In this essay, Alan Levine and Darren Staloff describe Enlightenment-era criticisms of the natural law tradition. One group of critics, the “naturalizers,” referred to natural law, but argued that it could be deduced from man’s natural state. For Voltaire, Montaigne, and Diderot, this was grounded in anthropological observations of Native Americans and Tahitians; for the contractarian naturalizers such as Hobbes, Locke, and Rousseau, rights were to be derived from how man would live in the “state of nature.” The second group of critics, the moral reductionists, rejected the prescriptive function of natural law, and based their reductive account of morality on psychological facts. For proponents of Epicureanism, such as Voltaire and Mandeville, the moral code was based on self-love and a desire for happiness and pleasure; for other reductionists – Shaftsbury, Hutcheson, Hume, and Smith – ethical knowledge was a sympathy to be cultivated, not a rational demonstration. Both types of reductionism were relativistic. The final group of critics described in this essay offered a prescriptive replacement of the natural law. For Rousseau the infallible “general will” served as the only source of legitimate authority. Mirabeau and Quesnay sought a descriptive and prescriptive source of normative judgment based on pre-civilized nature. Condillac and his followers, the sensationists, promoted a republican and liberal political order as the only way to achieve mankind’s necessary goals of avoiding pain and fulfilling desires. Enlightenment criticisms of natural law had profound implications for both political theory and practice, and, though the prescriptive replacements for natural law were the least philosophically radical in the intellectual realm, they proved to offer the most revolutionary political agenda in the practical realm, fueling the radical, and often violent, measures of the French Revolution.



Jean-Jacques Rousseau was born in Geneva in 1712. At a young age he was left with only his father, who exposed him to the beginnings of a classical education. When his father was forced to leave Geneva, he was made an apprentice to an engraver at the age of thirteen. He left the position at sixteen and traveled to Annecy, where he met Madame Louise de Warens, who influenced his conversion to Catholicism. Rousseau’s limited childhood education and his relationship with de Warens contributed to a life marked by tumultuous attachments, philosophical writing, and frequent quarrels with other Enlightenment philosophes.

In 1742 Rousseau traveled to Paris to begin composing music. While in Paris, Rousseau met Therese Lavesseur, his long-time companion and future wife; together they had five children, though they left each one at an orphanage. At this time Rousseau began his contact with some of the philosophes, including Diderot and d’Alembert. He contributed articles on music to their Encyclopedie. Rousseau made his debut as an author when his Discourse on the Arts and Sciences won an essay contest in 1750. He sparked controversy by arguing that neither the arts nor the sciences purified morals, but instead contributed to their decline.

Rousseau’s political writings were also widely read and debated. His Discourse on the Origins of Inequality (1753) attributes the corruption of human nature to civilization and social institutions. After a short-term love affair and disputes with some of his philosophe companions, he moved to Montmorrency, where he published The Social Contract, in which he elaborates the concept of general will (first introduced in his second discourse), and Emile, a treatise that offers his views on education. Both of these works led to his condemnation by the government of Paris, and he was forced to flee the city for Switzerland.

In the later part of his life, Rousseau’s writing took a more self-reflective turn. After writing his autobiography Confessions (named after Augustine’s autobiography, written over a thousand years earlier), Rousseau moved to England at the invitation of David Hume in 1776. Fights with Hume caused him to return to the southeast of France the next year. He remained there for three years before returning to Paris, where he spent the final period of his life copying music and writing his last two works, Rousseau: Judge of Jean Jacques, and Reveries of the Solitary Walker. He died in 1778.

To read more about Rousseau’s life and works, please click here.


Voltaire was born Francois Marie d’Arouet in France in 1694. As the child of wealthy, educated, aristocratic parents, he received a rigorous Jesuit education. In the early 1720s, Voltaire repeatedly rejected the legal career pushed on him by his father. Instead, he pursued patronage for his literary aspirations, and quickly emerged as an intelligent wit (and a libertine) in France’s elite literary circles.

After a scandal in which Voltaire was accused of defaming another aristocrat, he spent three years in England, from 1726-1729. During this time he encountered the work of Locke and the English Newtonians through Lord Bolingbroke. Though Bolingbroke drew Voltaire to the Tory intellectual scene, Voltaire also encountered the Whigs through another contact, Everard Fawkener. Some of Voltaire’s later work was inspired by his encounter with the new literary genre exemplified by Jonathan Swift’s Gulliver’s Travels, a combination of narrative and social criticism. 

