2. Why do Catholics call Mary Mother of God?

 Catholics do call Mary "The Mother of God," but this does not mean that Mary came before God. It does express our belief that Mary is truly the Mother of Jesus Christ, who from the first moment of his conception was both human and divine.

Catholics believe that God is a Trinity of Persons—Father, Son, and Holy Spirit--in one divine nature. We believe that God existed from all eternity and is the source of all created things.

We believe also that, to save us from sin, the Second Person of the Trinity, the Son (called the "Word" in the Gospel of John) took on a human nature. God became one of us in the mystery of the Incarnation (God-becoming-flesh).

The story of the Incarnation is related in the infancy narratives of the gospels of Luke and Matthew. Luke's gospel tells us that God sent the angel Gabriel to Mary, a young woman of Nazareth in Galilee. Gabriel announced that Mary would have a child, the Son of God, by the power of the Holy Spirit. Mary consented, and Jesus Christ was conceived in her womb. (Luke 1:26-38)

Mary then goes to visit her cousin Elizabeth, who greets Mary as "mother of my Lord." This greeting expresses the reality that the Lord, the God of the Old Testament, is present in the womb of Mary. (Luke 1:39-45) Other passages of the Bible testify to the same fact. Mary is the Mother of Jesus Christ (Matthew 1:18-25). Jesus Christ is God. (John 20:28) Therefore, Mary is Mother of God.

Jesus Christ's origins are both divine and human. The miraculous conception of Jesus in the womb of Mary was the moment when the immortal, eternal God took on a mortal body and entered our history. From the moment of his conception, Jesus was both God and human, and from that moment Mary has been Mother of God.

Therefore, belief in Mary as Mother of God is linked to belief in the reality of the Incarnation. This is a mystery which is beyond our understanding and must be accepted in faith. Some have refused to believe. Even in New Testament times there were those who denied that Jesus could be identified with God. (John 8:12-59) Others denied that Jesus was truly human, and they would not "acknowledge Jesus Christ as coming in the flesh." (2 John 7) Those who refused to accept either the divinity or the humanity of Christ also denied that Mary is Mother of God.

Early Church councils affirmed that Jesus is truly God and truly human. Further clarification came in the fifth century when Nestorius, the bishop of Constantinople, wrongly stated that there were two persons in Jesus Christ and that the Son of Mary could not be identified with the Son of God. A general council of bishops at Ephesus in 431 condemned the teaching of Nestorius and deposed him. It affirmed that Mary is truly Mother of God because "according to the flesh" she gave birth to Jesus, who was truly God from the first moment of his conception. The expression, "according to the flesh," made it clear that Mary is not the source of Jesus' divinity. She did not give birth to God from all eternity. But since Jesus is truly God and truly human, Mary is really the Mother of God. In 451 another council at Chalcedon stated these truths as dogma (official doctrine).

When we honor Mary as Mother of God, we are actually professing our belief that Jesus is truly God. We are not saying that Mary came before God. Rather, the Second Person of the Trinity, who existed from all eternity, "became flesh and made his dwelling among us." (John 1:14). The child foretold by Old Testament prophets, the child whom Elizabeth recognized as Lord, is Jesus Christ, our Lord and our God (John 20:28), and Mary is his Mother.