Natural Law is the concept that there is inherent in nature a set of laws, perhaps created by God, to which humans must adhere. These laws are considered to be self-evident, in that they are able to be observed by everyone. It is debated whether or not natural law actually exists; in particular, it conflicts with sola scriptura.
These are distinguished from physical law in that they can be broken or disobeyed, and from civil law and common law by the fact that they have no enforcement agencies. However, it can be argued that it forms the foundation for many legal systems in the world.
Natural Law Theory is the official ethic of the Roman Catholic Church. It was espoused by Thomas Aquinas, and argues that, as God created the universe and revealed His mind to man through the order inherent in things discernible by the natural light of reason, man can use his reason to discern God's Will by studying the natural world. For instance, a study of the male and female reproductive system naturally leads any sane person to see that their natural function is to come together for the purpose of procreation- so any acts excluding this purpose, such as homosexuality, onanism, contraception, and acts during menstruation, are wrong. Before the encyclical Casti Connubii in 1930, some Catholics believed that acts during pregnancy or after menopause were also wrong as against natural law.
- Richard Hooker's Discourse on Natural Law in the Context of the Magisterial Reformation
- Pope John Paul II, Veritatis Splendor; International Theological Commission, The Search for Universal Ethics: A New Look at the Natural Law.
- See, for example, Summa Theologiae, I-II, qq. 90-94.