The Kuzari, full title Book of Refutation and Proof on Behalf of the Despised Religion ( "Kitâb al-ḥujja wa'l-dalîl fi naṣr al-dîn al-dhalîl"), also known as the Book of the Kuzari, ( "Sefer haKuzari") is one of the most famous works of the medieval Spanish Jewish philosopher and poet Judah Halevi, completed around 1140. Originally written in Arabic, prompted by Halevi's contact with a heretic, probably a Spanish Karaite, it was then translated into Hebrew and is regarded as one the most important apologetic works of Jewish philosophy.