Question

In the trilogy you wrote about the Kuzari’s remarks on the unique quality of Israel, and you wondered where the Kuzari got the idea that only Jews are capable of attaining prophecy..
 
In scholarship, see for example the introduction by Daniel Lasker to Michael Schwarz’s translation of the Kuzari, where they argue that the source is Shi’ite Islam, which attributes a special quality to the Shi’ite imams, and their special quality is expressed through prophecy.