Jacob,
Isn't that what the original post quote is saying? It was fulfilled in Isaiah and it can be used to show God's working through Mary as a virgin in the same way?
Bruce,
Are you saying the the prophecy wasn't fulfilled in Isaiah? Wasn't it fulfilled in 8:3? I think most scholars, conservative and liberal, agree that the prophecy was fulfilled in 8:3.
I do agree with you that the fact that the Pharisees were expecting a virgin-born messiah is an argument in favor of Matthew's interpretation, but I believe the fact is that it was fulfilled (in a sense) in 8:3.
I'm more than open to being wrong.
[Edited on 3-3-2005 by Juice]