The Edict of Thessalonica in 380
The Edict of Thessalonica, also known as the Edict of Milan III, was a decree issued by Emperor Theodosius I in 380 AD that made Nicene Christianity the official religion of the Roman Empire. The edict stated that all people in the Roman Empire must profess the faith “delivered to the Romans by the divine Apostle Peter” and affirmed the doctrine of the Trinity. Image: Solidus of Roman Emperor Theodosius I
The Edict of Thessalonica, issued on February 27, 380 AD, by Emperor Theodosius I, marked a pivotal moment in the history of Christianity and the Roman Empire. The decree officially established Nicene Christianity as the state religion, while condemning other Christian doctrines, particularly Arianism, as heretical. It was the first secular law to explicitly define religious orthodoxy and authorized punitive measures against dissenters. The edict played a crucial role in shaping the religious landscape of the empire, influencing future church-state relations and reinforcing the close alliance between political power and Christian doctrine.
Background and Religious Conflict
Before the Edict of Thessalonica, the Roman Empire had experienced shifting religious policies concerning Christianity. In 313 AD, Emperor Constantine I and his eastern counterpart Licinius issued the Edict of Milan, granting religious toleration to Christians. However, this did not resolve internal disputes within Christianity, particularly regarding the nature of Christ’s divinity.
By 325 AD, the Arian controversy had gained significant traction. Arius, a Christian priest from Alexandria, argued that Christ was not of the same divine essence as God the Father but was rather a created being, albeit exalted above all others. This teaching challenged the developing orthodox Christian understanding of the Trinity, leading Emperor Constantine to convene the First Council of Nicaea. The council formulated the Nicene Creed, affirming that Christ was “true God from true God” and “of one essence with the Father.” This definition rejected Arianism but did not end theological disputes.
Even after the Council of Nicaea, Arianism remained influential, particularly in the Eastern Roman Empire. Successive emperors took different stances on the matter. Constantius II (337–361 AD) favored Arianism and even exiled some Nicene bishops. His successor, Julian the Apostate (361–363 AD), attempted to restore pagan religious traditions and promoted religious pluralism, undermining both Nicene and Arian factions. The brief rule of Jovian (363–364 AD) reinstated Christianity, but his successor, Valens (364–378 AD), who was sympathetic to Arianism, reignited religious tensions by promoting Arian doctrine.
By 379 AD, the balance shifted again when Theodosius I became emperor of the Eastern Roman Empire. Theodosius was a committed Nicene Christian, and his rise to power coincided with the Western emperor, Gratian, also enforcing anti-heretical policies. This set the stage for the decisive intervention of the Edict of Thessalonica in 380 AD.
Content of the Edict
The Edict of Thessalonica was jointly issued by the three reigning emperors:
- Theodosius I (Emperor of the East)
- Gratian (Emperor of the West)
- Valentinian II (Gratian’s junior co-ruler)
The edict declared that all peoples under imperial rule must adhere to the Nicene interpretation of Christianity, emphasizing belief in the Holy Trinity—God the Father, God the Son, and God the Holy Spirit, as one divine essence.
The decree specifically recognized the authority of Pope Damasus of Rome and Bishop Peter of Alexandria, both of whom were staunch supporters of Nicene theology. It commanded that all who followed this faith be called “Catholic Christians”, a term that distinguished them from heretical groups.
By making Nicene Christianity the official state religion, Theodosius I eliminated religious pluralism within the empire and criminalized alternative Christian doctrines
The edict harshly condemned those who rejected Nicene teachings. Those who held Arian or other non-Nicene beliefs were labeled “foolish madmen” and “heretics.” They were forbidden from calling their places of worship “churches” and were threatened with divine punishment as well as imperial retribution.
