"What was the Enlightenment? This question has been endlessly debated. In this book, historian Matthew Kadane advances the bold claim that Enlightenment is best defined through what it set out to accomplish, which was nothing short of rethinking the meaning of human nature. Kadane argues that this project centered around the doctrine of original sin and, ultimately, its rejection, signaling the radical notion that an inherently flawed nature can be overcome by human means. Kadane explores these ambitious, wide-ranging themes through the story of the largely unknown Pentecost Barker, an eighteenth-century "purser" and wine merchant. Examining Barker's diary and correspondence with a Unitarian minister, Kadane tracks the transformation of Barker's consciousness from a Puritan to an Enlightenment outlook. In one man's conversion, Kadane tracks large-scale shifts in self-understanding whose philosophical reverberations would (and have continued to) shape debates on human nature for centuries to come"--