Natural Law in Ethics

Natural Law

Investopedia / Jessica Olah

What Is Natural Law?

Natural law is a theory in ethics and philosophy that says that human beings possess intrinsic values that govern their reasoning and behavior.

Natural law maintains that these rules of right and wrong are inherent in people and are not created by society or court judges.

Key Takeaways

  • The theory of natural law says that humans possess an intrinsic sense of right and wrong that governs our reasoning and behavior.
  • The concepts of natural law stem from the times of Plato and Aristotle and were practiced by great thinkers such as Mahatma Gandhi and Martin Luther King Jr.
  • Natural law is constant throughout time and across the globe because it is based on human nature, not on culture or customs.
  • Natural law is opposed to theories that laws are socially constructed and created by people.
  • Examples of natural laws exist in fields from philosophy to economics.

Understanding Natural Law

Natural law holds that there are universal moral standards that are inherent in humankind throughout all time, and these standards should form the basis of a just society.

Human beings are not taught natural law per se. Instead, we “discover” it by consistently making choices for good instead of evil. Some schools of thought believe that natural law is passed to humans via a divine presence.

Under the theory of natural law, everyone—regardless of their governmental or political system, culture, or religion—has the same rights, and these rights cannot be denied by others. The birthrights granted to humans under natural law, however, are not the same as human rights, which vary and can change depending on societal views. For example, a human right in the United States is equal pay for equal work; however, in other countries, it is not.

Although natural law mainly applies to the realm of ethics and philosophy, it is also used extensively in theoretical economics.

Natural Law vs. Positive Law

The theory of natural law believes that our civil laws should be based on morality, ethics, and what is inherently correct. This is in contrast to what is called "positive law" or "human law," which is defined by statute and common law and may or may not reflect the natural law. 

Examples of positive law include rules such as the speed that individuals are allowed to drive on the highway and the age that individuals can legally purchase alcohol. Ideally, when drafting positive laws, governing bodies would base them on their sense of natural law.

"Natural laws" are inherent in us as human beings. "Positive laws" are created by us in the context of society.

Examples of Natural Law

Examples of natural law abound, but philosophers and theologians throughout history have differed in their interpretations of this doctrine. Theoretically, the precepts of natural law should be constant throughout time and across the globe because natural law is based on human nature, not on culture or customs.

When a child tearfully exclaims, “It’s not fair [that]..." or when viewing a documentary about the suffering of war, we feel pain because we're reminded of the horrors of human evil. And in doing this, we are also providing evidence for the existence of natural law. A well-accepted example of natural law in our society is that it is wrong for one person to kill another person.

Examples of Natural Law in Philosophy and Religion

  • Aristotle (384–322 BCE) is considered by many to be the founder of natural law. He argued that what is “just by nature” is not always the same as what is “just by law.” Aristotle believed that there is a natural justice that is valid everywhere with the same force. This natural justice is positive and does not depend on the decisions or laws of any one group of people.
  • For St. Thomas Aquinas (1224/25–1274 CE), natural law and religion were inextricably connected. He believed that natural law "participates" in the divine "eternal" law. Aquinas thought eternal law to be that rational plan by which all creation is ordered, and natural law is the way that human beings participate in the eternal law. He further posited that the fundamental principle of natural law is that we should do good and avoid evil. 
  • Mahatma Gandhi (1869-1948) argued that humanity is in danger of being destroyed by seven "sins," often called the seven social sins: wealth without work, politics without principle, pleasure without conscience, commerce (or business) without morality (or ethics), knowledge without character, science without humanity, and religion without sacrifice. In each of these cases, the solution to the sin (work, principle, conscience, morality, character, humanity, and sacrifice) is an external standard derived from natural law.
  • Martin Luther King, Jr. (1929–1968) argued that people have an obligation to obey natural laws over unjust positive laws that conflict with them, writing that "One has not only a legal but a moral responsibility to obey just laws. Conversely, one has a moral responsibility to disobey unjust laws... To put it in the terms of St. Thomas Aquinas: An unjust law is a human law that is not rooted in eternal law and natural law. Any law that uplifts human personality is just. Any law that degrades human personality is unjust."

Philosophers of natural law often do not explicitly concern themselves with economic matters; likewise, economists systematically refrain from making explicit moral value judgments. Yet the fact that economics and natural law are intertwined has been borne out consistently in the history of economics.

