In my 13 years of apologetics, I have found there are some misconceptions that take some time to explain. At the same time, there are others that are very easy to explain. Mary having the title 'Mother of God' is one that I feel is very easy to explain.
Time and time again, someone will object to Mary being called the Mother of God. "How could Mary have created the Trinity? Wouldn't that make her a goddess? That is why you Catholics worship Mary, isn't it?!"
Ironically, the title 'Mother of God' has more to do with Jesus than with Mary. I will first give my easy answer and then go into some depth.
1. Jesus is God
2. Mary is the Mother of Jesus
3. Therefore, Mary is the Mother of God
Mary is not some sort of goddess of any kind. There is only God-Father, Son, Holy Spirit - Mary is not included in the Godhead. The title comes from the fact that Mary gave birth to Jesus who is God.
The problem started in the early days of the Church. People had finally found their freedom in 313 A.D. in the Edict of Milan and now theological discussions could be brought out into the open. The first question that people were asking was WHAT is this Jesus guy? Is He man, is He God? If He is both man and God, how much man and God is He? 50/50? 99/1?
At the Council of Nicaea (325 A.D.)it was decreed against the Arians that Jesus was "one in being with the Father." Meaning that, in fact, Jesus is God. Not some demigod or angel, but God. (Side Note: The Davinci Code said that it was at this council that Jesus was decreed to be God for the first time - this is 100% false. The Gospels, if anything, show that He is God and all of the early church fathers agreed on this fact.
In the next century (431 A.D.), another problem arose. There was a man named Nestorius who said that God would never live in the womb of a woman and that Mary gave birth to the man Jesus who was then possessed by the Son of God after He was born. The problem was that now we have two Jesus' - The man Jesus, and the Son of God Jesus.
All of these teachings are very common sense today. We all know there is only one Jesus. I don't know of anyone who says otherwise.
The objection to the title "Mother of God" only makes sense if you don't believe in the Divinity of Jesus.
Now someone out there is going to say - "Mary is the Mother of Jesus' humanity not his Divinity."
This objection is in error because mothers aren't mothers of natures, they are mothers of persons. The person Mary is the Mother of just happens to be God. No one in their right mind would say to their own mother - "You are just the mother of my nature, not my person." You would get a mouth full of soap I would imagine!
Is Mary ever called the Mother of God in the Bible? When Mary visits Elizabeth, Elizabeth exclaims - Luke 1:43: "And whence is this to me, that the mother of my Lord should come to me?"
Who is Elizabeth's Lord if not God Himself?
Catholic Answers has a great tract on Mary being the Mother of God and what the early Church said about the topic here: http://www.catholic.com/library/Mary_Mother_of_God.asp
I hope you that all have a blessed New Year. Thank you for reading my blog. Keep spreading the faith - one tidbit at a time.