=The sources of Church history= are partly original, in the shape of inscriptions and early documents; partly derivative, in the shape of traditions and researches in regard to primitive documents that have meanwhile been lost. Of greater importance to church history than the so-called dumb sources, _e.g._ church buildings, furniture, pictures, are the inscriptions coming down from the earliest times; but of the very highest importance are the extant official documents, _e.g._ acts and decisions of Church Councils, decrees and edicts of the Popes,--decretals, bulls, briefs,--the pastoral letters of bishops, civil enactments and decrees regarding ecclesiastical matters, the rules of Spiritual Orders, monastic rules, liturgies, confessional writings, the epistles of influential ecclesiastical and civil officers, reports by eye witnesses, sermons and doctrinal treatises by Church teachers, etc. In regard to matters not determined by any extant original documents, earlier or later fixed traditions and historical researches must take the place of those lost documents.--=Sciences Auxiliary to Church History= are such as are indispensable for the critical estimating and sifting, as well as for the comprehensive understanding of the sources of church history. To this class the following branches belong: _Diplomatics_, which teaches how to estimate the genuineness, completeness, and credibility of the documents in question; _Philology_, which enables us to understand the languages of the sources; _Geography and Chronology_, which make us acquainted with the scenes and periods where and when the incidents related in the original documents were enacted. Among auxiliary sciences in the wider sense, the history of the _State_, of _Law_, of _Culture_, of _Literature_, of _Philosophy_, and of _Universal Religion_, may also be included as indispensable owing to their intimate connection with ecclesiastical development. § 4.1. =Literature of the Sources.=-- a. =Inscriptions=: de Rossi, “Inscriptt. chr. urbis Rom.” Vols. I. II., Rome, 1857. b. =Collections of Councils=: Harduin [Hardouin], “Conc. coll.” (to A.D. 1715), 12 vols., Par., 1715. Mansi, “Conc. nova et ampl. coll.” 31 vols., Flor., 1759. c. =Papal Acts=: Jaffe, “Regesta pont. Rom.” (to A.D. 1198), 2 ed., Brl., 1881. Potthast, “Regesta pont. Rom.” (A.D. 1198-1304), 2 Vols., Brl., 1873. The Papal Decretals in “Corp. jur. Canonici.” ed., Friedberg, Lips., 1879. “Bullarum, diplom. et privil. SS. rom. pont.” Taurenensis editio, 24 vols., 1857 ff. Nussi, “Conventiones de reb. eccl. inter s. sedem et civ. pot. initæ.” Mogunt., 1870. d. =Monastic Rules=: Holstenii, “Cod. regul. mon. et. can.” 6 vols., 1759.