The natural law tradition is said to be one of the oldest jurisprudential school with a history of about 2500 years. From the time of the ancient Greeks up until the 17th century it was the only theory of law. Over years it came to be known through different names such as moral law, law of reason, law of god, higher law, universal law, unchanging law, immutable law & law of mankind and so on and so forth. The notions such as natural rights, human rights, due process & natural justice are all expressions of natural law. In fact the notion of natural rights was used as a basis in the American & French revolutionary movements to criticize the absolute powers of the sovereign. In particular the American Revolution led to the emergence of a natural right ‘no tax without representation’. Indeed the US Declaration of Independence defined life, liberty & pursuit of happiness as the inalienable rights. More recently the expression of natural law can be seen in the Universal Declaration of Human Rights which defines human rights as the rights a person has simply because he/she is a human. These are held by all persons equally, universally & forever.
Today the natural law tradition is divided between classical & contemporary natural lawyers. Plato, Aristotle, Stoics, Cicero, St Augustine & St. Thomas Aquinas are from the former category whereas John Finnis & Lon Fuller are from the latter category. Each of these philosophers has their own version of the natural law but there is one point on which all agree. This is the overlapping thesis: the contention that law & morality overlap or changing the expression there is a necessary connection between law & morality.