Translated from the Arabic, with introduction, notes, and appendix, containing the history of the Khazars. Biographical note on Judah Hallevi and map of the Khazar kingdom. The leading apologetic work written in defense of the religious teachings and practices of Judaism. Contents of Al-Khazari: Skeptical reception of the Rabbi - apologetical character of the Book; Divine attributes - laws of purity - the Hebrew language; Refutation of Karaism, survey of Rabbinic attitudes; Tetragrammaton and names of God - contents and criticism of the "Book of Creation"; Criticisms of speculative theology - abstract of Avicenna's psychology - human free will - ethical and social codes - emigration to Palestine.