The Concept of Law
In the Concept of Law, Hart set out to achieve two purposes: first to write an essay of descriptive sociology and second to provide an essay in analytical jurisprudence.
The starting point for the discussion is his disatisfaction with Austin's "Command Theory": this jurisprudential concept is meant to be ubiquitous in its application and holds that law is command backed by threat. Hart likens Austin's theory to the role of a gunman in a bank and tries to understand the differences between the gunman's orders and those made by law. For instance, the gunman forces us to obey but we do not feel inclined to obey him. This is one of the ways in which the law is not like a gunman.
Hart identifies three such imporant differences: content, origin and range. In terms of content, not all laws are imperative or coercive. Some are facilitative in allowing us to create contracts and other legal relations. Austin believed that every legal system had to have a sovereign who creates the law (origin) whilst remaining unaffected by it (range). In the bank scene, this is relected by the fact that the only source of commands is the gunman and he is not subject to anyone else's command. Hart argues that this is an inaccurate description of law. Lan have several sources and legislators are very often subject to the laws that they create.
Hart draws a distinction between a social habit (which people follow habitually but where breaking the habit does not bring about approbium - going to the cinema on Thursday for example) and a social rule (where breaking the rule is seen as wrong). We feel in some sense obligated by social rules and laws frequently appear to be types of social rule.
There are two perspectives to this: the external aspect which is the independently observable fact that people do tend to obey the rule with regularity, and the internal aspect which is the feeling by an individual of being in some sense obliged to follow the rule. It is from this internal sense that the law acquires its normative quality. The obedience by the populace of a rule is called efficacy. No law can be said to be efficacious unless followed by the majority of the populace.
But laws are more than rules of conduct. Laws can be divided up into two sorts: primary rules (rules of conduct) and secondary rules (rules addressed to officials and which set out to affect the operation of primary rules). Secondary rules deal with three problems: first the problem of uncertainty about what the law is (the secondary rule is called the rule of recognition and states whether the law is valid), second the problem of rigidity of rules (which requires rules of change allowing laws to be varied), and third the problem of how to resolve legal disputes (from which rules of adjudication arise). A legal system is "the union of primary and secondary rules."
Lastly, Hart lets us know that laws are much broader in scope than coercive orders. Frequently laws are enabling and so allow citizens to carry out authoritative acts such as the making of wills or contracts which have legal effect.
Hart's lasting value is therefore that he provides an explanation to a number of traditional jurisprudential issues such as "what is law?", "must laws be rules?", "what is the relation between law and morality?". He answers these questions by placing law into a social context while at the same time leaving the capability for rigorous analysis of legal terms. As a result Hart's theory is one of the most influential in jurisprudence.