From Persecuted Minority to Rule by the Lord's Man 
Faced with growth of Christian churches, the empire had the choices of secularization (which was unthinkable), extermination (which had not worked), or conversion of the ruler to Christianity.6 What meaning would Christ's words about the image on the coin take on if Caesar himself were a Christian? After battling to win the rule of the whole empire, Constantine did convert. Because conversion was seen as a way of dealing with the growth of the Christian cult and because of his deathbed baptism, his status as a believer is often questioned. In answer one might note that the empire was not yet majority Christian, and the practice of baptism at the end of life was commonly considered a prudential way of cleansing all sin right before death.7 Constantine held the traditional Christian belief that God was the God of history and had revealed himself through the resurrection of Christ. He referred to the faith as "the struggle for deathlessness."8 Historian Henry Chadwick asserted that whether or not Constantine's grasp of the Christian faith was subtle, the ruler was quite certain that the Christian God was the author of his military victory over his rival Maxentius in Rome.9

Christians and non-Christians alike often speak disparagingly of Constantine's conversion, as though Constantine made Christianity the state religion and thus ruined the purity of the faith by corrupting it with power and wealth. Contrary to popular belief, however, Constantine did not impose the Christian religion on the empire.10 His regime is more accurately described as having embraced "provisional religious pluralism." He believed and said that "the struggle for deathlessness must be free."11 His legislation did favor the Christian church in some instances though. He gave residences to the bishops of Rome and gave large percentages of provincial revenues to be used in church charity. The law itself also took on a more Christian flavor. He generated greater protection for "children, slaves, peasants, and prisoners."12 He ended the practice of branding criminals' faces because of the image of God in man. Courts closed on Sundays unless there was a slave to be freed.

Although Constantine's Christian humanitarianism continued to influence the law, his policy of religious toleration gradually fell by the wayside in the West. For a long time afterward the church was possessed by a different view, which was that of the loving constraint of heresy and apostasy.

The Religion of the State, but Not the State's Religion 
Under Constantine, the church first escaped persecution and then gained the bounty of endorsement by the most powerful man in the empire. In the latter half of the fourth century, Theodosius did what Constantine had not, which was to set up a Christian state where heretics had their civil rights sharply curtailed and pagans were tolerated but controlled. Half a century later, Theodosius II made serious doctrinal divergences subject to the death penalty and no longer allowed pagans to serve in the army.13

Ambrose set a precedent for the independence of the church when he refused Communion to Theodosius for his massacre of townspeople in Thessalonika after an imperial officer was killed in a riot there. The emperor did penance.14 He was the head of the state but not the head of the church and lacked the power to absolve himself or to declare his actions right. The action not only established the church's independence but also showed that it was not a slave to its private interests.15

Augustine's State: Necessary Evil or True Justice 
Augustine was one of the first major Christian commentators to live in an empire that was to some degree a projection of Christianity rather than a threat to it. For that reason, perhaps, his assessment of the state was thoroughly mixed.

Augustine viewed the natural state as little more than the most successful power play in a world of theft and contest. In one justly famous passage, he remarked: