Isaiah does not speak of a virgin in the strict sense--merely an unmarried woman. Isaiah is not clear that he is even
speaking to a distant
future conception. The whole meaning of Isaiah's chapter appears to imply that the birth he
prophesies will take place
about 735 B.C. during the reign of King Ahaz the father of the future King Hezekiah.
The words of Isaiah may have literally meant the
conception
of the future King Hezekiah. At the time of Isaiah's
words in
chapter 7, the mother of the future King Hezekiah
would have
been unmarried.
Matthew, on the other hand, under the inspiration of
the
Holy Spirit, creates an interpretation of Isaiah
which is definitely
not literal. Matthew clearly interprets Isaiah in a
fuller sense:
the unmarried woman is the virgin Mary, and
God-with-us is
Jesus.