Early Christianity and the Persecutions

Christians were persecuted under Nero (64), Domitian, Trajan, Decius (250), Valerian and above all Diocletian (303–311). Refusal to sacrifice to the emperor was treated as a crime against the state. The memory of the martyrs became the foundation of the church calendar and the veneration of saints.

Justin Martyr, Irenaeus of Lyons, Tertullian, Clement of Alexandria and Origen defended the faith before the pagans and articulated Christian teaching.

In 313 the emperors Constantine and Licinius granted Christians freedom of worship. The Church emerged from the catacombs; the era of the Ecumenical Councils began.