Below are extracts from Boyd’s 1905 book about the union of church and state and the role which the Roman emperors played in church affairs. Boyd’s book was a historical treatise and, therefore, less suspect to theological contamination. The full script may be obtained from:
The headings below I added myself:
“The source of our knowledge of this subject is the Theodosian code” (p10); P12 “the codification of imperial constitutions since Constantine (published 438)” (page 12).
[Note: This was not the famous Theodosius I that became emperor in 379, but “Theodosius the Younger (408-450)” (page 11).]
Union of Church and State
“The blending of civil and ecclesiastical authority in the later Roman Empire is a subject of vast and permanent historical interest. … There is one phase of this union of secular and religious forces … the ecclesiastical edicts of Constantine and his successors.” (page 9)
“The legislation which severed the alliance that, for ages, had united the Roman government with the ancient pagan religious systems, has been noted. … It was, however, only one phase in the ever-increasing influence of the church. … Constantine established the precedent for imperial intervention in ecclesiastical affairs … while Gratian and Theodosius finally and decisively fixed the alliance of the state with ecclesial creed and persecution.” (page 33)
“The political and social power acquired by bishops … made their election in the days of the later Roman Empire … a matter of public importance. … Consequently the election of patriarchs was often the occasion of an ecclesiastical synod and the emperors, through their relation to the synods, which they often convened and attended, might exercise a direct influence on elections. Constantine wrote to the council and people of Antioch not to choose Eusebius of Caesarea as bishop of that city. Constantius convened ‘an assembly of bishops of Arian sentiment’ and deposed Paul of Constantinople” (page 64).
“Constantine gave the episcopal (papal) courts a place in the judicial system of the empire. … the episcopal arbitration was transformed into a legal mode of procedure. … the place given him (the bishop) in the system of justice was similar to that of the judges of the public law courts. … Moreover, the conception of his office as arbitrator was that of an authority transcending (exceeding) the regular civil courts.” (pages 90-91)
Why emperors became involved in church matters
“Since Constantine desired that the church should contribute to the social and moral strength of the empire, religious dissension was a menace to the public welfare, and if necessary, secular authority might be exercised for its suppression.” (page 34)
“The same desire to preserve unity within the church, rather than the protection of any creed or interpretation of Christian doctrine, led Constantine to intercede for the settlement of the Arian controversy. … Believing ‘disunity in the church” a danger to the state “more grievous than any kind of war,” Constantine …” (page 37)
A consequence of the Nicene Creed
“The creed of Nicaea, sanctioned by imperial decree … only added increased confusion and complication to the problem it was intended to solve.” (page 38)
“A far more drastic policy toward heresy was persued by Theodosius. He issued an edict …” (page 44).
Note: This refers to the Edict of Thessalonica – Wikipedia of which Theodosius and his co-rulers issued in February 380. See that page for a discussion.
“In January of the following year, another edict forbade the heretics to settle in the cities … and (that) the Nicene faith … to be always maintained. In the same year, after the reformulation of the Nicene doctrine by the Council of Constantinople, which was convoked by the emperor to adjust problems of doctrine, the procouncil of Asia was ordered to deliver all churches to these bishops ‘who profess that the Father, Son and Holy Spirit are one majesty and virtue, the same glory, one light making no confusion by profane division’.” (pages 45-46)
Note: It is interesting to analyze the differences between this wording and the Creed of the First Council of Constantinople (381).
“The Arians did not surrender without protesting their right to exist. In the east, ‘great disturbances arose as they were ejected from the churches'” (page 46)
“The case frequently cited as typical of the conditions and opinions of the age regarding the treatment of heretics, is the execution of Priscillian and the execution of his followers. In 384 Priscillian was condemned by the synod of Bordeaux for teachings tainted with Manichaeism. … Maximum, the usurping Augustus of the West … appointed the Prefect Ennodius to conduct the trial (in a secular court) … Priscillian was found guilty of magic … Priscillian was put to death by the sword, and a number of his followers were executed or exiled. Not till the fifth century … was the death penalty for heresy justified by ecclesiastical theory” (pages 60-61).
Note: Boyd cites Sulpicius Severus Chronicon, ii, 46, 5 as source for the persecution of Priscillian.