Rabbinic tradition has it that 613 commandments were given to Moses on Mount Sinai, but it does not specify those included in the enumeration. Maimonides methodically and artfully crafts a list of 613 commandments in a work that serves as a prolegemenon to the Mishneh Torah, his monumental code of law. This book explores the surprising way Maimonides put this tradition to use and his possible rationale for using such a tradition. It also explores many of the philosophical and ethical ideas animating the composition of such a list. In the book's second half, Friedberg examines the manner by...