Natural Law and the U.S. Legal System

To many, natural law is the foundation upon which the U.S. legal system was built. Natural law is witnessed in the country's laws, systems, covenants, and how its citizens live and interact. One of its earliest documents—the Declaration of Independence—asserts that every human is granted unalienable rights to life, liberty, and the pursuit of happiness, and it was that assertion that formed the frame of the United States legal system.

However, many early laws were exclusionary, affording rights only to a few. It took hundreds of years for some inhabitants to be considered legally human and even longer for them to be afforded the same unalienable rights as inscribed by Thomas Jefferson.

Over time, the moral push of activists and natural law proponents led to the ratification of some laws and the enactment of others, such as the Civil Rights Act, to blanket every human with the ability to exercise these rights and freedoms.

Examples of Natural Law In Economics 

Because natural law as an ethical theory can be understood to be an extension of scientific and rational inquiry into how the world works, the laws of economics can be understood as natural laws of how economies “should” operate. Moreover, to the extent that economic analysis is used to prescribe (or proscribe) public policy or how businesses ought to conduct themselves, the practice of applied economics must rely at least implicitly on some ethical assumptions:

  • Early economists of the medieval period, including Thomas Aquinas and the Scholastic monks of the School of Salamanca, heavily emphasized natural law as an aspect of economics in their theories of the just price of an economic good. 
  • John Locke based his theories related to economics on a version of natural law, arguing that people have a natural right to claim unowned resources and land as private property, thereby transforming them into economic goods by mixing them with their labor. 
  • Adam Smith (1723–1790) is renowned as the founder of modern economics. In Smith's first major treatise, "The Theory of Moral Sentiments," he described a "system of natural liberty" as being the matrix of true wealth. Many of Smith's ideas are still taught today, including his three natural laws of economics:
  1. The Law of Self-Interest: People work for their own good.
  2. The Law of Competition: Competition forces people to make a better product.
  3. The Law of Supply and Demand: Enough goods would be produced at the lowest possible price to meet demand in a market economy.

What Is the Theory of Natural Law?

Natural law is a theory of ethics that says that human beings possess intrinsic values that govern our reasoning and behavior. It states that there are universal moral standards that are seen across time periods and societies because these standards form the basis of a just society.

What Are Examples of Natural Law In Systems of Government?

In the U.S. Constitution, the right of citizens to life, liberty, and the pursuit of happiness is a motto based on natural law. In the penal code, certain crimes are almost universally accepted as punishable, including murder and rape. These types of crimes are seen as damaging both the humanity of the victim and the social fabric of society.

How Does Natural Law Affect Business?

Natural law is seen in the concept of ethical business practices, especially the principle that a firm should not defraud its customers or other stakeholders. For instance, the marketing of drugs should be made with full disclosure of potential harms and not be sold as "snake oil."

What Are Some Flaws In Natural Law Theory?

Since natural law assumes universalizing rules, it does not account for the fact that different people or different cultures may view the world differently. For instance, if people interpret differently what it means for something to be fair or just, the results will differ.

The Bottom Line

Natural law is an ethical theory that claims that humans are born with a certain moral compass that guides behaviors. These inherited rules essentially distinguish the "rights" and "wrongs" in life. Under natural law, everyone is afforded the same rights, such as the right to live and the right to happiness. Natural law is evident in and shapes many of our laws, business policies, and human rights agendas. However, unlike these systems, its rules do not change and are inherently assigned to everyone.

Article Sources
Investopedia requires writers to use primary sources to support their work. These include white papers, government data, original reporting, and interviews with industry experts. We also reference original research from other reputable publishers where appropriate. You can learn more about the standards we follow in producing accurate, unbiased content in our editorial policy.
  1. Notre Dame Philosophical Reviews. "Aristotle and Natural Law."

  2. Constitutional Rights Foundation. "St. Thomas Aquinas, Natural Law, and the Common Good."

  3. Bombay Sarvodaya Mandal / Gandhi Book Centre. "Seven Deadly Sins As Per Mahatma Gandhi."

  4. The Martin Luther King, Jr. Research and Education Institute, Stanford University. "Letter from Birmingham Jail: Analysis 2," Page 4.

  5. Stanford Encyclopedia of Philosophy. "School of Salamanca."

  6. Pomona College. "Locke on Rights and Property."

  7. Foundation for Economic Education. "Natural Liberty."

  8. Britannica. "Invisible Hand."

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