In the Middle Ages, the evangelization of European societies went hand in hand with a growing stigmatization of Jewish populations. Jews were accused of practicing ritual crimes, such as feeding on the blood of Christian children or desecrating hosts.
In the 9th century, Agobard, bishop of Lyon who campaigned for the unity of the Christian world, expressed concern to King Louis the Pious about intellectual competition from Judaism. To understand it, we must look at the writings of Saint Augustine in the 4th century.