This mono­graph explores the ways in which eso­teri­cism — the con­scious effort to trans­mit knowl­edge to some peo­ple while hid­ing it from most oth­ers — was used by Jews dur­ing the Mid­dle Ages. While the rab­bis of the Mish­nah and the Midrash felt that cer­tain kinds of knowl­edge were best left unex­plored, medieval savants were caught in a bind. They want­ed des­per­ate­ly to record their thoughts for pos­ter­i­ty, while cor­don­ing them off from unwor­thy eyes. The solu­tion was eso­teri­cism— speech or writ­ing couched in a lan­guage that would be under­stood only by those wor­thy of it. Abra­ham ibn Ezra uti­lized this approach in inter­pret­ing the Bible, as did Mai­monides in his Guide for the Per­plexed. The very first Kab­bal­ist, Rab­bi Isaac the Blind, rep­ri­mand­ed some of his dis­ci­ples for being insuf­fi­cient­ly dis­creet in explain­ing his secrets. His fol­low­ers respond­ed in dif­fer­ent ways — Nah­manides gave only the vaguest hints of kab­bal­is­tic secrets in his Bible com­men­tary while Isaac’s nephew, Ash­er ben David, expound­ed them quite clearly. 

Hal­ber­tal explains com­plex issues clear­ly and grace­ful­ly, mov­ing smooth­ly from dense kab­bal­is­tic pas­sages to abstruse texts of medieval phi­los­o­phy in a way that allows the unspe­cial­ized read­er to fol­low his train of thought with­out plumb­ing the depths of each the­o­log­i­cal sys­tem to which he refers.