Doctrine matters, and no doctrine matters more than the doctrine concerning Jesus Christ.
Nestorius was the last of the major Christological heretics in the early church. He objected to the church’s declaration that Mary was the “God-bearer,” the “theotokos.” No human being can give birth to God, he thought, and he preferred to say that Mary was “Christ-bearer.”
At the Council of Chalcedon, the church insisted on the term “God-bearer” and addressed the larger questions of Nestorianism by saying that the divine and human were united without confusion in the one Person of Jesus Christ, the Incarnate Son.
So what? What does matter if Mary was God-bearer or not?
It matters because it shapes the way we read the gospel story. Is the gospel story about a man working in tandem with God, or is it the human history of God? Is the birth of Jesus a purely human birth, or is it the human birth of God? Is the death of Jesus only a human death, or is it the human death of God?
Behind all these questions is the question of whether God actually entered human life. Nestorius could not believe that God entered into such close intimacy with creation. The church disagreed: God the Son entered fully into human life, from conception through death to the grave. He lived human life from the inside to redeem human life. What is not assumed is not redeemed.
Advent is a season of preparation, which includes repentance. During this Advent season, examine yourself and repent not only of your sinful actions but your false beliefs, and especially your false beliefs about Jesus. ~ Peter Leithart