Come, then, let us speak to-day what remains. What is it then that is now required? Why Joseph’s genealogy is traced, who had no part in the birth. And one cause we have mentioned already; but it is necessary to mention likewise the other, that which is more mystical and secret than the first. What then is this? He would not that it should be manifest to the Jews, at the time of the birth, that Christ was born of a virgin.