Abstract
The natural law theorist and the common law theorist both add an extra ingredient to their accounts of law.1 In contrast, the legal realist refuses to add a necessary ingredient. The legal realist refuses to acknowledge the authority of rules. Developing as a reaction to formalist jurisprudence, which took law to be deducible by reason from certain axioms or ethical principles, and traditionalist jurisprudence, which took law to be a product of historical development, legal realism attempts to understand law realistically, as it is actually decided. What unifies, and fatally poisons, formalist and traditionalist theories is that they attempt to offer explanations for why judges follow rules. All such explanations are bound to fail, according to legal realists, because there are indefinitely many ways to interpret a rule (or a statute or precedent), and positing a rule for interpreting rules only pushes back the indeterminacy into an infinite regress.