Natural Law

The notion of a natural law that governs all human beings throughout the globe and provides a standard for ethical behavior in all parts of the world has been a persistent feature of ethical thought from ancient times to the present. This entry considers the initial unfolding of the cosmopolitan character of natural law, the historical stages in which it became more explicit, the challenges it received from competing theories, renewed interest in the 20th century, and current empirical confirmations.

Roman Stoics, at the time when the Pax Romana was spreading throughout the world and when philosophers emphasized the harmonious structure and laws of the cosmos, began to enunciate a universal “law of nature.” Thus, Cicero (106–43 BCE) in On the Republic speaks of a law that cannot be contradicted by any other law and is not liable either to derogation or abrogation. Neither the senate nor the people can give any dispensation for not obeying this universal law of justice. According to Cicero, it needs no other expositor and interpreter than our own conscience. It is not one thing at Rome and another at Athens, one thing today and another tomorrow, but in all times and nations, this universal law must forever reign, eternal and imperishable. It is the sovereign master and emperor of all beings. God himself is its author, its promulgator, its enforcer. Later, the freed slave and Stoic philosopher Epictetus (60–138 CE) brought out the further implications of this concept—an ideal of world citizenship and human equality under a higher law that superseded all local or national laws.

In the Middle Ages and the Renaissance, attempts were made to define key precepts of the lex naturalis (law of nature). Thomas Aquinas (1225–1274), summarizing the efforts of prior philosophers and Roman jurists, focused on three pivotal inclinations of human nature, which superseded other inclinations and had the force of law: (1) the law of self-preservation, which humans have in common with all beings in the world; (2) the law of procreation and care for offspring, which humans have in common with animals; and (3) the law specific to rational beings to search for the truth and to organize social structures in reasonable and harmonious ways. These precepts were expanded and reformulated by later scholastics in the Catholic tradition. The Spanish Dominicans Francisco de Vitoria (1492–1546) and Bartolomé de las Casas (1474–1566), responding to problems connected with colonizations and conquests in the Americas, developed principles of the natural rights of indigenous peoples as corollaries to natural law theory.

In the wake of the Reformation, Protestant thinkers, such as Richard Cumberland (16311718) and Samuel Pufendorf (1632–1694), partially in response to the perceived dangers of the theory of Thomas Hobbes (1588–1679) concerning a natural “war of all against all,” developed theories of natural law emphasizing the innate altruism and sociability of human beings. Of particular interest from a global perspective was the three-volume Law of War and Peace of the Dutch jurist Hugo Grotius (1583–1645), which looked to natural law as the only trustworthy basis for international law and treaties between nations.

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