ABSTRACT If we read the original sources written by the Christian apologists (Lactantius, Eusebius of Caesarea and others) we realize that the historical figure of Constantine was for the Church of the first times a breath of fresh air. Tortured by many centuries of persecution by the Roman Empire, the Church experimented a drastic change of his situation. In the year 312 Constantine obtained the victory over his enemy Maxentius in the Battle of Milvian Bridge. On the day before of the battle, as the Christian chronicles tell us, God spoke to the Emperor in his dreams and He promised the victory with the Chrismon symbol. Constantine won the battle thanks to the intervention of the God of that religious community that underwent the persecution by his predecessors. So he decides to free it of this oppression with the rewrite of Galerius’s document well-known like 'Edict of Milan' and later, he will convert his faiths. At that moment the Church will receive all the properties that the State had taken away in the persecutions and it will begin to configure his doctrine in a theological context dominated by the continuous conflicts of the heresies. In the Ecumenical Council of Nicea (325), the Church confronted of the most paradigmatic heresy, the Arianism that took away the divinity of Jesus, the Son. Constantine wanted the religious peace and he was a strong defender of the conciliar orthodoxy. The Trinitarian controversy was a danger in the social and theological order and caused continuous confrontations. During his reign Constantine intervened in the sessions of the Council of Nicaea and he achieved to impose the formula of the homoousios to define the equality of essence between the Father and the Son; the consubstantiality of the two hypostatic figures. With this, he resolved the Arian question. With his doctrine Arrio took away also the divinity of the Holy Spirit. With the Ecumenical Council of Constantinople I (381) this hipostatic figure has got the same dignity than the Son and the Father.
