Until recently, peoples of every race and continent lived in a world in which slavery was an accepted part of the social order. Europeans did not outdo others in enslaving people or in treating slaves viciously. They outdid others by creating a Christian civilization that eventually stirred moral condemnation of slavery and roused mass movements against it. Perception of slavery as morally unacceptable – as sinful – did not become widespread until the second half of the eighteenth century. Slavery, not merely serfdom, existed in Western and Central Europe as late as the Renaissance and in Russia until the mid-nineteenth century.

Neither slavery nor serfdom was racially determined. From ancient times Europeans had recruited slaves without regard to race, and whites overwhelmingly predominated among the millions of slaves held within Europe. When European overseas expansion in the fifteenth century made Africa the principal source of slaves, slavery became identified with racial stratification. Muslims and then Christians entered Africa and carried off enormous numbers, largely sold to them by other Africans. Over time Muslims, too, increasingly identified slave status with blackness, although less rigorously than Christians did. During the next four centuries it was in the vast plantation system of the Americas that both the critique and the defense of slavery came to focus on racial as well as class stratification.