By this name a collection of spurious letters of popes is designated. They were first brought into use in the 9th century, in connection with the so- called Spanish collection of canons and decrees. (See CANONS). The author of this collection placed at its head a spurious preface of Isidore Mercator (according to some manuscripts, Peccator), and for this reason they were ascribed, as early as the 9th century, to Isidore of Seville (q.v.). During the Middle Ages they were generally considered genuine, but in the 15th century doubts of their genuineness were expressed by Nicholas de Cusa, (See CUSA), and others, and in the 16th the Magdeburg centuriators (q.v.) and other Protestant historians so conclusively established their spuriousness that it is now admitted even by Roman Catholic writers. The birth-place, age, author, and motives of these letters are still controverted questions, and have called forth a large number of thorough investigations, by which several important points have been established with a high degree of probability. There is a large number of manuscripts (more than fifty) of this collection extant, and it is believed that a more careful study and comparison of them will lead to new results. The order of the documents, according to Codex Vaticanus (No. 630), a manuscript of the 12th century, is as follows: The preface is followed by a letter of Aurelius to Damasus, and the answer of the latter, both spurious; the Ordo de celebrando concilio, borrowed from the fourth Council of Toledo; a list of councils and a spurious correspondence between Jerome and Damasus. Then begins Part I, consisting of 50 apostolic canons; 59 spurious letters of the popes, from Clement to Melchiades (in chronological order); a treatise, De primitiva ecclesia et synodo Niccena, and the spurious Donation of Constantine. Part II begins with a section of the preface of the genuine Spanish collection of canons, and another section of the collection of Quesnel, and contains the Greek, African, Gallic, and Spanish councils, agreeing in all essential points with the Spanish collection. Part III begins likewise with a section of the preface of the genuine collection, which is followed by the decretals of the popes from Sylvester to Gregory II († 731); among them 35 spurious ones. The total number of spurious decretals in the collection is 94. Whether all of them belonged to the original collection, or whether a part were of later manufacture, is still a controverted point. The sources used by the compiler are the works of Cassiodorus and Rufinus, the Liber Pontficalis, the Vulgata, the works of the fathers, the theological literature up to the 9th century, the genuine decretals and decrees of councils, the so-called Capitula Angilrami (q.v.), and the Roman law collection, especially the Visigothic Breviarium Alaricaanum (see Knust, defontibus et consilio Psalm Isidoriane collectionis, Gottingen, 1832). The opinion of Rosshirt (Zu den kirchenrechtlichen Quellen des ersten Jahrtausends undzu denpseudoisidorischen Decretalen, Heidelberg, 1849) that the compilers used many more sources than are now known, and that most of the papal letters which are now generally considered as spurious were probably taken from other collections, has not met with much approval.
As this collection was used by the popes with great effect to amplify their power over the bishops, it was long a common opinion that the compilers aimed chiefly at confirming and enlarging the papal power; but this opinion is now universally abandoned. Others, especially modern Roman Catholic writers, as Mohler, Walter, and Hefele, attribute to the falsifier the "wish to put an end to the confusion and servitude of the Church, and the uncertainty of law in his times, by introducing a uniform code of ecclesiastical discipline, clothed with the prestige of antiquity." The most common opinion at present is that the compiler wished to free the episcopal power from dependence on the state, and to weaken, for the same purpose, the influence of the metropolitans and provincial synods. With regard to the time of the compilation, it has been established with certainty that it falls between 829 and 857. The author is not yet known. Benedict Levita, Otgar, archbishop of Mainz, and others, have been assumed. W The place where it was compiled was most probably the western part of the Frankish empire. The first mention of the collection is made in the proceedings of the Synod of Chiersy, in 857; and a few years later pope Nicholas I used it efficiently in his controversy with Hincmar, archbishop of Rheims. After the end of the 9th century numerous extracts were made, and they were received into all the large collections of canons, (See CANONS), made during the Middle Ages. As regards the influence of the false decretals, it has been overrated by those who believe that the primacy of the Roman popes is mainly due to this vast fraud; and, on the other hand, it is underrated by the Roman Catholic writers, who maintain that the pseudo-decretals produced no change in the discipline of the Church, and were only an expression of the tendencies of those times, which, without them, would have been developed in the same manner. The truth, as has been already intimated, probably is, that the pseudo-decretals were compiled for the purpose of furthering episcopal tendencies, in opposition to the rights of metropolitans and provincial synods, but that they also greatly contributed to the development of the Roman primacy, and were unscrupulously used by the popes for this purpose.
There are two editions of the false decretals, the first in the Collection of Councils by Merlin (tom. i, Paris, 1523), and the second in Migne's Patrologia Lat. tom. 130 (Paris), which is only a reprint of the former. See Ballerini (Opp. Leon. tom. 3, p. 215, ss.); Theiner, De pseudoisidoriana canonum collectione (Bresl. 1826); Wasserschleben, Beitrage zur Geschichte der falschen Decretalen (Breslau, 1844); Mö hler, aus und iuber Pseudoisidor (in his Gesammelte Schriften, Regensb. 1838, vol. i); Gfrö rer, Pseudoisidor (in Frei. burger Zeitschrift. far Theologie, vol. 17); Weizsacker, Hincmar und Pseudoisidor (in Zeitschrift fair theologische Literatur, 1858); and the Manuals of Ecclesiastical Law by Richter, Walter, Rosshirt, Phillips, and others.