Medieval theories of natural law

In medieval texts the term ius naturale can mean either natural law or natural right; for the latter sense see the article Natural Rights ”. Ius naturale in the former sense, and also lex naturalis, mean the universal and immutable law to which the laws of human legislators, the customs of particular communities and the actions of individuals ought to conform. It is equivalent to morality thought of as a system of law. It is called “natural” either (a) because it is taught by natural instinct, i.e. some capacity innate in human beings, or (b) because it is accessible to “natural reason”, i.e. to personal reflection independent of any special revelation from God (such as the Christian faith claims to be) and independent of the moral authority of other human beings; or for both reasons.