Arius denied the Divinity of the Lord Jesus Christ; he considered that Christ was not consubstantial with the Father and that He was created. The roots of Arianism still exist until this day. Even after being condemned in 325 A.D. by the Council of Nicea, Arius and his followers caused trouble, dissension and suspicions within the Holy Church.

B) The Heresy of Apollinarius:

Apollinarius preached the Divine Nature of Christ, but did not believe in His complete human nature; he considered that the human nature of Christ was not in need of a soul and thus He was without soul because God the Logos provided the needed life. As this implied that the human nature of Christ was incomplete, the Holy Ecumenical Council of Constantinople held in 381 A.D. condemned Apollinarius and rejected his idea declaring it a heresy.

C) The Heresy of Nestorius (Nestorianism):

Nestorius was Patriarch of Constantinople in 428 A.D., he was excommunicated by the Holy Ecumenical Council of Ephesus held in 431 A.D. because he refused to name the Virgin St. Mary "Mother of God" (Theotokos). He believed that St. Mary gave birth to a mere human and that Divinity descended and filled this human; Thus the Virgin Mary would be called the "Mother of Jesus" (Christokos), and not the "Mother of God" (Theotokos). Nestorius’ priest, Anastasius, spread this teaching; and Nestorius then confirmed it and wrote five books to refute the idea that the Virgin was the "Mother of God". In doing so he is considered to have denied the Divinity of Christ. His theory that Divinity descended and filled Our Lord meant that there was no Hypostatic union, but rather meant that the Divinity descended to accompany Him or to fill Him as in the case of saints. In other words, Nestorius’ concept meant that Christ became a dwelling for God just as He became a dwelling for the Holy Spirit through His Baptism. As such, Christ is considered a "Carrier of God" (Theophorus), which is the same title given to St. Ignatius of Antioch. He Explained that it was impossible for the Virgin to give birth to God, as the creation never gives birth to the Creator. Besides, whatever is born of flesh will merely be flesh. Thus the opinion of Nestorius was that the relation between the human nature of Christ
and the Divine nature started just after His Birth from the Virgin and it was not a Hypostatic union. He explicitly said: "I distinguish between the two natures". In this way the Nestorian belief is against the Propitiation Creed, because if Christ has not united with the Divine nature it would have been impossible for Him to offer anunlimited propitiation (or sacrifice.) sufficient for the forgiveness of all sins of all people
throughout the ages. When our Church says that the Virgin is the "Mother of God", it confirms that she
gave birth to the Incarnate Logos and not that she was the source of the Divine nature. Certainly not.
God the Logos is the Creator of the Virgin, but He, in the fullness of time, descended and filled her and she became pregnant and carried Him united with the human nature and she gave birth to Him.
The twelve Anathemas which St. Cyril issued include answers to all the Nestorian heresies. He condemned those who said that the two natures resulted from being joined together and those who said that God the Logos was working in the man Jesus or that God the Logos was dwelling in Jesus. He also condemned those who distinguished between Jesus and God the Logos claiming that He was merely a man born of a woman.

D) The Heresy of Eutyches (Eutychianism):

Eutyches was an archimandrite of a monastery in Constantinople. He zealously opposed the Nestorian heresy and was so highly concerned about the unity of the two natures in Christ, which Nestorius tore apart, that he fell into another heresy. Eutyches said that the human nature was absorbed and dissolved in the Divine nature as a drop of vinegar in the ocean. In this way, he denied the human nature of Christ. After St. Dioscorus had excommunicated him, Eutyches pretended that he repented and
accepted the true faith and St. Dioscorus allowed him to return on the condition that he would refute his heresy. Later on however, he again declared his corrupt belief and was condemned by the Council of Chalcedon held in 451 A.D.

The Council of Chalcedon:

In spite of the fact that the Council of Ephesus had excommunicated Nestorius, the Nestorian roots extended to influence the council of Chalcedon where the trend to separate the two natures became so apparent that it was said that Christ is two persons, a God and a human being; the one works miracles and the other accepts insults and humiliation. Following the same trend, Leo, the Bishop of Rome, accordingly declared his famous Tome which was rejected by the Orientals. But the Council accepted and voted for it, thus confirming that two natures existed in Christ after their unity: a Divine nature
performing its functions and a human nature carrying out its role. Nestorius claimed that those two natures were distinctly separate. The Cartage’s Council proclaimed their union but Nestorius separated them by this explanation. Just as he concluded that Christ had two natures, he also concluded that He had two wills and two lines of action. The problem of the two natures and two wills has its roots here and thus began disruption and conflict within the Church.