‘Legal Positivism’ theory was developed by

Legal positivism is a school of jurisprudence that asserts the existence and content of law depend on social facts rather than morality. While Thomas Hobbes is often cited as a pioneer who provided the foundation for positivist understanding through his 'command theory' of law, he is frequently categorized as a natural law theorist due to his secular version of natural law. The formal development and systematic formulation of legal positivism, specifically the 'command theory of positive law,' is attributed to John Austin in his seminal 1832 work, 'The Province of Jurisprudence Determined'. Austin, alongside Jeremy Bentham, established the 'separation thesis,' which distinguishes what the law is from what the law ought to be. T.H. Green is associated with political idealism, and Patrick Devlin is known for his debates with H.L.A. Hart regarding the enforcement of morality by law.

Sources

1. [1] https://en.wikipedia.org/wiki/Legal_positivism