Race is a social relationship between people recognizably different in skin color. Recognizability is a necessary element of the relation, but the social aspects of prejudice, exploitation and segregation are the things race is really about. Race has no legitimacy as a biological division of mankind.
Race relations today are a residue of relations between white masters and black slaves. The fact that slaves were black and masters were white was an accident of history. Light skinned Europeans enslaved dark skinned Africans. Europeans had learned about gunpowder from the Chinese and had guns. The Africans didn’t. Skin color was a fact of life that differed between these people. That difference had an ancient and interesting origin, but did not have anything to do with the ability of Europeans to enslave Africans....
The basic change in race ideology that took place at the end of the eighteenth century was to transform the slave who was socially inferior by virtue of enslavement, and was incidentally black, into a person who was inferior because he was black and hence only fitted for slavery….
Why, after three hundred years of slavery did a race theory finally appear? Several things came together. The French Revolution did not just declare that people had personal rights by nature, but that reason ought to hold sway over blind faith. The Age of Reason had been born, and a scientific, and secular, rationale was needed to justify the enslavement of people.
Furthermore, opposition to slavery was beginning to occur. Slave revolts began to give slave masters cause for concern, not to speak of the nascent abolitionist movement. The hypocrisy of the U.S. Constitution which was based on the ideal of human liberty, but recognized the legitimacy of slavery, could be counteracted by the contention that slaves were not quite human, but some sort of inferior race. This was the social basis for the appearance of race ideology as a scientific discipline.
—Richard Fraser, The Struggle Against Slavery in the United States