Hear, O house of David

13 And he said, “Hear then, O house of David! Is it too little for you to weary men, that you weary my God also? 14 Therefore the Lord himself will give you a sign. Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel. (Isa 7:13-14).

To critics, the Christian interpretation is special pleading. One argument for the 8C identity of the son is the claim that the sign child is something Ahaz must see or will see. There are, however, some basic problems with that argument:

i) How does a normal pregnancy constitute a sign? How would Ahaz even know which mother and child embodied the sign? Surely there were lots of candidates. Lots of pregnant women.

ii) Actually, the oracle isn't directed at Ahaz but the house of David. That's certainly broader than Ahaz and open to a longitudinal fulfillment. The house of David will witness the sign. 

iii) By way of reinforcement is the use of the second person plural in vv13-14. So, once again, the oracle isn't addressed to Ahaz but has a collective audience.