In jurisprudence and legal philosophy, legal positivism is the theory that the existence of the law and its content depend on social facts, such as acts of legislation, judicial decisions, and customs, rather than on morality. This contrasts with natural law theory, which holds that law is necessarily connected to morality in such a way that any law that contradicts morality lacks legal validity.
Thomas Hobbes defined law as the command of the sovereign. This idea was elaborated in the 18th and 19th centuries by legal philosophers such as Jeremy Bentham and John Austin, who argued that a law is valid not because it is intrinsically moral or just, but because it comes from the sovereign, is generally obeyed by the people, and is backed up by sanctions. Hans Kelsen developed legal positivism further by separating law not only from morality, as the early positivists did, but also from empirical facts, introducing the concept of a norm as an "ought" statement as distinct from a factual "is" statement. In Kelsen's view, the validity of a legal norm derives from a higher norm, creating a hierarchy that ultimately rests on a "basic norm": this basic norm, not the sovereign, is the ultimate source of legal authority.
In addition to Kelsen, other prominent legal positivists of the 20th century include H. L. A. Hart and Joseph Raz.