c. 245–250
Latin
On the Trinity
De Trinitate
Novatian · c. 200–c. 258
A careful exposition of the rule of faith: God the Father almighty, the Son who is truly God and truly man, and the Holy Spirit — written before the vocabulary of Nicaea existed.
201–300
The Third Century
2 works
251
Latin
On the Unity of the Catholic Church
De Unitate Ecclesiae
Cyprian of Carthage · c. 210–258
Written during a schism over how to receive Christians who had lapsed under persecution. Cyprian argues that the church's unity is not an aspiration but a given, and that a bishop who breaks from it takes nothing with him.
301–400
The Fourth Century
1 work
c. 366–384
Latin
Against the Donatists
Optatus of Milevis
An argument that the North African schismatics have separated from a church that is catholic by definition, and that the validity of a sacrament does not depend on the holiness of the minister.
Western · Polemic
401–500
The Fifth Century
1 work
c. 400–401
Latin
On Baptism, Against the Donatists
Augustine of Hippo · 354–430
An argument that a sacrament belongs to Christ and not to the minister, so a baptism performed by a traitor or a heretic is still a real baptism.
Western · Polemic
501–600
The Sixth Century
1 work
547–548
Latin
In Defence of the Three Chapters
Facundus of Hermiane · 6th century
Twelve books arguing that condemning long-dead theologians to appease the Miaphysites betrays Chalcedon, addressed to the emperor who was doing it.
Western · Polemic
801–900
The Ninth Century
1 work
c. 885
Greek
The Mystagogy of the Holy Spirit
Photius of Constantinople · c. 815–c. 893
A sustained argument that the Spirit proceeds from the Father alone, and that the Latin addition to the creed is both unauthorised and incoherent.
Byzantine · TheologyJohn
901–1000
The Tenth Century
1 work
969
Latin
The Embassy to Constantinople
Liudprand of Cremona · c. 920–972
A furious report of a failed diplomatic mission — bad wine, worse lodgings, humiliating protocol, and a Byzantine emperor who called the Western ruler no emperor at all.
Western · Report
1001–1100
The Eleventh Century
2 works
1053
Greek
Letter Against the Latin Usages
Leo of Ohrid · 11th century
A protest against Western practices — unleavened bread at the eucharist, fasting on Saturdays, no alleluia in Lent — sent to a bishop in southern Italy.
Byzantine · Letter
16 July 1054
Latin
The Bull of Excommunication
Humbert of Silva Candida · c. 1000–1061
The document a papal legate laid on the altar of Hagia Sophia, excommunicating the patriarch and his followers in intemperate terms — its author's authority already lapsed, the pope having died.
Western · Decree
1101–1200
The Twelfth Century
1 work
1149
Latin
The Dialogues
Anselm of Havelberg · c. 1100–1158
A record of debates held in Constantinople with a Greek archbishop on the filioque and papal authority, prefaced by an argument that the church legitimately changes over time.
Western · Dialogue
1301–1400
The Fourteenth Century
4 works
1378–1379
Latin
The Declarations of the Great Schism
The cardinals of Rome and Avignon
The competing manifestos of 1378: one body of cardinals declaring Urban VI validly elected, the same body months later declaring the election void under duress and choosing another.
Western · Declarations
1380
Latin
Letter of Concord
Epistola Concordiae
Conrad of Gelnhausen · c. 1320–1390
An argument that a general council may be summoned without a pope's consent when the church's welfare requires it, since the church is greater than any officer of it.
Western · Political theory
1379–1381
Latin
Letter of Peace
Henry of Langenstein · c. 1325–1397
A call for a general council to judge both claimants, arguing that neither obedience can be certain and that the faithful must not be left in doubt about their own sacraments.
Western · Political theory
c. 1379–1381
Latin
On the Schism
Pierre d'Ailly · 1351–1420
Early writings on the schism arguing that the church cannot be bound to an uncertain obedience, and that a council represents it more fully than a doubtful pope.
Western · Political theory
1401–1500
The Fifteenth Century
4 works
1409
Latin
On the Unity of the Church
Jean Gerson · 1363–1429
An argument that the church may act to heal itself when the papacy will not, since the church exists for the salvation of souls and not for the convenience of its officers.
Western · Political theory
1410
Latin
On the Ways of Uniting and Reforming the Church
Dietrich of Niem · c. 1345–1418
A distinction between the universal church, which cannot err, and the Roman church, which plainly can — with the conclusion that a council may depose both claimants.
Western · Political theory
c. 1410
Latin
On the Long Schism
Dietrich of Niem · c. 1345–1418
A curial official's insider history of the schism, naming names and describing the financial machinery of the rival papal courts without much charity.
Western · History
6 April 1415
Latin
Haec Sancta Synodus
The Council of Constance
A decree declaring that a general council holds authority immediately from Christ, and that everyone including the pope must obey it in matters of faith, schism, and reform.
Western · Decree
1601–1700
The Seventeenth Century
1 work
1666–1667
Russian
The Acts of the Great Moscow Council
The Council of Moscow
The council that deposed Patriarch Nikon, confirmed his liturgical corrections, and anathematised those who kept the old rites and the two-fingered cross.
Rus · Decrees