"Why," an exasperated Jonathan Edwards asked, "can't we be contented with. . . the canon of Scripture?" Edwards posed this query to the religious enthusiasts of his own generation, but he could have just as appropriately put it to people across the full expanse of early American history.

In the minds of her critics, Anne Hutchinson's heresies threatened to produce "a new Bible." Ethan Allen insisted that a revelation which spoke to every circumstance of life would require "a Bible of monstrous size." When the African-American prophetess Rebecca Jackson embarked on a spiritual journey...