On the Milvian Bridge in October of 312, Emperor Constantine beheld a cross or a Chi Rho in the sky with the words “In this sign, conquer” below. He interpreted this as a vision from God, and after defeating his opponent Maxentius at the Battle of Milvian Bridge and gaining control of the whole empire he converted to Christianity and gave the religion favorable status in a nation where before it had been persecuted.
For the Christians of that time like historian Eusebius, Constantine was a righteous and just God-send. Constantine benefited Christianity in creating an environment for lawful practice and organizing projects for its advancement, but he also detrimented the Church and its mission as politics came into play in religious matters.
Through restoration of order and legislation, Constantine allowed for the spread and strengthening of Christianity in the empire. In the centuries previous political instability rocked the empire as invaders plundered the land and emperors competed among themselves for power. A trend since Nero to blame Christians for imperial woes resulted in persecutions that officially ended only two years before Constantine with Emperor Galerius’s Edict of Toleration.
After his 312 defeat of Maxentius and the later 324 defeat of the Eastern Roman emperor, Constantine consolidated power as the sole ruler of the Roman Empire, which position he defended against barbarians like the Franks and the Goths. The throne thus secure, Constantine could focus energy on his newfound faith. In the Edict of Milan in March 313 Constantine permitted the free practice of religion and restored land to Christians.
While in theory the edict assured “free and unrestricted practice of their religions…to worship God after his own choice”, in practice Constantine demonstrated obvious favoritism for Christianity and during the latter part of his reign had pagan temples destroyed. In contrast, Constantine passed several pieces of legislation in favor of the church. In a letter to proconsul Anulinus of Africa Constantine ordered the restoration of property to Christians, and at both home and abroad donated money for the building of churches.
His concern for church unity is evident in his summoning of the Council of Nicaea, which he hoped would settle the matter about the Trinity that divided the church. This council produced a unified creed that gave the Christians of the culturally diverse empire common ground in their doctrine. Thereby Christians could more freely and richly worship God in the empire after Constantine’s conversion.
As Constantine’s influence in religion strengthened Christianity’s standing, the collision of political and ecclesiastical affairs also weakened the Church. Making Christianity the favored religion transformed it from the faith of the outsiders to the religion of the powerful. As a result, the citizenship adopted Christianity out of social obligation rather than personal conviction. Half-hearted converts brought half-hearted conversions to church, which meant that Christian and pagan elements composed their religions.
The danger of pagan superstition permeating the Church rose. Heresies like Gnosticism that church councils combated during the medieval period, for example, may have had roots in the Egyptian religion Manichaeism. The new state of Christianity also attracted the politically ambitious, which threatened “secularization and misuse of religion for political purposes.” While less evident in Constantine’s time, during the later centuries of the Middle Ages political troubles like simony and nepotism assaulted the Church.
Another problem that emerged from his influence in the Church is the mingling of the Church in politics. As pontifex maximus Constantine had power in the appointment of clergy and the congregation of councils, as demonstrated by his gathering of the Council of Nicaea in 325. Rather than existing separately, the affairs of church and state often intertwined. As the Church grew in influence control shifted less into the hands of the secular authorities and more into the hands of the spiritual authorities, I.e., the pope and other clergy, it departed from its call to preach and worship and focused on holding power.
This political ambition began with Pope Leo I in the 5th century and reached an apex with Pope Gregory VII in 1076 and 1077 during the investiture controversy between him and King Henry IV. The intrigue naturally sowed corruption and the de-emphasis on doctrine opened the doors to bad doctrine. So it was that from the rise of Constantine to the dawn of the Reformation about a millennium later, emperor and pope vied for supremacy, one over the other, as a result of the close association between and power crossovers of the two, so that the Church became twisted in politics both within and without.
Though Constantine’s influence effected much good for the Christian church, the intervention of politics caused problems that included the secularization of Christianity and the politicization of the Church. Progressing in the Middle Ages, the Church added more and more corruptions to itself to secure and maintain power, which led to doctrinal deviations and missional negligence against which the reformers of the 16th century protested.