What Is Law? Natural Law, Positivism, and the Question of Obligation

Jurisprudence begins with a deceptively simple question: what distinguishes law from a mere command backed by threat, or from a moral rule, or from a social custom? Ancient and medieval thinkers largely answered through natural law theory, holding that human-made law derives its validity and authority from a higher moral order — for the Stoics and Cicero, from reason inherent in the cosmos; for Aquinas, from divine reason as revealed through natural human faculties. On this view, an unjust law, in the famous formula attributed to Augustine and elaborated by Aquinas, is 'not really law at all' (lex iniusta non est lex), meaning legal validity and moral validity are conceptually bound together.

Modern legal positivism, developed by Jeremy Bentham and John Austin in nineteenth-century Britain and refined by H.L.A. Hart in the twentieth century, rejects this fusion. Austin defined law as the command of a sovereign backed by sanction, habitually obeyed; Hart refined this into a more sophisticated 'rule of recognition' theory in The Concept of Law (1961), arguing that a legal system is a union of primary rules (which govern conduct) and secondary rules (which specify how primary rules are made, changed, and adjudicated), and that a rule counts as law if it satisfies the community's ultimate rule of recognition — regardless of whether it is just. For positivists, the existence of law and its moral merit are separate questions: an unjust law is still law, though it may be a bad law that ought to be resisted or repealed.

Hans Kelsen's 'pure theory of law' pushed positivism further, seeking to strip jurisprudence of all sociological, psychological, and moral content and analyse law as a self-contained hierarchical system of norms, each deriving validity from a superior norm, ultimately resting on a hypothetical 'basic norm' (Grundnorm) that is presupposed rather than derived. Kelsen's framework proved influential in constitutional theory worldwide, including in Indian constitutional jurisprudence, where courts have occasionally invoked Grundnorm-like reasoning when assessing the validity of extra-constitutional actions such as the 1975 Emergency.

Ronald Dworkin, writing against Hart in Taking Rights Seriously (1977) and Law's Empire (1986), argued that legal positivism cannot adequately explain 'hard cases' where no clear rule dictates an outcome, because judges in such cases do not merely exercise discretion but appeal to underlying principles of political morality that are part of the law properly understood; law, for Dworkin, is an 'interpretive concept' aiming at the best moral justification of a community's legal practice. This debate between Hart and Dworkin — over whether law and morality are conceptually separable — remains the central axis of Anglo-American jurisprudence and has direct echoes in Indian debates over whether judges interpreting the Constitution's vague terms like 'equality' or 'personal liberty' are discovering law or making it.

American legal realism, associated with Oliver Wendell Holmes Jr. and later the Critical Legal Studies movement, offered a still more sceptical view: law is best understood not as a set of rules but as a prediction of what courts will actually do, shaped by judges' backgrounds, biases, and social context as much as by legal texts. Holmes's famous 'bad man' theory of law — that a client cares only about what a court will actually decide, not abstract legal principle — reoriented legal scholarship toward sociological and empirical study of how law functions in practice rather than how it is formally stated.

These competing theories are not merely academic; they shape how judges, lawyers, and citizens argue about controversial cases. When the Indian Supreme Court in cases like Kesavananda Bharati (1973) held that Parliament cannot amend the Constitution's 'basic structure', it was implicitly drawing on ideas resembling natural law and Dworkinian interpretivism — that some principles are so fundamental they constrain even properly enacted law. Understanding these frameworks equips students to see that behind every legal argument lies a deeper, often unstated, theory of what law is and why it binds us.