The early founding Church fathers came up with an interesting justification for the 'continuing existence' of Jews, now that Christianity had come along. 'Doctrine of the Witness'.
Augustine and the other Church Fathers wrestled with this question of why Judaism continued if it had apparently lost its purpose? Augustine’s answer lay in the “Doctrine of the Witness.” This doctrine suggested that the continuing physical presence of the Jews was desirable because the Jews themselves provided testimony to the truth of Christianity in two ways: First, the Jews possessed Scriptures, thereby proving that Scriptures were no means invented retrospectively by Christians to predict the coming of Jesus…
Secondly, the physical status of the Jews provided testimony to the truth of Christianity. The Jews existed in a subjugated, second-class status as a defeated people…The perpetual servitude of the Jews reminded the world that the Jews are being punished for their rejection of Jesus. Therefore it was desirable that the Jew remain in Christian society. As long as Jews retained their second-class status, they would remind the world of their crime in rejecting Jesus and their validity of Jesus’s teachings…
Although the Jews’ status would always be second-class, the Church Fathers decreed that the Jews must be protected and not eliminated. In this context medieval Christian anti-Semitism provided a protective mechanism against the elimination of the Jews. Or, as Duns Scotus, a thirteenth century Christian theologian, put it, the Jews could be persecuted and virtually eliminated, but some of them would have to be kept alive on a deserted island until the Second Coming.
Prof. Steven Bayme, Understanding Jewish History (pp.120-121):
http://books.google.com/books?id=56QJ9O7MFJ4C&printsec=frontcover&dq=understandine+jewish+history&source=bl&ots=qKHEtqIrjB&sig=DIAxJyBMjpRtbi00JVvON99q-nQ&hl=en&ei=B6_8S_CbMsGZ_Qam08ScBQ&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCYQ6AEwAg#v=onepage&q=doctrine%20of%20the%20witness&f=false
Eh - when was this doctrine changed/abrogated - or is this something that Christians still believe?
(I assume that this is something that is no longer discussed in public and has been now denounced?)
Cheers,
Shafique