To his two major histories of ideas about slavery, The Problem of Slavery in Western Culture and The Problem of Slavery in the Age of Revolution, Yale historian Davis adds an independent, complementary study--anticipating his third volume, The Problem of Slavery in the Age of Emancipation--of what he calls, tellingly, ""the momentous shift from 'progressive' enslavement to 'progressive' emancipation."" Built into that formulation are changes in the idea of progress--social and moral progress. (Slavery's role in economic progress, much disputed by historians, is secondary to Davis--but his findings bear on the issues.) In his first section, ""How 'Progress' Led to European Enslavement of Africans,"" Davis traces the expansion of slavery in company with commercial and imperial expansion--from the Muslims, to the Mediterranean peoples, to the 17th-and 18th-century mercantile powers. These societies, he stresses, were the great innovators and carriers of civilization (but ""slaves themselves were often indispensable carriers of technical and even managerial skills""). How was it, then, that slavery, ""generally accepted to be a necessary and 'progressive' institution"" until the 1760s, in cosmpolitan centers far removed from plantation agriculture, came shortly to be seen as ""the uneconomical vestige of a barbarous age""? This brings Davis' crucial argument--in Part II, ""Redeeming Christianity's Reputation""--that, in self-defense against Enlightenment strictures, British evangelicals embraced and propounded abolitionism (after the 1791 Haitian revolution, as a safeguard against disorder); that abolition appealed to 19th-century liberals as proof that ""public virtue and enlightenment could keep pace with material advance."" The final, ironic twist comes in Part III, ""Abolishing Slavery and Civilizing the World,"" where Davis shows that, in their zeal to wipe out African slavery, the British subjugated Africa (and in their world-crusade, disrupted the world). These intricate and subtle arguments are pursued through myriad concrete examples and close, precise analysis. ""Along with the rosy picture of humanitarian accomplishments, the colonial nations presented excuses for the persistence of 'domestic slavery' and the necessity of certain forms of compulsory labor."" Davis doesn't polemicize, he sees ideology as a force. With a work of such scope and originality, so many scholarly and historical subthemes (among the latter, the role of the Jews, the character of Cuban and Brazilian abolitionism), there are bound to be objections. But Davis has moved the discussion of both slavery and progress to fertile new ground.