Definition
Latin: "that which is equitable and just." A foundational maxim of Roman law expressing the idea that law should conform to principles of equity and justice that transcend positive enactment. Aequum et bonum functioned not as a discrete legal rule but as an animating standard — a touchstone for judicial interpretation and the development of legal doctrine where strict application of written law would produce an unjust result.
In Roman legal thought, aequum et bonum served as the conceptual engine behind two broader bodies of law: the jus gentium (the law common to all peoples) and the jus naturale (natural law). Both drew their legitimacy, at least in part, from this underlying commitment to what was equitable and good — a recognition that valid law must track something deeper than the will of a particular sovereign or the text of a particular statute.
The phrase appears most famously in the Roman proverb summum jus, summa injuria — the highest law, the greatest injustice — which warns that rigid enforcement of legal rules without equity can itself become a form of injustice. Aequum et bonum was the corrective principle: the idea that courts and jurists should reach results that are fair as well as technically correct.
Why It Matters in Research
This term appears in historical legal sources primarily as a maxim rather than an operative legal standard, which shapes how researchers should approach it. In Bouvier and similar nineteenth-century dictionaries, it functions as a gateway concept — a brief entry that opens onto substantially larger doctrinal structures, particularly the Roman law categories of jus gentium and jus naturale.
Researchers working in equity jurisprudence, natural law theory, or the history of common law equity will encounter aequum et bonum as background principle rather than applied rule. It rarely appears in case reporters as a cited standard; it appears more often in treatises, law review commentary, and philosophical legal writing as a way of grounding equitable reasoning in something beyond judicial discretion.
The connection to jus gentium is particularly important for legal historians. Roman jurists used aequum et bonum to justify extending Roman legal protections to non-citizens and to rationalize rules that seemed to operate across different legal systems. This makes the term relevant to early international law scholarship and natural law jurisprudence from Grotius forward.
Researchers should be cautious about anachronistic reading. Modern equity doctrine — in the sense of English Chancery practice and its American descendants — is historically related to but not identical with Roman aequum et bonum. Treating the two as equivalent will produce interpretive errors when working with pre-modern sources.
Historical Dictionary Support
Bouvier's is spare but accurate: "that which is equitable and just" and "the basis, in Roman law, of much of the jus gentium, and jus naturale," citing Hunter's Roman Law (2nd ed.). This is the standard treatment. Historical legal dictionaries generally handle this term as a cross-reference point rather than a substantive entry, directing researchers to the fuller doctrines of jus gentium and natural law for meaningful content.
What historical dictionaries tend to understate is the procedural dimension of aequum et bonum in Roman practice. Roman praetors exercised considerable discretion in granting or denying remedies, and appeals to aequum et bonum functioned as a way of legitimating that discretion — analogous in some respects to what English Chancery would later call conscience. This functional similarity is worth noting when working across civil law and common law sources, though the institutional contexts differ significantly.
No meaningful divergence among historical dictionary sources on this term: it is consistently treated as a Latin maxim with a settled translation and a settled doctrinal location in Roman law foundations.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Equity; Natural Law; Jus Gentium