The " false writings " referred to in the text include also the Pseudo-Isidorian Decretals , together with other forgeries . The Pseudo-Isidorian Decretals are certain fictitious letters ascribed to early popes from Clement ( A . D . 100 ) to Gregory the Great ( A . D . 600 ), incorporated in a ninth century collection purporting to have been made by " Isidore Mercator ." The name " Pseudo-Isidorian Decretals " has been in use since the advent of criticism in the fifteenth century .
Pseudo-Isidore took as the basis of his forgeries a collection of valid canons called the Hispana Gallica Augustodunensis , thus lessening the danger of detection , since collections of canons were commonly made by adding new matter to old . Thus his forgeries were less apparent when incorporated with genuine material . The falsity of the Pseudo-Isidorian fabrications is now incontestably admitted , being proved by internal evidence , investigation of the sources , the methods used , and the fact that this material was unknown before 852 . Historians agree that 850 or 851 is the most probable date for the completion of the collection , since the document is first cited in the Admonitio of the capitulary of Quiercy , in 857 .
The author of these forgeries is not known . It is probable that they emanated from the aggressive new church party which formed in the ninth century at Rheims , France . It is agreed that Bishop Hincmar of Rheims used these decretals in his deposition of Rothad of Soissons , who brought the decretals to Rome in 864 and laid them before Pope Nicholas I .
Among those who challenged their authenticity were Nicholas of Cusa ( 1401-1464 ), Charles Dumoulin ( 1500-1566 ), and George Cassender ( 1513- 1564 ). The irrefutable proof of their falsity was conveyed by David Blondel , 1628 .
An early edition is given in Migne Patrolgia Latina , CXXX . For the oldest and best manuscript , see P . Hinschius , Decretales Pseudo-Isidorianiae at capitula Angilramni ( Leipzig , 1863 ). Consult The New Schaff-Herzog Encyclopedia of Religious Knowledge ( 1950 ), vol . 9 , pp . 343-345 . See also H . H . Milman , Latin Christianity ( 9 vols .), vol . 3 ; Johann Joseph Ignaz von Doellinger , The Pope and the Council ( 1869 ); and Kenneth Scott Latourette , A History of the Expansion of Christianity ( 1939 ), vol . 3 ; The Catholic Encyclopedia , vol . 5 , art . " False Decretals ," and Fournier , " Etudes sure les Fausses Decretals ," in Revue d ' Historique Ecclesiastique ( Louvain ) vol . 7 ( 1906 ), and vol . 8 ( 1907 ).
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