Text of the Edict (Excerpt)
The edict was written in Latin and later incorporated into the Codex Theodosianus (Book XVI, 1.2). The key passage stated:
It is our desire that all the various nations which are subject to our Clemency and Moderation, should continue to profess that religion which was delivered to the Romans by the divine Apostle Peter… and which is now professed by the Pontiff Damasus and by Peter, Bishop of Alexandria… According to the apostolic teaching and the doctrine of the Gospel, let us believe in the one deity of the Father and of the Son and of the Holy Spirit, in equal majesty and in a holy Trinity… We order the followers of this law to embrace the name of Catholic Christians; but as for the others… we decree that they shall be branded with the ignominious name of heretics.
This decree transformed the religious landscape of the Roman Empire, setting a precedent for state involvement in religious affairs.
Significance and Consequences of the Edict of Thessalonica
The Edict of Thessalonica, issued on 27 February 380 by Emperor Theodosius I, made Nicene Christianity the official state religion of the Roman Empire, condemning other Christian sects, particularly Arianism, as heretical. Image: A sculpture work depicting the bust of Theodosius I.
Establishment of Nicene Christianity as the Official Faith
The Edict of Thessalonica was the first imperial decree to explicitly mandate a specific Christian doctrine as the official state religion. While previous edicts had granted toleration, this law made adherence to Nicene Christianity compulsory, effectively outlawing religious dissent.
Legal Suppression of Heresy
The edict criminalized non-Nicene beliefs, declaring Arianism and other sects heretical and punishable. This led to state-backed persecution, including the confiscation of property, exile, and social marginalization for those who did not conform.
Church-State Alliance
The decree strengthened the alliance between the Church and the Roman state, granting bishops significant influence in imperial policies. This established the precedent for the Roman emperors to intervene in religious disputes, leading to the persecution of nonconformists and the increasing politicization of Christianity.
Though intended to unify the empire under a single faith, the Edict of Thessalonica also set a precedent for religious coercion, shaping the relationship between church and state for centuries to come.
The First Council of Constantinople (381 AD)
In 381 AD, Theodosius convened the First Council of Constantinople, which reaffirmed and expanded upon Nicene Christianity. This council condemned Arianism once again and formalized the Nicene-Constantinopolitan Creed, which remains a foundational statement of Christian faith.
The Edict of Thessalonica solidified the Church’s power, fostered state-backed religious persecution, and paved the way for medieval Christendom, where religious and political authority became deeply intertwined. Image: The emperor Theodosius I and a crowd of bishops seated on a semicircular bench at the First Council of Constantinople in 381
Long-Term Impact on European Christianity
The policies initiated by the Edict of Thessalonica reshaped medieval and Byzantine Christianity, influencing subsequent doctrines and church policies. It also set the foundation for Christianity’s dominance in Europe, contributing to the eventual establishment of the Papacy’s authority and the emergence of Christendom as a religious-political entity.
Frequently Asked Questions
Why was the edict significant?
It was the first imperial law to define Christian orthodoxy and paved the way for state-backed persecution of heretics, solidifying Nicene Christianity as the dominant faith of the empire.
Who issued the Edict of Thessalonica?
It was jointly issued by Theodosius I (Eastern Roman Emperor), Gratian (Western Roman Emperor), and Valentinian II, targeting religious unity in the empire.
What was the main religious doctrine endorsed by the edict?
The edict mandated belief in the Holy Trinity—Father, Son, and Holy Spirit as one deity—aligning with the Nicene Creed and rejecting Arianism.
How did the edict affect religious tolerance?
Unlike previous edicts that promoted tolerance, such as the Edict of Milan (313), the Edict of Thessalonica suppressed religious plurality by punishing non-Nicene Christians as heretics.
What was the political motive behind the edict?
Theodosius sought to unify his empire under a single faith to strengthen imperial authority and stabilize Constantinople, his intended imperial residence.
How did the edict influence later laws?
It was incorporated into the Theodosian Code and influenced subsequent legislation enforcing Nicene Christianity while criminalizing heretical sects.
What followed the Edict of Thessalonica?
In 381, the First Council of Constantinople reinforced the Nicene Creed, further solidifying Nicene Christianity as the empire’s religious standard.
