Ibn ḥazm († 1064) was one of the most original religious thinkers in the cultural history of Islam and the first polemicist from Andalusia to attempt - in his Fisal - to refute the tenets of Judaism and Christianity. This book focuses mainly on his doctrine on the relation between Islam and Christianity in theory and practice. He lived in a society, which was characterised by religious pluralism: Jews, Christians and Muslims lived together in a single community, so that his views can only be understood in the social-political context of his times. The author first discusses the biography of Ibn ḥazm, the question of his Christian origins and personal contacts with Christians as well as the chronology of his oeuvre. He then looks at his evaluation of Christianity, the sources for his treatment, his understanding of Christian doctrine and ritual, and the degree of originality of his treatment, and concludes by examining his influence on later Islamic polemicists. In three appendices the author shows relations between the printed text of al-Fisal and its only manuscript source, MS Vienna 975, presents the texts of the Epistles of Paul from MS National Library Madrid ms 4971 (Novum Testamentum Arabicum) and of the Kitāb 'alā 'l-Tawrāt (MS Köprülü, 794 M. 196 YK) of the later polemicist 'Alā' al-Dīn al-Bājī.