Mertcan Bulak

Like his instructor, Nestorius rejected a popular designation of Mary as the “God-bearer, Mother of God.” His point was that Mary bore Jesus, but she did not bear God, whose existence precedes and is independent of Mary. He insisted that calling Mary “Mother of God” was tantamount to declaring that the divine nature could be born, or that God could be three days old.
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Those bishops in the premier cities of the empire—Rome, Constantinople, Alexandria, and Antioch—were considered highest of all and were called patriarchs. Generally speaking, Alexandria and Rome tended to support each other, and Antioch tended to align with Constantinople. On Alexandria’s part this reflected the jealousy that the proud and ancient city felt at the rise of Constantinople, the upstart capital in the East. Rome, too, while for the time content to extend its influence over the imperial dominions in the West, was not happy with the growing arrogance of the “New Rome” in the East. On the other hand, Antioch and Alexandria had long been rivals in the East.
The fifty years after Nicaea continued the heated debate over Arianism. A moderate group, sometimes called the Semi-Arians, broke away from the strict Arians and attempted to give a new interpretation to the one-substance statement. They used the term homoios , meaning “similar,” to describe the Word’s relation to the Father. Thus two parties arose. The one led by Athanasius insisted upon using homoousios because they believed that the Word (Christ) was of the “same” nature as the Father. If Christ had not been fully God, they said, he could not have fully saved us. The other party, the Semi-Arians, argued for homoiousios because they held that the Word was a being “like” God the Father.
Sometime around 318 Arius openly challenged teachers in Alexandria by asserting that the Word (Logos) who assumed flesh in Jesus Christ (John 1:14) was a lesser god who had a different nature than God the Father and that the Son was neither eternal nor omnipotent. He was a created being—the first created being and the greatest, but nevertheless himself created. Such teaching appealed to many of the former pagans; it was so much like the religion of their youth. Converts from paganism found it hard to grasp the Christian belief that the Word existed from all eternity and that he is equal with the Father. Arius made Christianity easier to understand.
No other major religion confesses or worships a three-in-one deity. Muslims and Jews find the doctrine offensive; Unitarians and Jehovah’s Witnesses find it deplorable. Christians themselves are hard pressed to explain what they mean when they sing of the “blessed Trinity.” Most are content to treat the doctrine as a piece of sublime mystery.