The literary works of ninth-century scholar Dawud al-Muqammas, who converted from Judaism to Christianity and then back to Judaism, reflect his pioneering approaches during a formative time in Jewish and Muslim medieval philosophy. A master of diverse genres, he composed in the ninth century, among other works, the thoughtful Twenty Chapters, which is not only the first known Jewish Kalam text, but also the earliest extant theological summa written in Arabic. This authoritative edition includes the full Judeo-Arabic text in Arabic letter transcription with a facing English translation, as well as an introduction, notes, bibliography, and index.