IUS and LEX. Constancy as Legal Principle in Roman Law

The Author investigates the function of ‘steadfastness’, corresponding to the Latin word constantia, in the Roman legal system, analysing its semantic and normative evolution from its republican origins to the late antique constitutions. Through an examination of literary and jurisprudential sources, this article highlights how constantia, as an ethical-political virtue of the mos maiorum, gradually transformed into a normative criterion in the interpretatio prudentium, influencing contractual and procedural law. In the Dominate, constancy took on technical-legal and political-ideological significance, becoming a fundamental principle of institutional stability and decision-making, of legal certainty, and consistency in imperial action.