The Forgotten Meaning of Certainty of Law: How Ancient Legal Systems Achieved Long-Term Stability

Stable and predictable legal frameworks are crucial for economic development, as they allow individuals and businesses to plan for the long-term. However, modern legislatures often undermine legal certainty through excessive regulation and frequent changes. By exploring how the ancients conceived of legal certainty, we can relearn the value of stable legal norms that withstand legislative tinkering.

The Greek Conception of Legal Certainty: Written Precision

The ancient Greeks pioneered the idea that clearly written laws provided legal certainty by constraining the arbitrary whims of rulers. As Italian law professor Bruno Leoni explained, Greeks believed certainty came from “precisely worded” statutes, differentiating law from a “tyrant’s” random orders. This notion of legal certainty as written precision remains influential today, as codified constitutions and legislation allow citizens to know their rights and duties.

However, the Athenian democracy’s unrestrained lawmaking undermined lasting certainty. With citizens constantly proposing new statutes, the law transforming daily made long-term planning impossible. The Athenians recognized this problem. In the 5th century BCE, reforms required proposed bills to undergo review for consistency with existing laws, holding proponents accountable for new legislation’s defects. Yet written precision still provided only fleeting certainty.

The Roman Concept of Legal Certainty: Long-Term Stability

Unlike the Greeks, the Romans achieved legal certainty not through precise written codes but by maintaining the stability of unwritten norms and principles over centuries. Roman private law (jus civile) evolved gradually through jurists’ reasoned analysis of cases, keeping it insulated from legislators. While statutes existed, Leoni emphasizes how Roman citizens rarely invoked written rules in disputes, instead appealing to the “common heritage” of interpretations accumulated over generations.

This organic development of law through precedent meant citizens could plan ahead without worrying about sudden legislative changes. As Leoni writes, “Nobody enacted that law; nobody could change it by any exercise of his personal will.” The Roman jurist discovered law like a scientist discovers natural phenomena – not by fiat but by “dispassionate investigation.” This conceptualization of predictable yet uncodified law was strikingly similar to the English “rule of law” tradition.

The English “Rule of Law” Tradition

The English common law system also provided certainty through organic legal evolution, not top-down codification. English judges aimed to uphold the continuity of rulings from “former ages,” keeping the law “consonant to itself” over time. This required studying jurisprudence to discern the legal principles that had endured for centuries. English jurists like Sir Matthew Hale thus counseled against injecting “new theories” that might disrupt settled law.

However, over recent centuries, English law has increasingly conflated law with legislation, undermining this heritage of legal certainty. Parliament now overturns common law precedents through statutes. As Leoni laments, the English “rule of law” risks degenerating into an état de droit where law’s certainty derives only from Parliamentary enactment, not judges’ role upholding past decisions. This challenges long-range economic planning.

Ancient Legal Certainty Encouraged Sound Economic Planning

The Romans’ and early English’s vision of predictable yet flexible legal norms allowed citizens to make investments and contracts with confidence their rights would remain stable for generations. By avoiding constant legislative turbulence, organic legal development enabled dependable economic decision-making.

In contrast, today’s combination of proliferating regulation and legislation providing only fleeting certainty breeds economic uncertainty. Businesses cannot plan for the long-term when statutes rewrite the rules overnight. Excessive lawmaking sows confusion instead of establishing a sturdy social framework undergirding investment and commerce.

We Must Relearn the Ancient Lesson of Legal Certainty

Modern societies struggle with the contradiction of wanting both written precision in law and legal stability enabling sound planning. We try legislating certainty into existence, forgetting the ancients’ wisdom that restrained evolution of unwritten custom provides greater lasting predictability. As we have lost this appreciation of certainty as continuity, not codification, revisiting how Greco-Roman jurisprudence and the early English common law achieved long-term stability can help us rediscover the social conditions necessary for freedom and prosperity.


The ancients understood certainty of law not as detailed written rules but as the steadiness of evolving norms and interpretations over generations. By recovering this conception of legal certainty as long-term stability and predictability rather than a fixed written code, we can recreate the secure social environment that allows responsible economic and civic planning.