levitae do not deal with early church and papal letters as the rest, but with forged Capitularies on religious and theological matters by various Carolingian rulers, most notably Charlemagne, who take on the role of providing the forger's false authority. It is still under dispute among researchers whether the differently structured and written Capitularia Benedicti Levitae slightly pre-dates and, in fact, originally inspired the authors of the full False Decretals, or whether all the forgeries were fabricated simultaneously.
The overall work probably had the help of several hands but was clearly under the editorial control of a very gifted and, for the day, extraordinarily learned man. While an exact identification of the compilers and forgers is probably impossible, Klaus Zechiel-Eckes has proven that they used manuscripts from the monastic library of Corbie. Zechiel-Eckes has gathered some evidence that an abbot of Corbie, Paschasius Radbertus (abbot 842-847), might be one of those responsible for the forgery. However, it appears safe to assume that the forgers worked in the ecclesiastical province of Reims, and the complex as a whole was more or less completed by 847-852 (the earliest known reference to the text was in 852). It is possible that its composer was ordained illegally by Ebbo, archbishop of Reims, during his brief, but unlawful, reinstatement (840-41).
For approximately 150 to 200 years, the forgeries met with only moderate success. Although a relatively large number of manuscripts dating from the ninth or tenth century is known—altogether about 100 more or less complete manuscripts of the False Decretals dating from the ninth to the 16th century have been preserved—the canonical collections took but little note of the False Decretals until the early 11th century.
During the 11th century, the situation changed rapidly under the impetus of the Gregorian reforms and the Investiture Controversy. Under the impetus of monastic reform movements and the efforts of some Holy Roman Emperors, a group of cardinals and a series of successive popes strove to cleanse the church of abuses and free the papacy from its Imperial patronage, which had recently freed it from the influence of the Roman nobles. The reformers' efforts soon conflicted with temporal power. The bishops of the Holy Roman Empire were crucial to the Emperor's power and were the backbone of his administrative structure. Thus, the emperors were keen to maintain their say on who was promoted bishop and who was not. This intermingling of spiritual and temporal power constituted a deadly sin in most reformers' eyes. After all, St. Peter himself had already condemned the magician Simon Magus (the "Simon" of simony), who tried to buy spiritual power.
Given this situation, the alleged letters from some of the most venerable Roman bishops fabricated by the forgers' workshop came as a godsend. The close interaction of bishops and pope was a welcome proof that the emperors' practice was in blatant contradiction with the oldest traditions of the church. Collections of canon law rediscovered the False Decretals—some were largely extracts from the forgeries. The forgers' intentions, however, were turned around. They had used Rome's power to maintain the independence of the bishops; now the texts were being used to bring the bishops under close scrutiny and to make them dependents of the Bishop of Rome.
This tendency continued to prevail until around 1140, when the learned canonist Gratian published his Concordia discordantium canonum, which increasingly replaced the older collections and was soon regarded as authoritative. Gratian, too, made use of texts from the forgers' arsenal, although, for the most part, probably in indirect ways. With Gratian's work, the immediate influence of the False Decretals had come to an end. As intended, the texts had become an important basis for procedural law, but the outcome was nearly the opposite of what the forgers had intended in the mid-ninth century. The bishops' independence was increasingly restricted by the power of the Church of Rome.
During the Middle Ages, there was little doubt as to the genuineness of the alleged papal letters, but this changed during the fifteenth century. Humanist scholars of Latin, such as Cardinal Nicholas of Cusa, noticed bizarre anachronisms, such as the claim that the martyr-pope Clement I had founded the pre-eminence of certain local churches on the fact that the pagans had their high priests in the same localities. During the sixteenth century, Protestant ecclesiastical historians such as the Centuriatores Magdeburgienses (the Magdeburg Centuriators) criticized the forgeries in a more systematic way, although they did not yet recognize the forgeries as one whole interconnected complex. The final proof was provided by the Calvinist preacher David Blondel, who discovered that the alleged popes from the first centuries quoted extensively from authors of a much later time. In 1628, he published his findings (Pseudoisidorus et Turrianus vapulantes). Some Catholic theologians first tried to defend the genuineness of at least some of the material, but, since the nineteenth century, no serious theologian or historian has denied the falsification.
