This chapter focuses exclusively on medieval Jewish civilization, from the fall of the Roman Empire to about 1492. It includes alphabetically organized entries, written by scholars from around the world, include biographies, countries, events, social history, and religious concepts. The legal principle laid down by the talmudic sage Samuel (third cent.) that dina de-malkhuta dina, the law of the kingdom is law, played an important role in medieval Jewish civilization and law. In essence the rule is the halakhic answer to the problem of conflict between Jewish law and Gentile law. The most famous medieval disputation, repeatedly written about but as yet incorrectly understood, was that of Barcelona in 1263. From the beginning of its existence, the Church was always concerned with heresy, and waged relentless campaigns to alter or eradicate beliefs or practices that were contrary to its established doctrines.