David ben Merwan al-Muqammiṣ was one of the first medieval Jews to respond to the philosophical challenge of Muslim rationalism. Nothing about his life is known with any certainty, but he probably flourished in the early years of the tenth century. According to the account given by the tenth-century Karaite historian Kirkisani, David al-Muqammiṣ was a native of Raqqa, in Mesopotamia. Born into the Jewish faith, Kirkisani stated, al-Muqammiṣ became a Christian and then studied philosophy and theology at the well-known school of Nisibis, in Syria. Later, as reported by Kirkisani, he returned to Judaism but is supposed to have made good use of his Christian learning in his commentaries on Genesis and Ecclesiastes, which have been lost. In the latter part of the nineteenth century some quoted fragments of al-Muqammiṣ's philosophical work were discovered...