TM Law has a few issues with Francesca’s reading of Isaiah and Matthew (referenced in her delightful BBC 5 interview earlier today). As I suggested in a little conversation with Mark Goodacre and TM on the facebook on the subject, I don’t think at all that Matthew was so uninformed that he didn’t have a good enough grasp of Hebrew to know what Isaiah was saying.
The use of parthenos by Matthew is unquestionably a claim that Jesus was born of a virgin. But the claim is not based on a mistranslation, as Stavrakopoulou suggests. The Greek translator of Isaiah used a perfectly acceptable rendering for עלמה. It is more likely that there was already a virgin birth oral tradition, related to other Greek myths in the Greco-Roman world like that of the birth of Aeo (see e.g., Rösel, ‘Die Jungfrauengeburt des endzeitlichen Immanuel’, JBTh 6 , 135–51). The Gospel writer was able to refer to the citation of Isa. 7:14 when he gave his narration of the birth of Jesus, because his readers, whether or not they were aware of the semantic shift that had occurred in the short history of this little Greek word, knew that in the first century parthenos indeed meant ‘virgin’.
I also understand that Mark will soon post a podcast on the very same issue. So stay tuned.