"Edict of Thessalonica," also known as Cunctos Populos

The Emperors Gratian, Valentinian, and Theodosius, Augusti, an edict to the people of the city of Constantinople.

All peoples, whom the moderation of our mercy rules, we wish to remain in that religion which the divine Apostle Peter handed over to the Romans, the religion until now from him is very well known, and which clearly is followed by the pontifex Damasus and by Peter, Bishop of Alexandria, a man of apostolic holiness; that is, that, according to the apostolic teaching and the gospel doctrine, we believe in the single Godhead of the Father and the Son and the Holy Spirit, under equal majesty and under pious Trinity. We order that those following this law be included under the name of "Catholic Christians," but the rest (whom we judge to be demented and insane) will take on the disgrace of "heretical belief," and their little meetings will not receive the name of churches; they shall suffer as vengeance, in the first place, divine punishments, and after whatever we are moved to which we shall determine according to heavenly judgment. Given this day on the third of the Kalends of March [February 27] in Thessalonica by Gratian in his fifth and Theodosius in his first consulate [380 C.E.].

Imppp. Gratianus, Valentinianus et Theodosius aaa. edictum ad populum urbis Constantinopolitanae. Cunctos populos, quos clementiae nostrae regit temperamentum, in tali volumus religione versari, quam divinum petrum apostolum tradidisse Romanis religio usque ad nunc ab ipso insinuata declarat quamque pontificem Damasum sequi claret et Petrum Alexandriae episcopum virum apostolicae sanctitatis, hoc est, ut secundum apostolicam disciplinam evangelicamque doctrinam patris et filii et spiritus sancti unam deitatem sub parili maiestate et sub pia trinitate credamus. Hanc legem sequentes christianorum catholicorum nomen iubemus amplecti, reliquos vero dementes vesanosque iudicantes haeretici dogmatis infamiam sustinere nec conciliabula eorum ecclesiarum nomen accipere, divina primum vindicta, post etiam motus nostri, quem ex caelesti arbitrio sumpserimus, ultione plectendos. Dat. III kal. mar. Thessalonicae Gratiano a. V et Theodosio a. I conss.


Notes
Gratian: Emperor of Rome (367-383)

Valentinian (II): Emperor of Rome (375-395), half-brother of Gratian, nine years old at the issuing of this edict

Theodosius: Emperor of Rome (379-395), a general appointed by Gratian to rule with Valentinian, founder of a new dynasty

Augusti: title taken by senior emperors of the Roman Empire following the tetrarchy of Dioclectian

pontifex: in classical Roman religion, a senior priesthood; used by Christians as a title of respect for very prominent bishops by the late fourth century

Damasus: Bishop of Rome, 366-384

Peter: Bishop of Alexandria, 373-381; spent much of his time as Bishop in exile during the reign of non-Nicene emperors

"catholic": From the Greek word katholikē, meaning "universal"

"heretical": from the Greek word hairetikę, originally meaning "following a specific school of thought," in fourth-century Christian contexts meaning "of deviant belief"