When Voltaire returned to France, he began a long relationship with Madame Emilie du Chatelet in 1733. A brilliant woman, Chatelet collaborated with Voltaire on many projects until her death in 1749. When the unapproved publication of Voltaire’s Lettres Philosophiques (Philosophical Letters) provoked his exile from France, Voltaire threw himself into debates begun over the work of Newton and Descartes. Out of this effort emerged his Elements de la philosophie de Newton (Elements of the Philosophy of Newton), first published in 1738 and again in 1745. Chatelet’s support for this work contributed to Voltaire’s new image as a heroic defender of Newtonianism, and therefore true philosophy.

The second half of Voltaire’s life can be characterized as a struggle to preserve his heroic image. In the 1740s he remained closely tied to the aristocracy. He was appointed Royal Historiographer of France in 1745. In the same year, he accepted Frederick the Great of Prussia’s invitation to direct Berlin’s Academy of Sciences. Four years later, he joined Frederick’s court. His years in these positions allowed him to publish one of his most famous works in 1751, Essais sur les moeurs et l’esprit des nations (An Essay on the Manners and Spirit of the Nations). 

Yet despite his rise to fame in these years, another fall from political favor in the 1750s prompted his move in 1759 to his final home at Ferney, between France and Switzerland. Voltaire began to infuse his philosophical writings with social criticism and calls for political reform. His defense of Diderot’s Encyclopedie, supported by his own Dictionnaire philosophique (1764-1770), turned into a movement to rally together Enlightenment philosophes as defenders against fanaticism and superstition. Voltaire can be considered crucially responsible for shaping the image of the philosophe as a modern, progressive-minded reformist who sought to liberate the masses from traditional authority. In 1778, he spent the final weeks of his life as a sick man but a welcome hero in France.

To read more about Voltaire’s life and works, please click here.


affective psychology:

the study of non-rational human emotions


based on the study of humans and human societies

a priori:

“from before”; knowable through reason prior to experience


here, Hobbes, Locke, and Rousseau; those who believed that a government can only be legitimately formed by a social contract which rests on the consent of its citizens


the field concerned with the structure of the universe

Diderot, Denis:

(1713 – 1784) a French philosopher and writer, who co-founded the Encyclopedie


discovered or verifiable by observation or experiment


of, or relating to, epistemology, or the philosophy of knowledge and belief


a philosophy which treats pleasure as the highest good

Hobbes, Thomas:

(1588 – 1716) a political philosopher whose most famous book, Leviathan, introduces and relies on social contract theory. For more information on Thomas Hobbes and his relationship to the natural law tradition, please see the section of this website on “Thomas Hobbes: From Classical Natural Law to Modern Natural Rights.”


also called sensationists; a group including Helvetius, Condorcet, Cabanis, and Tracy, heavily influenced by Condillac. They called for a republican and liberal political order, that man might better avoid pain and fulfill his desires.

Mandeville, Bernard de:

(1670 – 1733) an English philosopher, satirist, and political economist, he authored The Fable of the Bees, which features the poem “The Grumbling Hive.”


relating to the philosophy of materialism, which holds that physical matter is the only or fundamental reality and that all being and processes can be explained as manifestations of or results from matter


related to the nature of being

Montaigne, Lord Michel Eyquem de:

(1533 – 1592) a famously skeptical French essayist, philosopher, and statesman


relating to how things should be


a philosophy that viewed pre-civilized nature as the ultimate source of normative judgment, and advocated a liberal, laissez-faire economic system to maximize agricultural productivity


providing a rule to be followed

Rochefoucauld, François de La:

(1613 – 1680) a French author of maxims and memoirs who viewed self-interest as the primary human motive

Rousseau, Jean-Jacques:

(1712 – 1778) a contractarian philosopher and writer, whose beliefs were influential in the French and American revolutions

Saint-Evremond, Charles de:

(1610 – 1703) a French essayist, literary critic, and hedonist

 “state of nature”:

the hypothetical condition for men prior to the formation of societies. During the Enlightenment, “state of nature” arguments were employed to criticize the natural law and to argue for natural rights.

