Law must simultaneously satisfy two competing demands: it must be correct, meaning well-adapted to current social circumstances, and certain, meaning knowable and stable enough for citizens to form reliable expectations and long-term plans. This paper argues that these two properties are fundamentally in tension. Drawing on the work of Bruno Leoni and Friedrich Hayek, the paper examines how different conceptions of law—statutory legislation, common law, and emergent tradition—handle this tension. Leoni’s central insight, that legislation suffers from the same knowledge problem as central economic planning, is developed and extended. Just as no planner possesses sufficient local knowledge to set prices correctly, no legislature possesses sufficient information to enact laws that accurately reflect the norms and needs of a complex society. Three categories of costs attend any change in the law: switching costs, habit costs, and resistance costs. Each imposes burdens on citizens and erodes the moral authority that gives law its compliance-generating power, independent of formal enforcement. Leoni’s preferred alternative—judge-made common law rooted in tradition and the principle of Ex Eo Quod Plerumque Fit—offers greater certainty through its resistance to rapid change, while preserving a decentralized discovery process analogous to market price formation. Finally, an unresolved tension in Leoni’s framework is identified: without an external normative criterion, evolutionary legal processes offer no guarantee of just or efficient outcomes. The paper concludes that while no legal system can be perfect on all dimensions, a return to genuinely tradition-based common law adjudication would represent a meaningful improvement over modern legislative practice.

Continue reading Correct and Certain: Law Cannot Be Both