Sources of obligations: contracts and delicts

Probably based on the Aristotelian distinction between voluntary and invo­luntary activities, Gaius in his Institutes (3.88) introduced a primary division of the sources of obligation: all obligations arise either from contract (ex contractu), i.e., an enforceable agreement, or from delict (ex delicto), i.e., a wrongful conduct.

A legal elaboration of the idea of contract took place in the later Republic. Servius Sulpicius used the noun contractus in relation to betrothal (Aulus Gellius 4.4). Labeo’s attempt to restrict the concept of contract to bilateral agreements was probably isolated, but it cannot be underestimated (Ulpian- Labeo, D. 50.16.19). Labeo identified the Latin contractus with the Greek synallagma and therefore considered contractual only those obligations in which the parties were mutually obliged (ultro citroque obligatio). Later, the jurist Pedius (Ulpian-Pedius, D. 2.14.1.3) acknowledged that every contract is founded on an agreement: “There is no contract, there is no obligation which does not contain in itself an agreement.” From Gaius’s time onward, contract meant an enforceable agreement in accordance with civil law. Originally, informal nonenforceable agreements were called pacts (pacta), but with the recognition of some enforceable pacts, the distinction between pacts and contracts became confused and meaningless. I use the term “contract” according to Gaius’s broad conception, although I am aware of its limitations: Gaius’s approach was unfamiliar to classical jurists, and he was rightly considered a pre-postclassical jurist. His doctrine, however, deeply influenced Justinian’s compilers and ultimately prevailed in the civil law tradition.

Different from contract was delict (in Latin delictum and sometimes maleficium). A delict was a wrongful conduct that caused harm to someone. As with contracts, the Romans did not elaborate a doctrine of delicts. Rather, they identified and regulated a series of individual delicts in both civil and praetorian law, and they protected the injured person with penal actions. Delicts were always private, unlike crimes, which were offenses punished by public criminal law. Redress of a delict had a penal character and was ordered originally by civil law. Gradually, however, the praetor established some redresses for situations not covered by civil law: the so-called praetorian delicts.

The dichotomy of contract/delict was not exclusive. Gaius (3.91) refers to a case of a payment that was not due but was made anyway - a payment that thus appeared to be founded neither on contract nor on delict. It is therefore not surprising that this famous dichotomy was partially altered by Gaius himself in his Res cottidianae sive aurea (D. 44.7.1pr.), a revised version of the Institutes attributed to him: “Obligations arise from contract, from delict, or by some provisions of law from various types of causes.” This text added a residual third category of obligations that embraced those that arose without agreement or wrong (e.g., a payment of money that was not due).

Justinian’s Institutes (3.13.2) offered a more detailed classification of the sources of obligations, basically following Gaius’s order. According to Justinian’s Institutes, obligations could arise from a contract (ex contractu), as though from a contract (quasi ex contractu), from a wrong (ex maleficio), or as though from a delict (quasi ex maleficio). Justinian’s compilers subdivided the “various types of causes” Gaius mentioned in Res cottidianae into those that were closer to contracts and those that were closer to delicts. Quasi contractual obligations included the payment of money not due (solutio indebiti) and the management of another’s affairs (negotiorum gestio). Their common denomi­nator was probably the existence of some kind of business without an agree­ment between the parties. Examples of quasi-delictual obligations were those derived from pouring or throwing things out of buildings and from stealing or damaging property entrusted to a sea carrier, innkeeper, or stable keeper, among others. The common denominator of quasi delicts was the imposition of liability regardless of fault.