In the ninth century, Ḥiwi al-Balkhi challenged the fundamentals of Jewish belief with 200 questions and objections which became an important document of rationalist criticism in the intellectual history of Judaism. This chapter deals with Ḥiwi’s criticism of Jewish tradition and its reception. It will be demonstrated that Ḥiwi’s questions and arguments deny not only the authority of the Bible but also of rabbinic exegesis. Moreover, it will be argued that Ḥiwi’s criticism became a crucial impetus for the reinterpretation of Jewish tradition undertaken by his main opponent, Saadia Gaon, in his Book of Beliefs and Opinions. In terms of reception, Ḥiwi’s criticism of tradition in the end became part of Jewish tradition itself.