East Syriac author Eliya (or Elias) of Nisibis, also known in Syriac as Eliya bar Shinaya, (975-1046), who wrote in both Arabic and Syriac, was Metropolitan of Nisibis from the beginning of the eleventh century. Among other works, a Chronography (in Arabic and Syriac) and dictionary survive. This work, the author’s (a student of Nöldeke) doctoral dissertation, presents in German translation Eliya’s Book of the Proof of the Correct Faith, a polemical work with chapters against Muslims, Jews, Melkites, and Syrian Orthodox Christians. Any reader concerned with religion in the middle east in the eleventh or surrounding centuries, including the varieties of Christianity and also Islam and Judaism, as well as students of Christian Arabic literature, will welcome the reappearance of this translation.