Efforts to publish the forgeries have been anything but successful. The Hispana Gallica Augustodunensis has not yet been printed at all. There are several editions of the Capitularia Benedicti Levitae, but the last one (Monumenta Germaniae Historica, Leges, folio II, 2, 1831) is more than 170 years old and, from a scholarly point of view, is rather a step backwards compared to the edition by Etienne Baluze published in 1677. The False Decretals and the Capitula Angilramni were printed twice independently. The edition by Paul Hinschius (1863) has sometimes met with unduly harsh criticism, but his choice of manuscripts to form the basis of the edition was rather unfortunate. Moreover, he printed the genuine and interpolated parts of the collection by simply reprinting older versions of Pseudo-Isidore's genuine sources, thus making this part of his edition unusable for critical purposes; for these parts, historians must go back to J. Merlin's edition published in 1525 (based on a single 13th-century manuscript) and reprinted in Migne's Patrologia Latina, Volume 130.
Manuscript tradition 
Seventy-five manuscripts of the Pseudo-Isidorian material have survived, and they differ widely one from another. The manuscript tradition is grouped in at least six or seven classes, which include the following:
Most comprehensive is the one called A1 by Hinschius:
- with Vaticanus latinus Ottobonianus 93 (mid-9th century) as the best representative.
Of equal importance is class A/B:
- The original manuscript of this class was preserved: New Haven, Beinecke Library ms. 442 (written after 858).
- A/B is best represented by Vaticanus latinus 630 (last quarter of the 9th century, from the Corbie scriptorium).
- The so-called Cluny version dates back to the mid-9th century as well.
- Class A2 goes back to the ninth century as well. (Whether the New Haven manuscript or A2 is the better is hard to say.)
- Ivrea Biblioteca Capitolare 83 (9c, Northern Italy)
- and Rome, Biblioteca Vallicelliana D.38 (9c, ecclesiastical province of Reims) are some of the best manuscripts of Class A2.
Three more versions date from the 11th or 12th century:
- Hinschius class B (e.g., Boulogne-surhhayMer, Bibliothèque municipale 115/116),
- Hinschius class C (e.g., Montpellier Bibliothèque de l'École de Médecine H.3)
- and, finally, a version mixing A2 and the Cluny version (e.g., Paris Bibliothèque nationale lat. 5141).
It is hard to say which manuscript class represents the "genuine" forgery, so to speak. The fact that A1, A/B, the Cluny version and A2 all date to the ninth century might be an indication that the forgers circulated their work from the very beginning in several different versions. It would have been the typical behavior of forgers to increase insecurity by circulating many different versions, thereby decreasing authority of anyone intending to call out the forgery, for no one could tell which version was a forgery and which was not.
- Printed in J. B. Pitra, Spicilegium Solesmense 4, p. 166ff, erroneously treated as a work of an African bishop.
- Schaff, Philip. "Pseudo-Isidorian Decretals and Other Forgeries". New Schaff-Herzog Encyclopedia of Religious Knowledge, Vol. IX: Petri - Reuchlin. Hosted at the Christian Classics Ethereal Library.
- Zechiel-Eckes, K. (2002). "Auf Pseudoisidors Spur, Fortschritt durch Fälschungen?". MGH Studien und Texte 31. p. 1ff.
- An incomplete overview listing 80 manuscripts can be found in: Williams, Schafer (1973). Codices Pseudo-Isidoriani, A Palaegraphico-Historical Study, Monumenta Iuris Canonici. Series C. Volume 3.
- This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Decretals". Encyclopædia Britannica (11th ed.). Cambridge University Press.
Further reading 
- Fuhrmann, H. (1972-73). "Einfluß und Verbreitung der pseudoisidorischen Fälschungen". Schriften der Monumenta Germaniae Historica 24(i-iii).
- Fournier, P.; Le Bras, G. (1931-32). Histoire des collections canoniques en occident. Volumes I-II.
- Saltet, L. (1909). "False Decretals". The Catholic Encyclopedia. New York: Robert Appleton Company.
- "Projekt Pseudoisidor" (online edition of the False Decretals), Monumenta Germaniae Historica. (German) (Latin)
- The False Capitularies of Benedictus Levita, Monumenta Germaniae Historica. (German) (Latin)
- "Opera Omnia" by Migne Patrologia Latina, with analytical indexes. (Latin)
- "Reading Pseudo-Isidore", a blog devoted to the False Decretals.