The unwritten body of universal moral principles that underlie the ethical and legal norms by which human conduct is sometimes evaluated and governed. Natural law is often contrasted with positive law, which consists of the written rules and regulations enacted by government. The term natural law is derived from the Roman term jus naturale. Adherents to natural law philosophy are known as naturalists.
Naturalists believe that natural law principles are an inherent part of nature and exist regardless of whether government recognizes or enforces them. Naturalists further believe that governments must incorporate natural law principles into their legal systems before justice can be achieved. There are three schools of natural law theory: divine natural law, secular natural law, and historical natural law.
Divine Natural Law
Proponents of divine natural law contend that law must be made to conform to the commands they believe were laid down or inspired by God, or some other deity, who governs according to principles of compassion, truth, and justice. These naturalists assert that the legitimacy of any enacted human law must be measured by its consonance with divine principles of right and wrong. Such principles can be found in various Scriptures, church doctrine, papal decrees, and the decisions of ecclesiastical courts and councils. Human laws that are inconsistent with divine principles of morality, naturalists maintain, are invalid and should neither be enforced nor obeyed. St. Thomas Aquinas, a theologian and philosopher from the thirteenth century, was a leading exponent of divine natural law.
Secular Natural Law
The school of natural law known as secular natural law replaces the divine laws of God with the physical, biological, and behavioral laws of nature as understood by human reason. This school theorizes about the uniform and fixed rules of nature, particularly human nature, to identify moral and ethical norms. Influenced by the rational empiricism of the seventeenth-and eighteenth-century Enlightenment thinkers who stressed the importance of observation and experiment in arriving at reliable and demonstrable truths, secular natural law elevates the capacity of the human intellect over the spiritual authority of religion.
Historical Natural Law
Another school of natural law is known as historical natural law. According to this school, law must be made to conform with the well-established, but unwritten, customs, traditions, and experiences that have evolved over the course of history. Historical natural law has played an integral role in the development of the Anglo-American system of justice. When King James I attempted to assert the absolute power of the British monarchy during the seventeenth century, for example, English jurist Sir Edward Coke argued that the sovereignty of the crown was limited by the ancient liberties of the English people, immemorial custom, and the rights prescribed by Magna Charta in 1215. Magna Charta also laid the cornerstone for many U.S. constitutional liberties. The Supreme Court has traced the origins of grand juries, petit juries, and the writ of Habeas Corpus to Magna Charta.