According to the account in the Book of Exodus, God addresses the children of Israel as they stand before Mt. Sinai with the words, "You shall be to me a kingdom of priests and a holy nation" (19:6). The sentence, Martha Himmelfarb observes, is paradoxical, for priests are by definition a minority, yet the meaning in context is clear: the entire people is holy. The words also point to some significant tensions in the biblical understanding of the...