Divergences among the early thinkers of the Enlightenment show that, while they shared many of the same premises and questions, the answers they found differed widely. The spread of this spirit of inquiry and debate owed a great deal to the work of the philosophes, a group of influential French intellectuals.

To appeal to the public and get around the censors, the philosophes wrote novels and plays, histories and philosophies, and dictionaries and encyclopedias, all filled with satire and double meanings to spread their message. One of the greatest philosophes, the baron de Montesquieu (mahn-tuhs-KYOO) (1689–1755) pioneered this approach in The Persian Letters (1721). This work consists of letters supposedly written by two Persian travelers, Usbek and Rica, who as outsiders see European customs in unique ways and thereby allow Montesquieu a vantage point for criticizing existing practices and beliefs.

Disturbed by the growth in royal power under Louis XIV and inspired by the example of the physical sciences, Montesquieu set out to apply the critical method to the problem of government in The Spirit of Laws (1748). Arguing that forms of governments were shaped by history, geography, and customs, Montesquieu identified three main types: monarchies, republics, and despotisms. A great admirer of the English parliamentary system, Montesquieu argued for a separation of powers, with political power divided among different classes and legal estates holding unequal rights and privileges. Decades later, his theory of separation of powers had a great impact on the constitutions of the United States in 1789 and of France in 1791.

The most famous philosophe was François-Marie Arouet, known by the pen name Voltaire (1694–1778). Early in his career he was arrested twice for insulting noblemen. To avoid a prison term, Voltaire moved to England for three years, and there he came to share Montesquieu’s enthusiasm for English liberties and institutions.

Returning to France, Voltaire met Gabrielle-Emilie Le Tonnelier de Breteuil, marquise du Châtelet (1706–1749), a gifted noblewoman. Madame du Châtelet invited Voltaire to live in her country house at Cirey in Lorraine. Passionate about science, she studied physics and mathematics and published the first French translation of Newton’s Principia.

While living at Cirey, Voltaire wrote works praising England and popularizing English scientific progress. Yet, like almost all the philosophes, Voltaire was a reformer, not a revolutionary. He pessimistically concluded that the best form of government was a good monarch, since human beings “are very rarely worthy to govern themselves.” Nor did Voltaire believe in social and economic equality. The only realizable equality, Voltaire thought, was that “by which the citizen only depends on the laws which protect the freedom of the feeble against the ambitions of the strong.”1

Voltaire’s philosophical and religious positions were much more radical. Voltaire believed in God, but he rejected Catholicism in favor of deism, belief in a distant, noninterventionist deity. Above all, Voltaire and most of the philosophes hated religious intolerance, which they believed led to fanaticism and cruelty.

The strength of the philosophes lay in their number, dedication, and organization. Their greatest achievement was a group effort — the seventeen-volume Encyclopedia: The Rational Dictionary of the Sciences, the Arts, and the Crafts, edited by Denis Diderot (1713–1784) and Jean le Rond d’Alembert (1717–1783). Completed in 1765 despite opposition from the French state and the Catholic Church, the Encyclopedia contained hundreds of thousands of articles by leading scientists, writers, skilled workers, and progressive priests. Science and the industrial arts were exalted, religion and immortality questioned. Intolerance, legal injustice, and out-of-date social institutions were openly criticized.

After about 1770 a number of thinkers and writers began to attack the philosophes’ faith in reason and progress. The most famous of these was the Swiss intellectual Jean-Jacques Rousseau (1712–1778). Like other Enlightenment thinkers, Rousseau was passionately committed to individual freedom. Unlike them, however, he attacked rationalism and civilization as destroying, rather than liberating, the individual. Warm, spontaneous feeling, Rousseau believed, had to complement and correct cold intellect. Rousseau’s ideals greatly influenced the early romantic movement, which rebelled against the culture of the Enlightenment in the late eighteenth century.

Rousseau also called for a rigid division of gender roles, arguing that women and men were radically different beings. According to Rousseau, because women were destined by nature to assume a passive role in sexual relations, they should also be passive in social life and devote themselves to taking care of their husbands and children. Additionally, he believed that women’s love for displaying themselves in public, attending salons, and pulling the strings of power was unnatural and had a corrupting effect on both politics and society.

Rousseau’s contribution to political theory in The Social Contract (1762) was based on two fundamental concepts: the general will and popular sovereignty. According to Rousseau, the general will is sacred and absolute, reflecting the common interests of all people, who have displaced the monarch as the holder of sovereign power. The general will is not necessarily the will of the majority, however. At times the general will may be the authentic, long-term needs of the people as correctly interpreted by a farseeing minority.