Pseudo-Isidore
Pseudo-Isidore is the conventional name for the unknown Carolingian-era author (or authors) behind an extensive corpus of influential forgeries. Pseudo-Isidore's main object was to provide accused bishops with an array of legal protections amounting to de facto immunity from trial and conviction; to secure episcopal autonomy within the diocese; and to defend the integrity of church property. The forgeries accomplished this goal, in part, by aiming to expand the legal jurisdiction of the Bishop of Rome.

Historical background
Pseudo-Isidore worked in the second quarter of the ninth-century, in the archiepiscopal province of Reims. A likely candidate is an ordination of Ebbo, then archbishop of Rheims. His sympathies lay with the rank-and-file Frankish episcopate. Decades of royally sponsored church reform had contributed substantially to the prominence and political importance of Frankish bishops; it also contributed to their legal vulnerability, as the reign of Louis I the Pious saw a series of sensational episcopal trials and depositions. Pseudo-Isidore was also heir to a long tradition of Carolingian church reform, and his forgeries also include a wide array of themes reflecting Frankish liturgical, doctrinal, educational and administrative aspirations.

Content
A major constituent of Pseudo-Isidore's output consists of a collection of forged capitulary legislation ascribed to Charlemagne and Louis the Pious. These False Capitularies, which consist mostly of excerpts from genuine biblical, patristic and legal sources, are false primarily in the sense that almost none of them were ever promulgated by the Frankish kings. Among the many genuine items are also select forged capitula that advance the Pseudo-Isidorian program. In a preface, the pseudonymous compiler, Benedictus Levita (Benedict the Deacon) claims that he found these neglected capitularies in the archives of the cathedral at Mainz; and that the former Archbishop Otgar of Mainz ordered him to collect this material for posterity. Because Benedict seems to acknowledge that Otgar is dead at the time of his writing, it has been possible to date his preface to the years after 847.

Pseudo-Isidore also developed a small series of more minor forgeries which we find as appendices in manuscripts of the False Decretals. These include the Capitula Angilramni, a brief collection on criminal procedure allegedly given to Bishop Angilram of Metz by Pope Hadrian I; and a series of excerpts from the Rusticus version of the Council of Chalcedon.

Authorship
The names assumed by Pseudo-Isidore, including Isidorus Mercator (conflated from the names of Isidore of Seville and Marius Mercator). Klaus Zechiel-Eckes claims that Pseudo-Isidore did important research at the library of the monastery of Corbie, in the Reims suffragan diocese of Amiens.

Zechiel-Eckes believed that the prominent theologian and abbot of Corbie, Paschasius Radbertus (abbot 842–847) was to be identified with Pseudo-Isidore; and that the earliest phase of work on the forgeries, amounting to a subset of the False Decretals, was completed in the later 830s. These theories once commanded wide support, but today they are increasingly disputed. Eric Knibbs has argued that older, traditional dating schemes, which placed the False Decretals in the 840s or early 850s, were essentially correct. Several decretal forgeries contain material that aims to justify Ebo in his episcopal translation to the bishopric at Hildesheim after 845. It has also emerged that the decretal forgeries incorporate many items from a mid-ninth-century Corbie manuscript of the works of Ennodius of Pavia, which would seem to preclude any dates for the decretal forgeries substantially before the 840s.

Manuscripts
Well over a hundred medieval manuscripts containing Pseudo-Isidorian material survive. The vast majority—around 100—carry copies of the False Decretals.

Influence
The final proof of forgery was provided by Calvinist preacher David Blondel, who discovered that the popes from the early centuries quoted extensively from much-later authors and published his findings (Pseudoisidorus et Turrianus vapulantes) in 1628.

References

Further reading
Fuhrmann, Horst. (1972–73). Einfluß und Verbreitung der pseudoisidorischen Fälschungen. Schriften der Monumenta Germaniae Historica 24/I–III (1972–73).
Fuhrmann, Horst. "The Pseudo-Isidorian Forgeries", in Wilfried Hartmann and Kenneth Pennington, eds. Papal Letters in the Early Middle Ages. History of Medieval Canon Law (2001), p. 135–195.
Harder, Clara.  Pseudoisidor und das Papsttum: Funktion und Bedeutung des aposotlischen Stuhls in den pseudoisidorischen Fälschungen (Cologne, 2014).
Hartmann, Wilfried and Gerhard Schmitz, eds. Fortschritt durch Fälschungen? Ursprung, Gestalt und Wirkungen der pseudoisidorischen Fälschungen. MGH Studien und Texte 31 (2002).
Knibbs, Eric. "Ebo of Reims, Pseudo-Isidore and the Date of the False Decretals," Speculum 92 (2017), p. 144–183.
Knibbs, Eric. "Pseudo-Isidore's Ennodius," Deutsches Archiv 74 (2018), p. 1–52.
Patzold, Steffen. Gefälschtes Recht aus dem Frühmittelalter: Untersuchungen zur Herstellung und Überlieferung der pseudoisidorischen Dekretalen (2015).
Schon, Karl-Georg. Die Capitula Angilramni: Eine prozessrechtliche Fälschung Pseudoisidors. MGH Studien und Texte 39 (2006).
Ubl, Karl and Daniel Ziemann, eds. Fälschung als Mittel der Politik? Pseudoisidor im Licht der neuen Forschung. MGH Studien und Texte 57 (2015).
Zechiel-Eckes, Klaus.  “Ein Blick in Pseudoisidors Werkstatt: Studien zum Entstehungsprozeß der Falschen Dekretalen mit einem exemplarischen editorischen Anhang,” Francia 28 (2001), p. 37–90.
Zechiel-Eckes, Klaus. Fälschung als Mittel politischer Auseinandersetzung: Ludwig der Fromme (814–840) und die Genese der pseudoisidorischen Dekretalen (2011).

External links
 The False Capitularies of Benedictus Levita, Monumenta Germaniae Historica. .
 "Opera Omnia" by Migne Patrologia Latina, with analytical indexes. 

9th-century Christianity
Canon law codifications
Forgers
Hoaxes in France
Unidentified people
Year of birth unknown