Note though that the ambiguity is in the translation of Isiah, the prophet in the Old Testament, NOT in the translation of the gospels where it is unambiguous that Mary was a virgin in the sense that she had not had sex with a man. However the reason the virgin birth is important for Matthew is because it is supposed to fulfill the prophecy in Isiah. Which in turn indicates that the story about the virgin birth probably originated among Greek-speaking Jews.
