c.386 - c.451
Nestorius was Patriarch of Constantinople.
He started a theological debate by not recognizing Mary as the mother of God, on the grounds that it compromised Jesus' divinity.
His views were condemmed by Cyril, bishop of Alexandria, and a Council at Ephesus (431) exiled him to a monastery in the Libyan desert.
This led to a split within the church and to the creation of separate Nestorian churches that flourished in the Middle East and central Asia.
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From the Catholic Encyclopedia: