The Church and the state at the end of the fourth century
After Theodosius had openly declared himself a follower of the Nicene Creed, he began his long and obstinate struggle with the pagans and heretics, inflicting upon them penalties which grew more harsh as time went on. By the decree of 380 A.D. only those who believed in the trinity of Father, Son, and Holy Ghost, as preached by the apostolic writings and the Gospels, were considered Catholic Christians; all others, the mad and insane people, who adhered to the infamy of heretic doctrine, had no right to call their meeting places churches and were subject to severe punishment. According to one historian, this decree shows clearly that Theodosius was the first of the emperors to regulate for his own sake, and not for the sake of the church, the body of Christian doctrine obligatory on his subjects. Theodosius issued several other decrees which definitely forbade the heretics to hold assemblies, either public or private; the right to assemble was reserved solely for the followers of the Nicene symbol, who were to take over all the churches in the capital and throughout the Empire. The civil rights of the heretics were greatly curtailed, especially those concerned with bequests and inheritance.
For all his partisanship, Theodosius was anxious to establish peace and harmony in the Christian church. For this purpose he convoked a council in the year 381 at Constantinople, in which only members of the eastern church participated. This council is known as the Second Ecumenical Council. Of no other ecumenical council is the information so inadequate. The proceedings (acts) of this one are unknown. For a while it was not even recognized as an ecumenical council; only in the year 451, at a later ecumenical council, was it officially sanctioned as such. The chief religious question discussed at the Second Ecumenical Council was the heresy of Macedonius, a semi-Arian who attempted to prove that the Holy Spirit was created. The council condemned the heresy of Macedonius, as well as a number of other heresies based upon Arianism; confirmed the declaration of the Nicene symbol about the Father and Son, adding to it the part about the procession of the Holy Spirit from the Father; and adopted the teaching that the Holy Spirit is of one essence with the Father and the Son.