The question ‘what is law?’ is a central and enduring question in jurisprudence, the philosophy of law. There is no single, universally agreed-upon answer. Instead, various schools of thought have developed competing theories to explain the nature, function, and authority of law. A simple definition might describe law as a system of rules created and enforced through social or governmental institutions to regulate behaviour. However, this definition is superficial and does not address the deeper questions about law's legitimacy and its relationship with morality. This essay will briefly examine three prominent theories that attempt to provide a more comprehensive answer: natural law, legal positivism, and legal realism.
Defining Law
A foundational definition of law was provided by the 19th-century legal positivist John Austin, who described law as a command issued by a sovereign, which is backed by the threat of a sanction (Wacks, 2020). The ‘sovereign’ is the person or body that is habitually obeyed by the bulk of society but does not habitually obey any other person or body. For Austin, a rule only qualifies as law if it fits this structure. For example, a parliamentary statute creating a criminal offence and setting a penalty for its breach fits this model perfectly. While this 'command theory' has been criticised for being overly simplistic and unable to account for all types of laws (such as those that grant powers rather than impose duties), it provides a clear starting point for understanding law as a formal system of state-backed authority.
Natural Law Theory
Natural law is one of the oldest theories of law, with origins in ancient Greek philosophy. Its central principle is that there is a necessary connection between law and morality. Proponents of natural law argue that there exists a ‘higher law’, based on morality, which positive (man-made) law must conform to. An influential maxim associated with this tradition is lex iniusta non est lex (an unjust law is not a true law). This suggests that a law which is fundamentally immoral or unjust lacks legal validity.
The theologian St Thomas Aquinas was a key figure who argued that law exists in different levels. Human law is only valid insofar as it is derived from, and does not contradict, natural law, which itself is derived from God’s eternal law (Bix, 2019). For a natural lawyer, a legal system's authority is therefore not just a matter of power and enforcement, but is grounded in its moral correctness. For example, post-war German courts used natural law reasoning to invalidate certain Nazi-era laws, arguing they were so contrary to fundamental principles of morality that they could not be considered valid law.
Legal Positivism
In direct contrast to natural law, legal positivism asserts that there is no necessary connection between law and morality. For positivists, the question of what the law is must be kept separate from the question of what the law ought to be. The validity of a law depends on its source or ‘pedigree’, not its moral content. So long as a law has been created by the correct legal authority and through the proper procedure, it is a valid law, regardless of whether it is just or unjust.
A leading modern positivist, H.L.A. Hart, developed a more sophisticated theory than Austin’s. In The Concept of Law, Hart argued that a legal system is a union of primary and secondary rules (Hart, 1961). Primary rules are those that impose duties or grant rights to individuals, such as the rules of criminal law or contract. Secondary rules are rules about the primary rules; they include rules of change (how laws are made), rules of adjudication (how courts decide disputes), and a master 'rule of recognition'. The rule of recognition is the ultimate criterion used by officials within a legal system to identify valid law. In the UK, the rule of recognition is, in simple terms, ‘what the Queen in Parliament enacts is law’. For Hart, it is the acceptance of this rule by officials that gives the legal system its foundation, not any moral principle.
Legal Realism
Legal realism, which emerged primarily in the United States in the early 20th century, offers a different perspective. Realists are less concerned with the abstract nature of law and more interested in how law works in practice. They argue that the ‘law in the books’ (statutes and case law) is often different from the ‘law in action’ (what actually happens in the legal system). For realists, the true law is what is decided by judges.
The jurist Oliver Wendell Holmes Jr. famously stated that law consists of “the prophecies of what the courts will do in fact, and nothing more pretentious” (Holmes, 1897, p. 461). This view suggests that legal rules are not the main determinant of a case's outcome. Instead, realists believe that judges are influenced by a wide range of other factors, including their personal experiences, political leanings, and even their mood. Law is therefore not a logical and predictable system of rules, but a more fluid and uncertain practice centred on judicial decision-making.
Conclusion
In conclusion, the question ‘what is law?’ does not have a single, straightforward answer. The theories of natural law, legal positivism, and legal realism provide three distinct and competing frameworks for understanding this complex concept. Natural law links law’s validity to morality, arguing that law must be just to be legitimate. Legal positivism separates law from morality, validating law based on its source and formal creation. Finally, legal realism shifts the focus from rules to practice, defining law as the actual decisions of judges. Each theory illuminates a different facet of law, and understanding them demonstrates that law can be conceived as a moral command, a social fact, or a practical reality.
References
Bix, B. H. (2019) Jurisprudence: Theory and Context. 8th edn. Sweet & Maxwell.
Hart, H. L. A. (1961) The Concept of Law. Oxford University Press.
Holmes, O. W. Jr. (1897) 'The Path of the Law', Harvard Law Review, 10(8), pp. 457–478.
Wacks, R. (2020) Understanding Jurisprudence: An Introduction to Legal Theory. 6th edn. Oxford University Press.
