Natural law is the claim that certain legal or moral principles exist independent of human enactment — that some things are right or wrong regardless of what any legislature, court, or sovereign declares. The tradition holds that these principles are discoverable through reason, accessible to all rational beings, and binding on all human societies.
The genealogy is long. Aristotle distinguished natural justice (universal and unchanging) from conventional justice (variable by community). Stoic philosophy developed the idea of a universal rational order that grounds moral obligation. Aquinas synthesized natural law with Christian theology: God’s eternal law is partially accessible to human reason as natural law, which in turn provides the standard against which human law must be measured. An unjust law — one that violates natural law — is “no law at all” (lex iniusta non est lex).
The early modern period secularized natural law. Hugo Grotius argued that natural law would hold “even if we should concede that there is no God.” Locke grounded natural rights — life, liberty, property — in a pre-political state of nature. The American Declaration of Independence appeals to “the Laws of Nature and of Nature’s God” and asserts that certain rights are “unalienable” — beyond the reach of government. These are natural law claims: political authority is limited by principles it didn’t create and can’t override.
Legal positivists from Bentham onward have rejected natural law as metaphysical speculation dressed in legal vocabulary. If you can’t empirically identify natural law or reach consensus on its content, it’s not doing legal work — it’s doing political work under a legal label. The positivist challenge is powerful but doesn’t eliminate the natural law impulse. International human rights law, the Nuremberg trials’ appeal to principles above positive law, and constitutional doctrines like substantive due process all draw on natural law reasoning even when they don’t use the term.
Related terms
- Rights — the concept natural law grounds in pre-political authority
- Legitimacy — the quality natural law claims to provide independent of positive enactment
- Customary law — another non-positivist source of legal obligation
- Rule of law — the principle natural law theorists claim positive law must embody
- Constitutionalism — the institutional form through which natural law limits are often enforced