Mary the Mother of God

One of the four Catholic dogmas concerning Mary is that she is the "Theotokos", the Mother of God. This dogma was solemnly defined by the Council of Ephesus in AD 431. Many Protestants resist or dispute this dogma because they think that it is somehow blasphemous to refer to Mary, a creature, as the mother of God, the Creator. This is, however, exactly as "blasphemous" as the Incarnation of God; indeed, it is inseparable from the doctrine of the Incarnation. In a simple syllogism it is irrefutable:

Jesus is God
Mary is the Mother of Jesus
Mary is the Mother of God

To deny this dogma you must do one of the following:

1. Deny that Christ is God, which is heresy
2. Deny that Christ is fully human and fully God and the natures cannot be divided, which is heresy
3. Deny that Jesus was the son of Mary, which is heresy

This dogma is explicitly biblical, as Elizabeth venerated Mary under the direct inspiration of the Holy Spirit in these words: "And whence is this to me, that the mother of my Lord should come to me?" - Luke 1:43. The Lord is a title of God. She was not saying that Mary was the mother of God the Father, nor the mother of the Holy Spirit. However, since Mary was the mother of Jesus, who is God the Son incarnate, it is impossible to deny this dogma without denying the dogma of the hypostatic union or the Incarnation itself.