What Is Natural Law?

Natural law is a theory in ethics and philosophy that says that human beings possess intrinsic values that govern our 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 are ancient, stemming from the times of Plato and Aristotle.
  • Natural law is constant throughout time and across the globe because it is based on human nature, not on culture or customs.

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, but rather 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. 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 "man-made 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)—considered by many to be the father of natural law—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; that this natural justice is positive, and does not exist by "people thinking this or that."
  • 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. 
  • The author C.S. Lewis (1898–1963) explained it this way: “According to the religious view, what is behind the universe is more like a mind than anything else we know… it is conscious, and has purposes and prefers one thing to another. There is a 'something' which is directing the universe, and which appears to me as a law urging me to do right.” (Mere Christianity, pg. 16–33)

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. 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 sort of ethical assumptions. 

Examples of Natural Law In Economics 

  • Early economists of the medieval period, including the aforementioned Aquinas as well as 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 father 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.