Origins of natural law
Natural law theory holds that universal principles of justice and morality exist independently of any laws humans create. These principles can be discovered through reason alone, and they're supposed to serve as a standard against which all human-made laws can be measured. The theory has deep roots in ancient Greek and Roman thought and has shaped Western legal traditions for centuries.
Natural law stands in contrast to legal positivism, which says a law is valid simply because it was enacted through proper procedures by a recognized authority. Natural law theorists reject that view: they argue a law that violates fundamental moral principles isn't truly a valid law at all.
Defining natural law
Natural law refers to a set of universal, objective, and immutable principles that are inherent in the nature of things and discoverable through reason and reflection. These principles are considered the foundation of morality and justice, serving as a higher law that should guide human behavior and inform the creation of positive laws (human-made laws).
Natural law vs. positive law
This distinction is central to understanding natural law theory:
- Natural law consists of universal moral principles that exist independently of any government or legal system. A law is only truly valid if it conforms to these principles.
- Positive law refers to the specific laws enacted by human authorities (legislatures, courts, regulatory agencies). Under legal positivism, these laws are valid as long as they were enacted through proper procedures, regardless of their moral content.
Conflicts arise when positive laws appear to violate natural law principles. For instance, laws that once permitted slavery were valid positive law in their time, but natural law theorists would argue they were never legitimate because they violated the fundamental moral principle of human dignity. These conflicts raise difficult questions about whether citizens are obligated to obey unjust laws or whether resistance is justified.
Key principles of natural law
Natural law theory rests on a few core claims about morality and its relationship to law.
Morality as foundation
Natural law theorists argue that morality is the foundation of law. Human-made laws must conform to universal moral principles to be considered valid and legitimate. Laws that violate fundamental moral principles, such as laws permitting slavery or genocide, are not truly laws at all and can be legitimately resisted or disobeyed.
This is a strong claim, and it directly opposes the positivist position. A legal positivist would say an unjust law is still a law; a natural law theorist would say it isn't.
Universal and immutable
Two defining features of natural law principles:
- Universal: They apply to all people in all times and places, regardless of cultural, social, or political differences.
- Immutable: They cannot be changed or overridden by human authorities or shifting social norms.
These features give natural law its power as a tool for critique. If moral principles are universal and unchanging, then any legal system, in any era, can be evaluated against them and found wanting.
Key principles commonly associated with natural law include the right to life, liberty, and property; the duty to respect the rights of others; and the obligation to act in accordance with reason and the common good.
Historical development of natural law
The concept has evolved significantly across different eras, though the core idea of a higher moral law guiding human behavior has remained constant.
Ancient Greek philosophers
- Aristotle distinguished between natural justice (universal and unchanging) and conventional justice (which varies across societies). This distinction laid the groundwork for later natural law thinking.
- Stoic philosophers developed the idea of a universal law of nature governing all things, including human behavior. They argued individuals should live in accordance with this rational natural order.
These Greek ideas provided the philosophical foundation that Roman law and medieval Christian thinkers would later build upon.
Medieval Christian thinkers
Thomas Aquinas is the most important figure in this period. He synthesized Aristotelian philosophy with Christian theology to create a comprehensive natural law framework.
Aquinas argued that:
- God established an eternal law governing all of creation.
- Natural law is humanity's participation in that eternal law, accessible through reason.
- Human reason can discover the basic principles of natural law by reflecting on human nature and the created order.
- Human law (positive law) should be derived from and consistent with natural law.
This framework profoundly influenced Western legal and political thought and remains the starting point for many natural law arguments today.
Contemporary perspectives on natural law
Natural law theory remains active in legal and political philosophy, though it has adapted in response to challenges from legal positivism, moral relativism, and other competing theories.
Modern legal theorists
- John Finnis developed what's often called "new natural law theory." Rather than grounding natural law in a metaphysical account of human nature, Finnis identifies a set of basic human goods (life, knowledge, play, aesthetic experience, sociability, practical reasonableness, and religion) that are self-evidently valuable. Practical reasonableness then guides how we pursue these goods.
- Robert P. George has built on Finnis's work, applying natural law reasoning to contemporary legal and political debates.
These modern theorists have made natural law arguments more accessible to secular audiences by shifting the emphasis from theology to reason and human flourishing.
Criticisms and limitations
Natural law theory faces several significant challenges:
- Legal positivists argue that law's validity depends on its source and enactment, not its moral content. Mixing law and morality, they claim, creates confusion about what the law actually is.
- Moral relativists question whether universal and immutable moral principles exist at all, arguing that moral norms are culturally and historically contingent.
- Historical misuse: Natural law arguments have been used to justify oppressive arrangements, including the divine right of kings and the subordination of women, raising questions about whether the theory provides reliable moral guidance.
- Indeterminacy: Critics argue natural law often fails to give clear answers in hard cases where moral principles conflict with one another.
Influence on legal systems
Despite these criticisms, natural law has left a deep imprint on legal systems worldwide, particularly in the Western tradition.
Role in constitutional law
Natural law principles have significantly shaped constitutional law, especially in the United States and other common law systems.
- The idea that certain fundamental rights pre-exist government and must be protected by constitutional guarantees (free speech, religious liberty, due process) has its roots in natural law thinking.
- Judicial review, the power of courts to strike down legislation that violates constitutional rights, draws on the natural law idea that courts have a duty to uphold fundamental principles against government overreach.
Impact on human rights
Natural law's influence on international human rights law is especially visible in the post-World War II era. The horrors of the Holocaust demonstrated the dangers of a purely positivist approach: Nazi laws were validly enacted, yet clearly unjust.
- The Universal Declaration of Human Rights (1948) reflects natural law principles in affirming the "inherent dignity" and "equal and inalienable rights of all members of the human family."
- Later treaties like the International Covenant on Civil and Political Rights and the European Convention on Human Rights also draw on natural law ideas about universal, inalienable rights.
Natural law in practice
Natural law isn't just abstract philosophy. It shows up in real legal reasoning and policy debates.
Judicial decision-making
Judges, particularly in common law systems, sometimes draw on natural law principles when interpreting and applying the law. A well-known example:
In Riggs v. Palmer (1889), a New York court held that a murderer could not inherit from his victim's estate. No statute explicitly prohibited the inheritance, but the court invoked the natural law principle that no one should profit from their own wrongdoing.
This case illustrates how natural law reasoning can fill gaps in positive law and provide moral grounding for judicial decisions.
Shaping public policy
Natural law arguments frequently appear in movements for legal and social change:
- The civil rights movement of the 1950s and 1960s drew heavily on natural law reasoning. Martin Luther King Jr.'s Letter from Birmingham Jail explicitly invoked natural law to argue that segregation laws were unjust and therefore not binding on the conscience.
- Contemporary debates about same-sex marriage, abortion, and assisted suicide often involve competing natural law claims about fundamental moral rights and the proper role of law in protecting or limiting those rights.
These examples show that natural law theory, whatever its philosophical limitations, continues to function as a practical tool for arguing about what the law should be.