Let’s assume that the exegetical pay-off of Rom. 9-11 is that all biological descendents of Abraham are irrevocably elect (this is disputed, of course, but it increasingly seems to be the majority reading). This has an interesting theological pay-off that seems to have gone relatively unnoticed: according to Paul, the only individuals in the world whose salvation is not at all in doubt are the Jews. They are bound, by virtue of heredity, to the City of God.
This raises interesting questions, though, about the fate of un-believing (“secular”) Jews, who either actively seek to abandon the people of God, or who view the question with apathetic indifference. In the case of Gentiles, we would have to say that such behavior surely imperils one’s soul, but on the irrevocable election reading of Romans 9-11, not so for Jews. The secular Jew, we must rather say, is a living testament to the irresistibility of election and the perseverance of the saints.
This, for Christians at least, has to be part of the theological significance of the continuing synagogue.