Christianity in late antiquity

Christianity in Late Antiquity covers the time from around 313 AD—when Constantine supported Christianity—until the fall of the Western Roman Empire in 476 AD. Some historians stretch this period to the late 500s, during Emperor Justinian’s reconquest of parts of the Western Empire.

 Persecution and legalisation 
Christianity first spread in Roman Judaea without any help from the government. In 311 AD, Emperor Galerius issued the Edict of Serdica, ending harsh persecution in the East. In 313, Constantine and Licinius issued the Edict of Milan, stating Christians could freely worship, and persecution by the state stopped.

Constantine had been influenced by his mother Helena and, in 312, reportedly saw a vision before battle that convinced him to support Christianity. He used his power to help the church: giving money, building churches, and sparing clergy from taxes. In 325 he called the First Council of Nicaea, the first major meeting of Christian leaders, which led to the Nicene Creed and began Christendom .

 State religion of Rome 
Even after Constantine died, Christianity was not fully united. His son Constantius II was an Arian Christian, and Emperor Julian later tried to restore old Roman pagan religious practices.

On February 27, 380, Emperor Theodosius I made Trinitarian Nicene Christianity the official religion of the Roman Empire. He declared that only followers of this creed were true Christians; all others were considered heretics and illegal. In 385, a heretic named Priscillian was executed—one of the first such punishments. From then on, the empire and later kingdoms persecuted many pagans and non‑Nicene Christians, although some Germanic tribes stayed Arian well into the Middle Ages.

 Theology and heresy 
During this period the church faced many debates about doctrine. Arguments centered on Christ’s nature: some believed his human side was only an illusion (Docetism), others that he was less than God (Arianism), or that the Father, Son, and Holy Spirit were simply forms of one God (Modalism). These debates led to councils and religious divisions.

 Theological councils 
Important councils met during Late Antiquity to settle these issues:
 First Council of Nicaea (325): defined the Creed and condemned Arianism.
 First Council of Constantinople (381): expanded the Creed to explain the Holy Spirit.
 First Council of Ephesus (431): declared Mary was truly the Mother of God.
 Council of Chalcedon (451): taught that Christ had two natures, divine and human.

 Biblical canon 
By the middle of the 2nd century, most Christians agreed on the key books of the New Testament, but discussions continued into Late Antiquity. In 331, Constantine asked Eusebius to prepare fifty complete Bibles for Constantinople. Manuscripts like Codex Vaticanus, Sinaiticus, and Alexandrinus came from this era.

 Monasticism 
Some Christians chose to live apart from society to focus fully on God. This movement, called monasticism, involved living in solitude (hermits) or in communities under rules (monasteries). St. Anthony the Great was a famous hermit. In 318, Pachomius organized the first monasteries with rules and leaders. Over time, figures like St. Basil in the East and St. Benedict in the West created systems that shaped European Christianity for centuries.

 Church structure within the Empire 
After gaining legal status, the church used the empire’s provinces as church territories, called dioceses, each led by a bishop. The most important cities were Rome, Constantinople, Jerusalem, Antioch, and Alexandria. By the 5th century, a system known as the “Pentarchy” recognized five leading bishops—Patriarchs—with Rome as “first among equals,” and Constantinople second. The Bishop of Rome (the Pope) was seen as the leader of the whole church .

 Christianity outside the Roman Empire 
Christianity also grew far outside Rome, especially in Persia. The Church of the East, sometimes called the Nestorian Church, became strong in Persia, India, and even China. It followed the teachings of Nestorius, focusing on the idea that Jesus’s divine and human natures were separate. This church remained active for over a millennium and often faced persecution.