Unlike most religions in the Roman Empire, however, Christianity required its adherents to renounce all other gods, a practice adopted from Judaism (see Idolatry). The Christians' refusal to join pagan celebrations meant they were unable to participate in much of public life, which caused non-Christians—including government authorities—to fear that the Christians were angering the gods and thereby threatening the peace and prosperity of the Empire. The resulting persecutions were a defining feature of Christian self-understanding until Christianity was legalised in the 4th century.[168]
In 313, Emperor Constantine I's Edict of Milan legalised Christianity, and in 380 the Edict of Thessalonica made Catholic Christianity the state church of the Roman Empire which would persist until the empire itself ended with the Fall of Constantinople. During this time (the period of the Seven Ecumenical Councils) five primary sees emerged, an arrangement formalised by Emperor Justinian I as the pentarchy of Rome, Constantinople, Antioch, Jerusalem and Alexandria.[169][170] On 11 May 330, Constantine moved the imperial capital to Constantinople, modern Istanbul, Turkey, and in 451 the Council of Chalcedon, in a canon of disputed validity,[171] elevated the see of Constantinople to a position "second in eminence and power to the bishop of Rome".[172] But from c. 350 to c. 500, in spite of these developments, the bishops, or popes, of Rome, a city no longer the capital of the empire, steadily increased in authority.[173]