Jews living under Christianity--in places like Rome, Worms, Cracow, or, after, 1248, Spain--were subject to two different ruling powers: the church and the state. The following article describes the relationship among these entities in the Middle Ages. It is reprinted with permission from Eli Barnavi's A Historical Atlas of the Jewish People, published by Schocken Books.
It was during the central Middle Ages, between the First Crusade and the Black Death, that the Catholic Church defined its policy towards the Jews. Its attitude was based on the Augustinian doctrine which ascribed an historical mission to the Jews as witnesses to the truth of Christianity. Their existence within Christendom was portrayed as double testimony. As the original recipients of God's messianic prophecies, and despite having rejected them out of blind wickedness, the Jews indirectly attested to the authenticity of these same prophecies. At the same time, their status as a despised nation, living in ignominy and misery, was testimony to God's wrath and to the intervention of Providence, constantly penalizing them for having rejected Christ.
This theological approach implied an acceptance of the continued presence of Jews. Yet many tried to undermine this relatively tolerant leaning. Talmudic texts which stressed the supremacy of the Halakhah [Jewish law], as its decisions were not based on the dubious claim of supernatural inspiration, were exploited by learned [Christian] theologians.
In the twelfth century, Peter Of Cluny (the Venerable) and the instigators of the "trial" against the Talmud in the following century, fulminated against the pretensions of the Jewish Law, denouncing it as an illegitimate, even diabolical, addition to the Scriptures. Post‑biblical Judaism, they said, could be defined as a form of heresy and therefore legitimately extirpated. But the Papacy cut short such ideas. There was no way in which the Church could condemn the Jewish notion of Oral Law and Tradition without compromising its own claim of being the sole interpreter of the Holy Scriptures.
Nevertheless, while it did adhere to the principle of toleration, the Church did not fully exercise its influence to ensure that tolerance was respected in practice. For example, although most popes during twelfth and thirteenth centuries issued bulls prohibiting conversion by force, canon law, by distinguishing between absolute and conditional constraints, did not invalidate conversions obtained by threat. Furthermore, despite papal doubts concerning blood libels, the Church did not restrain the local clergy from spreading such accusations which resulted in the killing of many Jews.