A World of Piety examines the historical aspirations of kabbalah to prompt a revival of ancient rabbinic piety in medieval Castile. What were the aims of the celebrated works of rabbinic wisdom fashioned during the reigns of Alfonso X and Sancho IV of Castile, including the formative Book of the Zohar? In pursuit of this question, Judaica scholar Jeremy Phillip Brown turns to the Hebrew and Aramaic writings composed by Todros ben Joseph ha-Levi Abulafia of Toledo, Joseph Gikatilla of Medinaceli, and especially Moses de Leon of Guadalajara. These writings set out to disseminate the secret patrimony of ancients: a knowledge of divinity comprised of essentially Jewish attributes as a basis for human emulation. According to these texts, God models a pious form of life-not merely a life of Torah and the commandments, but a program exceeding the norms of religious obligation. Midnight vigils for prayer and study, guarding the eyes and tongue,sexual austerity, spiritual poverty and concern for the materially poor-the texts affirm that God exemplifies these and other modes of piety, prompting their imitation as a penitential means of individual and even socialtransformation. Bymeans of their writings, the Castilian authors sought to form penitents as "other people" created anew in the Judeomorphic image of God.A World of Pietysheds light on the core motivations of a discourse that would emerge as a major domain of religion and thought by reconstructing the socio-historical ambitions of a little-known cadre of medieval rabbis active in a Christian milieu.