During the medieval period, Jews were increasly pressured to convert. If they gave in and were baptized, these new Christians were to abandon all Jewish practices. Despite the danger in doing so, some Jews did not react indolently while fellow Jews considered or underwent conversion to Christianity. Were these individuals to relapse and return to Judaism, they as well as those who helped them faced the possibility of severe punishment, including death.
Jewish habitation in France was illegal from 1306 through 1315 and again from 1322 until 1359. During these intervening years, many Jews may have converted to Christianity to remain in their homes. It is quite likely that once the periods of unlawful residence had passed, they may have returned to Judaism openly. The idea that Jewish converts to Christianity were returning to Judaism was common to Christian writers.
They believed that they were being activey assisted by Jews to bring about their return to Judaism. As Bernard Gui described, these relapsed converts were returning to the “vomit” of Judaism. These relapsed converts were referred to as “relapsed” regardless of whether they were voluntary converts or had converted under duress. Those Jews who were assisting relapsed converts to return to Judaism were guilty of rejudaizing and were answerable to the Inquisition. While there was no centralized Inquisition during the Middle Ages, there were local tribunals and episcopal Inquisitors. Regarding the assistance Jews extended to relapsed converts, Gui wrote:
“The perfidious Jews attempt, when and wherever they can, secretly to pervert Christians and to attract them to the Jewish perfidy. They do it particularly in the case of those who had been Jews, but were converted and accepted baptism and the Christian faith; and most especially those related to them by marriage or blood. It is ordained however, that the procedure against Christians going over or returning to the Jews’ rite- the latter even if baptized as infants or through the fear of death but not under absolute and positive force- shall be the same as heretics, whether they themselves confess or are convicted, through [the testimony of] Christians or Jews. Their patrons, receivers, and defenders, too, are to be treated on a par with such abettors of heretics.”
In 1321, Bernard Gui in his inquisitorial manual Practica oficii inquisitionis heretice pravitatis, asserted that Jews actively wanted to rejudaize Jewish converts to Chrsitianity. They did so secretly and from Gui’s perspective threatened the Church and Christian society by doing so. This supposed threat would direct part of the inquisitor’s attention to this issue. With his manual, Gui attempted to provide inquisitors with the tools and guidelines for identifying judaizers and the relapsers.
Clement IV’s bull titled Turbato corde in 1267 had already defined (re)judaizing as heresy. Gui considered all Jews as a potential threat to the Church as evidenced by the fact that they blasphemed Christians in their liturgy. They also held blasphemous views on Jesus and Mary. While all Jews posed a threat, those judaizers were “fautores”i.e. supporters of heresy, directly encouraging the convert to relapse or indirectly by simply contacting him or her.
Gui’s account of reversion to Judaism in his Practica was also bolstered by other fourteenth century inquisitors who tried cases of judaizing and relapse. The inquisitional records of Gui in 1317 discuss the case of Johannes de Bretz. Johannes was from Toulouse and converted to Christianity. He lived as a Christian for three years. He then fled to Lerida where he underwent a rejudaizing ritual. The local authorities learned of the situation and deported him to Toulouse. There he refused to recant and return to Judaism. As a result, he was sentenced by Gui to life imprisonment. The same year, Gui would also try another relapsed Jew. This trial was posthumous, however. The case involved the case of another individual also named Johannes (his name was Josse when a Jew). He had relapsed to Judaism and when confronted with his relapse refused to recant. His body was exhumed and burned.
In 1320, Bishop Jacques Fournier of Pamiers tried a case of a convert relapsing to Judaism. This convert claimed his conversion had been forced. Baruch, the German Jew in question, was Toulouse and related that he had been attacked by the “Pastoureaux.” Members of this group were being tried in Toulouse for having killed one hundred and fifty Jews at Castel Sarassin. The accused had been set free by bystanders as they were being escorted to the Narbonne Fort. Upon their freedom they ransacked the Jewish quarter. During the violence, a group of peasants burst into the room where Baruch had been studying and required that he either convert or be killed.
Baruch faced with the choice, aceded to conversion. A Christian friend advised him to go to Pamiers so he could resume his Jewish practice. Baruch testified to the existence of a procedure to converted Jews returning to Judaism but explained that since his conversion was under duress, there was no need for such a procedure. He did so, but was arrested by the Inquisition on the charge of relapsing to Judaism. His argument was unconvincing. Because Baruch had not “protested by word or deed or shown a contrary will, by resisting, that he did not want to be baptized.” They inquisitors of course failed to admit that any such protestation would have likely resulted in Baruch’s death. Consequently, Fournier refused to declare the baptism invalid.
Fourier argued that only total coercion made the sacrament of baptism invalid. This was despite the fact that Baruch had told him that his captors told him that if he protested it would have meant certain death. Left with no other options, Baruch opted to confess his guilt. Once again he abjured Judaism. The two other cases discussed are not recorded as having been forced. While some Jews may have reacted negatively to converts, it appears that many Jews actively helped and even pressured some apostates return the Jewish community.
 Salo Wittmayer Baron, A Social and the Religious History of the Jews: Volume XIII (Philadelphia: Jewish Publication Society, 1969), p.9.
 Kristine T. Utterback, “Conversi-Revert: Voluntary and Forced Return to Judaism in the Early Fourteenth Century,” Church History, Vol. 64. No. 1 (1995): 17.
 Kristine T. Utterback, “Conversi-Revert: Voluntary and Forced Return to Judaism in the Early Fourteenth Century,” Church History, Vol. 64. No. 1 (1995): 18.