When you look at the Annunciation story in the gospel of Luke, you can see that the angel’s message is pretty astonishing.
“Do not be afraid, Mary, for you have found favor with God. Behold, you will conceive in your womb and bear a son, and you shall name him Jesus. He will be great, and will be called Son of the Most High, and the Lord God will give him the throne of David his father, and he will rule over the house of Jacob forever, and of his kingdom there will be no end.” (Luke 1:30-33).
I think that if most of us were in Mary’s position, it would take some effort to wrap our minds around what we had just been told. Moreover, as a virgin, Mary naturally has a hard time understanding exactly how she could become pregnant: “How can this be, since I have no relations with a man?” (1:34) She’s asking the obvious question, as we probably all would do in her place.
In some ways, I think the biggest question of this story is not why Mary doesn’t understand what the angel is saying, but how she willingly embraces the astonishing future that God is offering her. To do so must have taken tremendous faith, and a whole lot of courage, too.