Natural law is a moral law that philosophers and theologians have taught is inherent in human nature, commanding what is right and forbidding what is wrong. They have held that while individual ideas of right and wrong may vary in detail from one time and place to another, there are certain basic demands of natural justice that are common to all persons. Examples are treating one's neighbors fairly and honoring one's parents. The commands of natural law arise out of the nature of man and can be discovered by reason or are presented by man's conscience.
The idea of natural law is thought to have first developed among the ancient Greeks. A notable early example of the idea is found in Sophocles' tragic play Antigone, in which the view is advanced that men have the natural right to disobey unjust human laws if they conflict with the higher natural law. The Greek philosopher Aristotle agreed with this view. The later Roman Stoic philosophers went further, arguing that since all men have the same human nature and are subject to the same moral law, all men are essentially equal as human beings.
Under Stoic influence the Roman statesman Cicero became an eloquent
spokesman for the natural law idea. Later Roman jurists incorporated
the natural law concept into Roman law, such as the jus gentium, the
earliest form of international law.
The Christian tradition of natural law can be traced to St. Paul. In his Epistle to the Romans (2:14-15), Paul said that just and goojl Gentiles, who have no divinely revealed law, such as the Ten Commandments, "do by nature the things of the law...; they show the work of the law written in their hearts, their conscience bearing witness therewith." In the 13th century, St. Thomas Aquinas produced a systematic treatment of the topic, teaching that God created human nature in the image of His own Divine nature and that the natural law in man is the image of the eternal law, or the Divine reason itself.
After the Middle Ages the concept of natural law was employed by the Dutch jurist and humanist Hugo Grotius in developing modern international law. It was also important in the development of Anglo-American law and Western political theory. For example, the English jurist Sir William Blackstone insisted that the authority of human law is based on natural law and that any law conflicting with natural law is invalid. The political philosophers Thomas Hobbes and John Locke in England and Jean Jacques Rousseau in France declared natural law to be the basis of natural rights to life, liberty, and property. They further held that government-is set up to promote men's rights. The natural law and related natural rights philosophy inspired men rebelling against oppressive government. The concepts came to be embodied in the U.S. Declaration of Independence in 1776 and in the French Declaration of the Rights of Man and of the Citizen in 1789.
The natural law concept fell into disuse during the 19th century, when scholars devoted themselves to studying and describing the laws observably in force in different societies. However, there was a great renewal of interest in natural law in the 20th century in reaction to totalitarian governments that denied human rights and insisted that justice consist of absolute obedience to the laws of the state. Following World War II, Nazis charged with war crimes argued that they had disobeyed no law but had simply obeyed the commands of their government. Many were convicted on the argument that there is a higher natural law of justice, under whose standards the accused persons should have disobeyed the Nazi regime. To aid human rights against further violation, the United Nations in 1948 adopted the Universal Declaration of Human Rights.