I recently read a short book by Thomas Aquinas (it was against the Muslims and various other things). In this book, Aquinas describes how the fact that God can see everything (past, present and future) does not deny free-will. Aquinas describes it something like this:
If you are walking on a circular track, then you can see a little way ahead of you, but you only have a vague awareness of what is going on behind you. Now a person who is standing on a hill in the middle of the track can see everything happening on the track. This is God, who can see the whole track, but the person on the track can only see a little bit into the past, but really has no idea what will happen in the future.
My question is, how does free-will apply in the case of Mary? She must have had free-will, and so chose to do everything that she did. But what chance that she would spend her entire life sinless, in order to bear the Son of God? Did God just sit around waiting for an appropriate person to come along, or did the Immaculate Conception somehow ensure that Mary would be sinless her entire life?
Actually I think I may have just worked it out, but I would like to see what everyone else has to say about this. Thanks!