[knarf]

I had to look up Nestorian theory>

He was a disciple of the church at Antioch, which was formed by persecuted followers of jesus and it was THEY that were first called Christian.

I'm not sure what the heresy of Nestor (?) was because it is clothed in miles of history.

It seems though to be around his belief that Jesus is true man as well as true God.

[lastchance]

See my answer to Editor Surveyor.

Orthodox Christianity both Catholic and Protestant believe that Jesus Christ is one person with two natures. This is known as the Hypostatic Union.

http://www.desiringgod.org/blog/posts/what-is-the-hypostatic-union

I think the above site is named after John Piper’s book. So I’ll assume it is vetted by Protestants.

[redgolum]

The Nestorian heresy is that he made Jesus two persons. One man, one God. The Hypostatic union is that Jesus was true God and true Man. But NOT two persons.

The term “mother of God” was used to illustrate that since Mary is the mother of Jesus, and Jesus is both true man and true God, she is the mother of God via the Incarnation of Christ.

It doesn't mean that the Son (the second person in the Trinity) did not pr exist the conception, but that Mary was the true mother Jesus. It is a foundational doctrine that most Western Christians hold, but not often expressed.