Introduction
The question ‘what is law?’ is a foundational inquiry in legal philosophy, one which has no single, universally accepted answer. Defining law is not a simple task of linguistic definition but an exploration into its nature, sources, and function within society. While a layperson might define law as a set of rules enforced by the state, jurisprudential analysis reveals a far more complex picture. For centuries, legal theorists have presented competing accounts of what gives law its authority and what distinguishes it from other systems of rules, such as morality or social customs. This essay will explore this fundamental question by examining two of the most significant and opposing schools of thought in jurisprudence: legal positivism and natural law theory. By outlining the core tenets of these theories, with reference to key thinkers such as John Austin, H.L.A. Hart, and Lon Fuller, this essay will demonstrate that the definition of law depends heavily on the philosophical lens through which it is viewed.
Legal Positivism: Law as a Social Fact
Legal positivism is a school of thought that insists on the separation of law and morality. For positivists, the validity of a law is determined by its source and the process by which it was created, not by its moral content. This approach treats law as a social fact or convention, something that is ‘posited’ or laid down by human beings.
A classic formulation of legal positivism was presented by John Austin in the 19th century. Austin’s command theory defines law as “a command which obliges a person or persons… to a course of conduct” (Austin, 1832). In his view, a law is a command issued by a sovereign, who is a person or body habitually obeyed by the bulk of society and who does not habitually obey any other superior. Crucially, this command must be backed by the threat of a sanction or punishment for non-compliance. For Austin, whether a rule is a law depends on a simple empirical test: was it commanded by the sovereign? This provides a clear, if somewhat rigid, framework for identifying law. However, Austin’s theory has faced significant criticism. H.L.A. Hart, for instance, argued that it fails to account for many types of laws found in modern legal systems. Laws that grant powers, such as those governing contracts or marriage, do not fit the model of a command backed by a threat. Furthermore, the concept of a sovereign who is above the law is problematic in constitutional democracies where the government itself is bound by legal rules (Hart, 2012).
Responding to these criticisms, H.L.A. Hart developed a more sophisticated version of positivism. In The Concept of Law, Hart (2012) described law not as a series of commands, but as a system of rules. He distinguished between two types of rules: primary rules and secondary rules. Primary rules are duty-imposing rules that govern conduct, such as the criminal law prohibitions against theft or assault. Secondary rules are power-conferring rules that allow for the creation, modification, and adjudication of the primary rules. Hart identified three key secondary rules: the rule of change (governing how laws are made), the rule of adjudication (governing how legal disputes are settled), and, most importantly, the 'rule of recognition'. The rule of recognition is a social rule accepted by officials that specifies the criteria for legal validity within a particular system. In the UK, for example, the rule of recognition might be summarised as ‘what the Queen in Parliament enacts is law’. For Hart, it is this ultimate rule, rather than a sovereign's command, that provides the foundation of a legal system. This model accommodates a wider range of laws and better reflects the structure of modern legal systems. While Hart maintains the positivist separation of law and morals, acknowledging that a law can be legally valid yet morally reprehensible, he also accepted that the interpretation of legal rules often involves moral considerations in borderline cases.
Natural Law: Law and Morality Intertwined
In direct opposition to legal positivism, natural law theory asserts that there is a necessary connection between law and morality. From this perspective, the authority of law is derived not just from its human source, but from its conformity to a higher moral order. This tradition posits that there are universal moral principles, discoverable through human reason, which positive (man-made) law must reflect in order to be considered true law. The classic maxim of this school of thought is lex iniusta non est lex: an unjust law is not a law at all.
While its origins can be traced back to ancient thinkers like Aristotle and Cicero, natural law theory was given a modern articulation by Lon Fuller in his response to Hart. Fuller (1969) proposed a 'procedural' version of natural law, focusing not on the substantive moral content of laws, but on the formal and procedural requirements a system of rules must satisfy to be called a legal system. He argued that law has an ‘inner morality’ which consists of eight principles of legality. These are:
- Laws must exist (not ad hoc decisions).
- Laws must be promulgated (made public).
- Laws should not be retroactive.
- Laws must be clear and understandable.
- Laws must not be contradictory.
- Laws must not require the impossible.
- Laws must remain relatively constant over time.
- There must be congruence between the laws as announced and their administration.
For Fuller, a system that systematically fails to meet these principles—for example, one based on secret, retrospective, and contradictory decrees—is not simply a bad legal system; it is not a legal system at all. These principles constitute a moral framework for law-making, ensuring that the law is capable of guiding human conduct fairly and effectively.
The debate between Hart and Fuller was famously conducted against the backdrop of the Nazi regime in Germany. The question of whether the grossly immoral laws of the Third Reich were legally valid posed a direct challenge to legal positivism. Hart, upholding the separation thesis, would argue that as repugnant as they were, Nazi laws were valid according to the rule of recognition that existed in Germany at the time. To declare them 'not law' would be to confuse a legal question with a moral one. The correct approach, for Hart, would be to acknowledge their legal validity but refuse to obey or apply them on moral grounds, or to retroactively invalidate them with new legislation (Hart, 1958). By contrast, Fuller, along with other natural law thinkers like Gustav Radbruch, argued that the Nazi system had departed so far from basic principles of morality and legality that its edicts had forfeited their claim to be called law (Fuller, 1958). For them, the injustice was so extreme that it invalidated the legal status of the rules. This demonstrates the fundamental divide: for the positivist, law is about formal validity; for the natural lawyer, it is ultimately about justice.
Conclusion
The question 'what is law?' does not yield a simple conclusion. As this essay has shown, the answer depends fundamentally on whether one believes law can be separated from morality. Legal positivism, from Austin's command theory to Hart's more nuanced system of rules, provides a framework for identifying law based on its social sources and formal pedigree, without recourse to moral judgment. This approach offers clarity and certainty, explaining law ‘as it is’, rather than ‘as it ought to be’. In contrast, natural law theory, as articulated by thinkers like Fuller, insists that for a set of rules to truly be considered ‘law’, it must meet certain moral and procedural standards. This perspective provides a basis for challenging the legitimacy of unjust state actions, arguing that a system that violates the fundamental principles of justice is not worthy of the name ‘law’. Ultimately, neither theory completely captures the complex reality of law. Modern legal systems often operate on a largely positivist basis, yet judicial reasoning and constitutional principles are frequently infused with moral considerations. The ongoing debate between these two perspectives shows that any attempt to define law must grapple with its dual nature as both a system of power and an aspiration for justice.
References
Austin, J. (1832) The Province of Jurisprudence Determined. John Murray.
Fuller, L.L. (1958) 'Positivism and Fidelity to Law: A Reply to Professor Hart'. Harvard Law Review, 71(4), pp. 630-672.
Fuller, L.L. (1969) The Morality of Law. Revised edition. Yale University Press.
Hart, H.L.A. (1958) 'Positivism and the Separation of Law and Morals'. Harvard Law Review, 71(4), pp. 593-629.
Hart, H.L.A. (2012) The Concept of Law. 3rd edition. Oxford University Press.
