Browsing in a dictionary, I came upon this biographical entry:
Ha-Levi, Judah (c.1075-1141). Spanish Jewish philosopher and poet. Born in Toledo he studied biblical and rabbinical literature as well as philosophy. His poetry introduces Arabic forms into Hebrew religious expression. He was travelling to Jerusalem on a pilgrimage when he died. His most important philosophical work is Kazari: The Book of Proof and Argument of the Despised Faith, which purports to be a discussion of a Christian, a Muslim and a Jew, each offering the king of the Khazars (in southern Russia) reasons for adopting his faith.
A glimpse of a fascinating life. And a reminder of how intertwined (yet still competitive) the three great monotheistic faiths were in Spain.