Some philosophers distinguish two types of rights, natural rights and legal rights.
- Natural rights are those that are not dependent on the laws or customs of any particular culture or government, and so are universal, fundamental and inalienable (they cannot be repealed by human laws, though one can forfeit their enjoyment through one's actions, such as by violating someone else's rights). Natural law is the law of natural rights.
- Legal rights are those bestowed onto a person by a given legal system (they can be modified, repealed, and restrained by human laws). The concept of positive law is related to the concept of legal rights.
Natural law first appeared in ancient Greek philosophy, and was referred to by Roman philosopher Cicero. It was subsequently alluded to by Saint Paul, and then developed in the Middle Ages by Catholic philosophers such as Albert the Great, his pupil Thomas Aquinas, and Jean Gerson in his 1402 work "De Vita Spirituali Animae." During the Age of Enlightenment, the concept of natural laws was used to challenge the divine right of kings, and became an alternative justification for the establishment of a social contract, positive law, and government – and thus legal rights – in the form of classical republicanism. Conversely, the concept of natural rights is used by others to challenge the legitimacy of all such establishments.