Definition
A contract of good faith. In Roman law, a class of contracts in which the judge was not confined to the strict letter of the agreement but was empowered to take into account all the equitable circumstances of the transaction — the intentions of the parties, the usages of trade, and the requirements of good faith (bona fides) — in determining the rights and obligations arising from the contract. The obligation owed under such a contract was measured not merely by what was expressly stipulated but by what good faith and fair dealing required.
Contractus bonae fidei stood in contrast to contractus stricti juris (contracts of strict law), in which the judge was bound to the precise terms of the agreement and could not look beyond the literal words to supply additional duties or adjust obligations equitably.
The principal Roman contracts recognized as bonae fidei included sale (emptio venditio), hire (locatio conductio), mandate (mandatum), partnership (societas), deposit (depositum), loan for use (commodatum), and guardianship (tutela). Stricti juris contracts, by contrast, included the stipulatio and the mutuum.
Why It Matters in Research
This term is primarily a term of Roman and civil law, and researchers will encounter it most often in historical sources: civilian treatises, early equity jurisprudence, and commentary on the development of English contract doctrine. Its importance to common law research is indirect but genuine — the distinction between bonae fidei and stricti juris contracts is foundational to understanding how equity courts justified intervening in contracts where strict legal rules produced harsh results, and how good faith obligations entered the common law through the back channel of equity.
Researchers working in early American or English contract cases should note that judges and treatise writers sometimes invoked this Roman distinction to explain why courts of equity could imply terms, relieve against forfeitures, or award damages beyond the literal agreement. The language appears more frequently in scholarly commentary than in judicial opinions, but its conceptual shadow is long.
The term also appears in comparative law and conflicts-of-law contexts, particularly when courts or scholars were tracing the lineage of implied duties of good faith in contract — a lineage that runs through the civil law systems of Louisiana, Quebec, and the continental European codes into modern debates about good faith in the Uniform Commercial Code and the Restatement (Second) of Contracts.
Researchers should be alert to the fact that the phrase bona fides and the phrase bonae fidei are used in overlapping but distinct ways in historical sources. Bona fides refers to the general quality of good faith; bonae fidei (genitive) describes the class of contracts governed by that standard. The distinction matters when parsing a source closely.
Historical Dictionary Support
Rapalje & Lawrence define contractus bonae fidei as contracts in which "the judge was not confined to the strict words of the contract, but could take into consideration all the circumstances of the case, and decide according to good faith and equity." They contrast this with stricti juris contracts and identify the same list of Roman contractual types as falling within the bonae fidei category.
Rapalje & Lawrence capture the doctrinal core accurately, consistent with the treatment in the major civilian authorities — Justinian's Institutes, and the civilian commentators who transmitted Roman doctrine into early modern legal scholarship. What the historical dictionary entry does not address is the subsequent migration of this concept into common law equity doctrine or its relevance to the good faith debates in modern American contract law. For those dimensions, the researcher must move beyond the dictionary to treatises on equity jurisprudence and the scholarship surrounding UCC § 1-304.
Jurisdictional Note
The term has no direct operative force in modern common law jurisdictions, where it functions as historical and comparative vocabulary rather than as a rule of decision. Its greatest continuing doctrinal relevance is in mixed civil-common law jurisdictions — particularly Louisiana — where good faith obligations in contract retain explicit civilian foundations.