An approach to law that rejects natural law and contends that the law as laid down (positum) should be kept separate – for the purpose of study and analysis – from the law as it ought morally to be. In other words, a clear distinction must be drawn between “ought” (that which is morally desirable) and “is” (that which actually exists). The theory is associated especially with the thought of Jeremy Bentham (1748–1832), John Austin (1790–1859), H. L. A. Hart (1907–1992), and Hans Kelsen (1881–1973), who differ from one another in important respects but generally adhere to the above separability thesis. In addition, legal positivists normally adopt the so-called social fact thesis (that legal validity is a function of pedigree or related social facts) and the conventionality thesis (that social facts giving rise to legal validity are authoritative by virtue of social convention). See analytical jurisprudence; pure theory of law; utilitarianism. See also interpretive theory of law.