Voltaire, or Francois-Marie Arouet:

(1694 – 1778) a French writer and philosopher who advocated social reform


I.  Introduction

A. natural law important for many Enlightenment thinkers, like Grotius, Locke, and Pufendorf in the 17th century, and Vattel and Burlamaqui in the 18th

  1. natural law revealed by reason, provided a universal pre-political standard for human action

B.  other thinkers reframed or eliminated natural law as a prescriptive guide, caused by

  1. suspicion of traditional account, due to perceived susceptibility to abuse
  2. undermining of Christianity, due to discovery of the New World
  3. new Lockean view of reason as purely calculative, which cast doubt upon the possibility of rationally knowable universal moral principles

II. Critics: “Naturalizers”

A. Voltaire, Diderot, and precursors (e.g. Montaigne) referred to natural law, but argued that it could be deduced from hypothetical accounts of humankind in its original state, grounded in anthropological observations

1. natural law as maxims, not the command of reason

2. viewed the natural, “pure” standard of human behavior as the pre-civilized state

3. critiqued class system, called for hedonism, enjoyment of simple pleasures, and liberal political institutions

B. contractarians (Hobbes, Locke, and Rousseau) talk about a “state of nature”

C. Montaigne and Voltaire argue from observations of Native Americans, Diderot, of Tahitians

III. Critics: Moral Reductionists

A. rejected prescriptive function of natural law, instead offered a reductive account of morality, based on extra-rational facts of human psychology; criticized how social and political practices violated principles and purposes

B. Epicureanism

1. based its moral code on self-love (amour-propre)

2. Voltaire and Mandeville argue that moral judgments are grounded in a desire for happiness and pleasure

3. a relativistic moral science, arguing that forms of government, law, and morality most conducive to happiness will vary by the custom, conventions of different societies

C. another strain of reductionism, prevalent within the Scottish enlightenment, based on rational self-interest

1. Shaftsbury treats ethical knowledge as the cultivation of innate moral sense, not a rational demonstration

a) amplified by Hutcheson, Hume, and Smith, who describe morality as issuing from instinctive sympathy for fellow creatures

b) sought to maximize human happiness and public utility via political wisdom and moral truth

c) morality from the heart, not the head

d) also relativistic

IV. Critics: Prescriptive Replacements of Natural Law

A. more radical; denied natural law, replaced it with prescriptive power

1. Rousseau embraced infallible “general will” as universal source of legitimate authority

a) knowable, binding, and rooted in empirically given realities

b) philosophy aided in the French Revolution

2. Mirabeau and Quesnay

a) sought descriptive and prescriptive source of normative judgment, turned to pre-civilized nature

b) led to a liberal, laissez-faire model of economic policy to maximize agricultural productivity

3. Condillac and sensationists or “Ideologues”

a) Helvetius, Condorcet, Cabanis, Tracy

i. metaphysical analysis and materialist reading of human sensibility suggested that mankind necessarily sought to avoid pain and fulfill its desires and wills, universally

ii. a broadly republican and liberal political order as the sole way to achieve these goals.

V. Conclusion

A. Enlightenment critic’s thought had profound implications for political theory and practice in the 18th century

  1. Non-prescriptive reductionism most radical in theory, but least radical practically
  2. Strategy of prescriptive replacements for natural law least radical in theory, but most revolutionary practically, fuelling radical and violent measures of French Revolution.

Part I. Basic Interpretation of Enlightenment Critics of the Natural Law

If you are interested, after reading Alan Levine and Darren Staloff’s essay, in learning more about the Enlightenment critics of natural law, please go to the Primary Source Documents to read works by Mandeville, Hume, Montaigne, and Voltaire. As you go back to the primary sources, consider the following questions:

  1. What role did Christianity play in enlightenment criticisms of natural law? Which intellectual trends and historical events contributed to these criticisms?
  2. How do the “naturalizers” differ from the moral reductionists? What distinguishes them from what the essay authors describe as “the most radical theorists who proposed entirely new moral theories that were just as if not more prescriptive than traditional natural law theory”?
  3. What is the “state of nature”? How does the theory of the state of nature contribute to the reconception and eventual elimination of natural law as a prescriptive guide for human action?
  4. What motivates the different Enlightenment critics? What methods did the different thinkers employ to figure out what is true?
  5. What were the political effects of Enlightenment-era criticisms of natural law?

Part II. Connections to Other Thinkers

In order to better understand the Enlightenment-era critics of the natural law, it is important to compare their views with those of other important thinkers within the natural law tradition. As you learn more about the Enlightenment critics of natural law, consider how their thought interacts with the ideas of earlier and later thinkers.

