The Scientific Revolution and the political and religious conflicts of the late seventeenth century were not the only developments that influenced European thinkers. Europeans’ increased interactions with non-European peoples and cultures also helped produce the Enlightenment spirit. In the wake of the great discoveries of the fifteenth and sixteenth centuries, the rapidly growing travel literature taught Europeans that the peoples of China, India, Africa, and the Americas had very different beliefs and customs. Educated Europeans began to look at truth and morality in relative, rather than absolute, terms.

The powerful and advanced nations of Asia were obvious sources of comparison with the West. During the eighteenth century Enlightenment opinion on China was divided. Voltaire and some other philosophes revered China — without ever visiting or seriously studying it — as an ancient culture replete with wisdom and learning, ruled by benevolent absolutist monarchs. They enthusiastically embraced Confucianism as a natural religion in which universal moral truths were uncovered by reason. By contrast, Montesquieu and Diderot criticized China as a despotic land ruled by fear.

Attitudes toward Islam and the Muslim world were similarly mixed. As the Ottoman military threat receded at the end of the seventeenth century, some Enlightenment thinkers assessed Islam favorably. Others, including Spinoza, saw Islamic culture as superstitious and favorable to despotism. In most cases, writing about Islam and Muslim cultures served primarily as a means to reflect on Western values and practices.

One writer with considerable personal experience in a Muslim country was Lady Mary Wortley Montagu, wife of the English ambassador to the Ottoman Empire. Her letters challenged prevailing ideas by depicting Turkish people as sympathetic and civilized. Montagu also disputed the notion that women were oppressed in Ottoman society.

Apart from debates about Asian and Muslim lands, the “discovery” of the New World and subsequent explorations in the Pacific Ocean also destabilized existing norms and values in Europe. One popular idea, among Rousseau and others, was that indigenous peoples of the Americas were living examples of “natural man,” who embodied the essential goodness of humanity uncorrupted by decadent society.

As scientists developed taxonomies of plant and animal species in response to discoveries in the Americas, they also began to classify humans into hierarchically ordered “races” and to speculate on the origins of such races. The French naturalist Georges-Louis Leclerc, comte de Buffon (1707–1788), argued that humans originated with one species that then developed into distinct races due largely to climatic conditions.

Using the word race to designate biologically distinct groups of humans was new in European thought. Previously, Europeans had grouped other peoples into “nations” based on their historical, political, and cultural affiliations, rather than on supposedly innate physical differences. Unsurprisingly, when 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. The new idea that racial difference was physical and innate rather than cultural 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 by depicting Africans as belonging to a biologically inferior race that was naturally fit for enslavement.

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. Former slaves, like Olaudah Equiano (see Chapter 20) 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. More often, Enlightenment thinkers, Thomas Jefferson among them, supported racial inequality.