Legal positivism is a school of thought of philosophy of law and jurisprudence

Jurisprudence

Jurisprudence is the theory and philosophy of law. Scholars of jurisprudence, or legal theorists , hope to obtain a deeper understanding of the nature of law, of legal reasoning, legal systems and of legal institutions...

, largely developed by nineteenth-century legal thinkers such as Jeremy Bentham

Jeremy Bentham

Jeremy Bentham was an English jurist, philosopher, and legal and social reformer. He became a leading theorist in Anglo-American philosophy of law, and a political radical whose ideas influenced the development of welfarism...

 and John Austin

John Austin (legal philosopher)

John Austin was a noted British jurist and published extensively concerning the philosophy of law and jurisprudence....

. However, the most prominent figure in the history of legal positivism is H.L.A. Hart, whose work The Concept of Law caused a fundamental re-thinking of the positivist doctrine and its relationship with the other principal theories of law. In more recent years the central claims of legal positivism have come under significant attack from Ronald Dworkin.

It is difficult to summarize positivist thinking, but it is generally accepted that the central claim of legal positivism is the following:

"In any legal system, whether a given norm is legally valid, and hence whether it forms part of the law of that system, depends on its sources, not its merits."
Legal positivists make some distinctive claims about what constitutes legal validity.