If philosophers did not believe the lower classes qualified for enlightenment, how did they regard individuals of different races? In recent years, historians have found in the Scientific Revolution and the Enlightenment a crucial turning point in European ideas about race. A primary catalyst for new ideas about race was the urge to classify nature unleashed by the Scientific Revolution’s insistence on careful empirical observation. In The System of Nature (1735), Swedish botanist Carl von Linné argued that nature was organized into a God-given hierarchy. As scientists developed taxonomies of plant and animal species, they also began to classify humans into hierarchically ordered “races” and to investigate the origins of race. The comte de Buffon (komt duh buh-FOHN) argued that humans originated with one species that then developed into distinct races due largely to climatic conditions.

Enlightenment thinkers such as David Hume and Immanuel Kant helped popularize these ideas. In Of Natural Characters (1748), Hume wrote:

Kant taught and wrote as much about “anthropology” and “geography” as he did about standard philosophical themes such as logic, metaphysics, and moral philosophy. He elaborated his views about race in On the Different Races of Man (1775), claiming that there were four human races, each of which had derived from an original race. According to Kant, the closest descendants of the original race were the white inhabitants of northern Germany. (Scientists now believe the human race originated in Africa.)

Using the word race to designate biologically distinct groups of humans, akin to distinct animal species, was new. Previously, Europeans grouped other peoples into “nations” based on their historical, political, and cultural affiliations, rather than on supposedly innate physical differences. Unsurprisingly, when European thinkers drew up a hierarchical classification of human species, their own “race” was placed at the top. Europeans had long believed they were culturally superior to “barbaric” peoples in Africa and, since 1492, the New World. Now emerging ideas about racial difference taught them they were biologically superior as well. In turn, scientific racism helped legitimate and justify the tremendous growth of slavery that occurred during the eighteenth century. If one “race” of humans was fundamentally different and inferior, its members could be seen as particularly fit for enslavement and liable to benefit from tutelage by the superior race.

Racist ideas did not go unchallenged. The abbé Raynal’s History of the Two Indies (1770) fiercely attacked slavery and the abuses of European colonization. Encyclopedia editor Denis Diderot adopted Montesquieu’s technique of criticizing European attitudes through the voice of outsiders in his dialogue between Tahitian villagers and their European visitors. (See “Primary Source 16.5: Denis Diderot, ‘Supplement to Bougainville’s Voyage.’”) Scottish philosopher James Beattie (1735–1803) responded directly to claims of white superiority by pointing out that Europeans had started out as savage as nonwhites supposedly were and that many non-European peoples in the Americas, Asia, and Africa had achieved high levels of civilization. Former slaves, like Olaudah Equiano (see “Primary Source 17.4: Olaudah Equiano’s Economic Arguments for Ending Slavery” in Chapter 17) and Ottobah Cugoana, published eloquent memoirs testifying to the horrors of slavery and the innate equality of all humans. These challenges to racism, however, were in the minority. Many other Enlightenment voices supporting racial inequality — Thomas Jefferson among them — may be found.

Scholars are only at the beginning of efforts to understand the links between Enlightenment thinkers’ ideas about race and their notions of equality, progress, and reason. There are clear parallels, though, between the use of science to propagate racial hierarchies and its use to defend social inequalities between men and women. French philosopher Jean-Jacques Rousseau used women’s “natural” passivity to argue for their subordinate role in society, just as other thinkers used non-Europeans’ “natural” inferiority to defend slavery and colonial domination. The new powers of science and reason were thus marshaled to imbue traditional stereotypes with the force of natural law.