  1. In “Of Cannibals” Montaigne writes: “They are savages at the same rate that we say fruits are wild, which nature produces of herself and by her own ordinary progress; whereas, in truth, we ought rather to call those wild whose natures we have changed by our artifice and diverted from the common order.” How does Montaigne’s view of “the common order” differ from Aquinas’? How does each thinker believe this order can best be maintained or cultivated? What differences does this reveal in their view of human nature, and the relationship between man and society?
  2. Naturalists like Montaigne claimed to base their philosophies in part on empirical anthropological observations. Aristotle also claimed his philosophy to be based on observation of human nature. Are the naturalists more accurate? More scientific? Are there essential differences in what each consider to be relevant data for consideration?
  3. Levine and Staloff write that “an awareness of the importance of wealth, power, and commercial prosperity for the happiness of a nation led [Mandeville] to insist that private vices were in fact public benefits if prudently regulated.” Older natural law thinkers like Aristotle and Aquinas did not see a conflict between the public good and the private good, for each good was considered to be necessary for the other. Can the private and public good ever conflict? And if so, is there a way to weigh one against another? If they can’t be weighed against one another, how should decisions be made about whether to act for the public or private good?
  4. In “Of the Origin of Government,” David Hume argues that government encourages good behavior because “our duty to the magistrate is more strictly guarded by the principles of human nature, than our duty to our fellow-citizens.” At first glance, this appears similar to Aquinas’ justification of the law in Question 95 of the Summa Theologiae. Yet unlike Aquinas, Hume did not believe the government capable of reforming men, for he did not believe men capable of reform. How might one evaluate which view is more reasonable? Could a Thomistic view, by treating man as free and capable of reform, alleviate the tension that Hume identifies between authority and liberty? How did the American Founders address this issue?
  5. Contemporary advocates of “sustainable development” often display a type of primitivism in their desire to preserve pre-industrialized societies. But when industrialization does occur in these societies, it is in accordance with Mandeville’s model: the society is made wealthier and more productive through a process which involves a loss of cultural traditions at an individual level. Which Enlightenment-era philosophy provides a better model: primitivism, or Mandeville’s system? How can a decision about this be reached? And what does the conclusion suggest about industrialization? Can either of these philosophies resolve the issue? Why or why not?

Part III. Critical Interpretation of Enlightenment Critics of Natural Law

Given a basic understanding of the Enlightenment-era critics, examine their arguments more critically. Are they persuasive? What further implications do they have? Use the questions below as your guide.

  1. Why do the naturalists make normative claims based on descriptions of pre-civilized man? What are the differences between pre-civilized man, and people living in society today? Why would it be desirable for people living in society to adopt pre-social-contract forms of action? Aren’t the two modes of existence inherently incompatible? What arguments can you find for negotiating this tension?
  2. Rousseau believed the “general will” to be empirically knowable and binding. How might the “general will” be known empirically? And what would make it binding? Is it possible for the “general will” to reject itself as the basis for legitimacy? If so, what would occur?
  3. Levine and Staloff write, “Thinkers like Voltaire and Mandeville insisted that moral judgment was grounded in the universal desire for happiness and pleasure, and that the public good was the socially useful, just as the private good was whatever resulted in individual happiness. Unlike natural law theory, such a moral science was relativistic: it argued that the measures and forms of government, law, and morality most likely to result in happiness varied by custom, convention, and mores.” Look at Mandeville’s “The Grumbling Hive.” What sort of vision of happiness is presented there? How does Mandeville justify it as the right thing for government to seek?
  4. Many Enlightenment-era criticisms of the natural law are based on a claim that the natural law is not rationally knowable. Instead, its critics propose alternative bases for normativity. Do any of these succeed in providing compelling reasons why things should be one way, and not another?
  5. According to Levine and Staloff, moral reductivism “could not issue normative commands from on high. It could, however, clarify moral and political principles and purposes and show how their application might be maximized.” Examine Hume’s “On the Origin of Government.” In it, how does he clarify the relevant principles and show possible maximizations of their application? Does he rely on normative assumptions? (What things does he assume are good or bad? In need of remedy?) Evaluate his method. Where might it lead with time? Is it only useful to move from assumptions to the appropriate conclusions?