The First council of Nicea was held on 325 AD on the occassion of the heresy of Arius. The canons were written there. Also, the Nicean creed was formulated there.

The mail purpose of Nicea Council was to legalize the Roman Church beliefs (the worship of Jesus and veneration of Mary). The Emperor Constantine (the head of the Church, pontifex maximums, the 13th apostle…) the head of the Council wanted to unify the Eastern Church and Western Church (the Roma Catholic). Eastern churches did not believe in deity of Jesus and Arius was a great leader of a large Eastern denomination, later called a heresy. Hosius was the religious adviser of Constantine, probably Hosius wrote the Nicean Creed. Hosius was a worshiper of Jesus and Mary. Jesus was already known as God of Roman Church. When Constantine (Pontifex maximums) invited the bishops of west and east churches, there was no bishop with Jewish background among them. He did not want to meet them. The purpose of the council was not only to bring political peace between West and East but also separate Christianity from Judaism. Christianity as the religion of the Empire must have a different creed, God, rituals, festivals etc (Sabbath changed to Sunday; Pascha to Easter and Christmas was added). The monotheistic Christianity (represented by Arius) was too similar to Judaism therefore it was rejected. The Jewish-Christian communities like Ibionites were persecuted and disappeared. For pagans like Roman and Greece the invisible God of the Jews was not acceptable. God must have images and incarnations like their gods. The position of Mary was also very important because she was already known as the Mother of God (Madona).