"The Final Victory" (commentary on González, chapter 12)
Diocletian sought to consolidate support by (a) social, economic, and organizational improvements, and (b) religious unity

• He was successful at the first. Among his reforms was the appointment of a senior and junior emperor ("augustus" and "caesar") for each of the east and west divisions of the Empire.
• He was not successful at the second, since his own assistant emperor, Galerius, persuaded him that the way to religious unity was to suppress the Christian movement (edict of 303). It proved too late to do this, because Christianity had already made too many inroads into the court (including Diocletian's own wife and daughter), the administration, the military, the intelligentsia, and so on, and the brutal persecution of Christians raised a backlash of sympathy for them. (There is no real demographic evidence for González' assertion, p. 101, that the Church at this time was still "composed mostly of humble folk".)
• Diocletian retired in 305. Galerius carried on the persecution, but recognized its failure on his deathbed, proclaiming an edict of toleration in 311.

At this point, Constantine comes onto the stage of history.

• He was the son of the junior emperor of the west, who was being "educated" (i.e. held hostage) in the eastern court, until he escaped, joined his father, and won the support of the western military.
• He fought against the senior emperor of the west. The night before the crucial battle, at the Milvian Bridge over the Tiber River a few miles north of Rome (Oct. 28, 312), he had a vision narrated by González. He won the battle, and attributed his victory of the power of Christ. Afterwards he supported the Church.
• With the eastern emperor Licinius, he issued an edict of toleration of Christianity in 313.

Constantine (commentary on González, chapter 13)

Was Constantine a sincere supporter of Christianity?

• González is skeptical. He says Constantine may have wanted the power of the Christian God on his side, but he continued to take part in pagan rites, refused to receive the instruction of bishops, and was not technically a believer because he wasn't baptized.
• I would be less skeptical. Although he accepted the pagan priestly title "pontifex maximus", he did not offer sacrifice, and did not permit himself to be regarded as a god, as other recent emperors had done. He did have episcopal advisers. And delaying baptism was a fairly common practice. Moreover, he went out of his way to support the Church and its bishops. Most radically, he gave ecclesiastical courts jurisdiction in civil litigation.

What was his conception of Christian empire ?

• We can't easily distinguish Constantine's contribution to the idea of Christian empire from the historian Eusebius'.
• To the extent that we can, González indicates that Constantine wanted to restore the old glories of the Roman Empire, but on a Christian basis (p. 118).
• I'm not sure this goes far enough. In refusing to be seen as a god, and in giving his support to the Church, Christian doctrine, and the Church's social service, and in giving judicial jurisdiction to the Church, he was de-absolutizing the Empire. Imperial power was no longer for its own sake, or for the sake of the Emperor and the Emperor's glory, but for the glory of God.
• This ideal of Christian Empire can be seen preserved and developed through the Middle Ages, in the England of Henry VIII, in the theocratic theology of Luther and Calvin, in the messianism of the Russian Empire, and even in the ideology of the successor of the Roman Empire, Soviet Communism.

Is the ideal of Christian Empire appealing or otherwise?

• Pro: it sets moral bounds on the State; it puts justice and the protection of the helpless on the political agenda; the Emperor himself became subject to the rule of law, as we will see a few decades later in the confrontations between Ambrose, bishop of Milan, and the Emperor Theodosius. The anti-Church empires of the twentieth century — the Nazi, Stalinist, and Maoist régimes — testify by their excesses to the value of imposing moral standards on the State.
• Con: the Church's agenda becomes co-opted by the imperial agenda; nominal Christianity flourishes, and the worldly ambitions of Church and clergy blossom beneath the camouflage of pious language. Theology degenerates into a system for rationalizing the worldly self-interest of the Church's power structures.

Constantine and Nicea
In 324, Constantine succeeded in becoming the one ruler of the entire Empire.

In 325, he called together the bishops of the Church to a council at an imperial palace in Nicea (in modern Turkey) to make decisions on a variety of divisive issues. Previously, no authority existed which could settle matters of doctrine and discipline for the whole Church.

The most important of the divisive issues was Arianism, which denied the divinity of Christ. It is named after Arius, a presbyter of Alexandria.

• It was trying to protect the unity of God and feared that the divinity of Christ would make two Gods.
• It was also trying to make sense of those parts of Scripture suggesting the subordination of Christ, e.g.: "No one knows the hour except the Father." "Why do you call me good? No one is good but God alone."
• Arians said: "There was [a time] when he [the Son of God] was not."

Others, like Alexander, the bishop of Alexandria, and Athanasius, his deacon, argued from other parts of Scripture (such as John 1), the fact that Christians worshipped Christ, and the experience of redemption in Christ, that the Son must be divine.

The Council of Nicea promulgated the first two articles (paragraphs) of the Nicene Creed. It is said that Constantine himself supplied the word "homoousios" ("being of one substance with the Father"). Nicene doctrine was widely attacked for the next fifty years.