In the Anglophone world, the pivotal writer was H.L.A. Hart, who argued that the law should be understood as a system of social rules. Hart rejected Kelsen's views that sanctions were essential to law and that a normative social phenomenon, like law, can not be grounded in non-normative social facts. Hart really revived analytical jurisprudence as an important theoretical debate in the twentieth century through his book The Concept of Law. As the chair of jurisprudence at
Rules, said Hart, are divided into primary rules (rules of conduct) and secondary rules (rules addressed to officials to administer primary rules). Secondary rules are divided into rules of adjudication (to resolve legal disputes), rules of change (allowing laws to be varied) and the rule of recognition (allowing laws to be identified as valid). The "rule of recognition", a customary practice of the officials (especially judges) that identifies certain acts and decisions as sources of law. A pivotal book on Hart was written by Neil MacCormick in 1981 (second edition due in 2007), which further refined and offered some important criticisms that led MacCormick to develop his own theory (the best example of which is his recently published Institutions of Law, 2007). Other important critiques have included that of Ronald Dworkin, John Finnis, and Joseph Raz.
In recent years, debates about the nature of law have become increasingly fine-grained. One important debate is within legal positivism. One school is sometimes called exclusive legal positivism, and it is associated with the view that the legal validity of a norm can never depend on its moral correctness. A second school is labeled inclusive legal positivism, and it is associated with the view that moral considerations may determine the legal validity of a norm, but that it is not necessary that this is the case.
