The Law of Contracts

As already noted, in Roman law contract (contractus) denoted a legal act based on an agreement by the parties to create a binding obligation.

3.4.1.1     Real Contracts

The real contracts (contractus re) were contracts that were constituted by agree­ment and the transfer of a thing (res).

The oldest real contract was mutuum, a gratuitous loan for consumption of money or other things that were weighed, numbered or measured (such as wine, oil, corn, gold or silver).^[370] A strict contract (negotium stricti iuris) dating from the third century bc, it was constituted by agreement and the transfer of property to another person, on the understanding that the borrower would at a later stage return the exact equivalent of what was lent.^[371] The contract was unilateral since only the borrower was bound and became operative when the money or other things were transferred to the person to whom the loan was granted.

The contract of commodatum or loan for use was established when one person lent an object free of charge to another, usually for a fixed period of time and for a specified purpose.^[374] This type of contract was introduced by a praetorian edict in the first century bc and was considered to be a negotium bonae fidei. As in the case of mutuum, commodatum was constituted by agreement and the transfer of an object. Otherwise than in mutuum, however, the borrower in commodatum did not acquire ownership but only detention (detentio) over the thing transferred. Thus, he would not suffer the loss if the object were destroyed or damaged unless he had failed to show the degree of care deemed appropriate. Commodatum may be described as an imperfectly bilateral contract: while in principle it invoked only one obligation (the duty of the borrower to return the same object to the lender after use or at a definite date), a contingent duty might also exist on the part of the lender under certain circumstances. The creditor (i.e. the lender or commodator) could enforce his personal right by means of a personal action known as actio commodati.

The contract of depositum came to the fore when one person (the depositor) handed over a movable thing to another (the depositarius) and the latter undertook to retain the thing in his safe-keeping gratuitously for a given period of time or until the depositor demanded its return. Like the commodatum, depositum derived from the ius honorarium and was therefore a negotium bonae fidei. It was constituted by agreement and the actual delivery of the thing.^[375] Such delivery caused only physical control or detention (detentio) to pass to the depositarius, while ownership and protected possession remained with the depositor. The depositarius could keep the thing but was not entitled to use it; if he did use it, he could be guilty of theft of the use of such thing, unless he had acted in good faith. As in the case of commodatum, depositum was an imperfectly bilateral contract: although in princi­ple such a contract only created one obligation, under certain circumstances it was possible for a counterclaim to arise. The principal obligation was always the duty of the depositary to return the thing on demand to the depositor in as good a condition as when he received it, together with any produce or accessories. If he failed to do so, the depositor could enforce this obligation by means of the actio depositi. On the other hand, the depositary could institute the actio depositi contraria against the depositor for compensation of expenses incurred by him in the maintenance of the object in question or for damage he had suffered as a result of mala fides on the part of the depositor.

As previously noted, pignus or pledge was a form of real security that was established when a debtor or third party handed over a corporeal thing to the creditor as security for a debt on the understanding that the creditor would return the property when the debt was duly paid. The agreement between the debtor or third party and the creditor pursuant to which the security was given constituted a contractus re insofar as the transfer of possession constituted the causa (re) of the contract of pignus. Like the contracts of commodatum and depositum, pignus was an institution of the ius honorarium and based on bona fides. Furthermore, pignus was an imperfectly bilateral contract that gave rise to rights and obligations in respect of both the pledgor as well as the pledgee. As long as the pledged object remained in his possession, the pledgee was in principle not allowed to use it unless expressly authorized by the contract. If he did so in bad faith, he could be found guilty of theft. But the principal obligation of the pledgee pertained to his duty to return the pledged thing in a proper condition as soon as the debt was extinguished.

3.4.1.2     Verbal Contracts

Verbal contracts (contractus verbis) were contracts that were constituted by agree­ment and certain formal words. Sponsio, the earliest verbal contract, is believed to have had a religious origin (it probably began as an oath). Later this contract was superseded by the stipulatio, one of the most important juristic acts known to Roman law. Both sponsio and stipulatio were institutions of the ius civile and therefore negotia stricti iuris.

Stipulatio was a unilateral contract that could be employed in various ways in private or procedural law. It consisted essentially in a formal question by the creditor/promisee (stipulator) containing the terms of the proposed promise and a positive reply by the debtor/promisor (promissor) accepting them. The same verb had to be used in both the question and the answer, such as “spondesne centum dare?” (“do you solemnly promise to pay one hundred?”)—“spondeo” (“I prom­ise”).^[379] As this suggests, stipulatio could only be concluded where the parties were in each other’s presence and where the promisor responded positively to the whole question without delay and without qualifying his promise by making it subject to a condition or time clause.

As stipulatio was a stricti iuris contract, the parties were supposed to mean what they said and only what they said. Hence it was difficult to imply unspoken terms. Furthermore, the promisor was still bound even if he had entered the contract as a result of fraud or duress. However, in the later republican era the praetor intervened to improve this unsatisfactory situation and gave the person who incurred financial loss as a result of duress an action (actio metus causa) for four times the value of the loss. He also granted a special defence of duress (exceptio metus) if the wronged promisor was sued. Furthermore, the action for fraud (actio de dolo) was made available to the person who had been conned into making a legally binding promise. This action could be employed only if there was no other remedy and was directed at compensation for the actual loss suffered. The defrauded promisor was also given the exceptio doli as a defence against an action aimed at enforcing the contract. When the relevant transaction had been executed and loss had already been suffered, the praetor could restore the injured party to the position he would have been in but for the duress or fraud (restitutio in integrum).

Not all stipulations were valid. A promise to perform something that was illegal, immoral or physically impossible was void. Moreover, stipulations intended to take effect only after the death of one of the parties were deemed impossible and therefore void. It should be noted, further, that when performance became impos­sible after the conclusion of the contract, the debtor was in principle discharged from liability. In time, however, a clause was implied by which the debtor under­took that performance would not become impossible owing to his own actions.

Stipulatio was the most important contract in Roman law because it was not confined to particular transactions but could be used to render any kind of lawful performance binding. For instance, this form of contract could be employed for the transfer of ownership over a sum of money or some other object; the carrying out of certain work; the constitution of a dowry; the establishment of certain rights on another’s property; the transformation of an existing obligation into a new one (novatio); and various kinds of promises in the course of judicial proceedings. Moreover, it could be employed to cover all the terms of another type of contract, e.g. sale (in which case the contract was one of stipulatio),^[382] or some terms of another contract, such as warranties against eviction and latent defects in sale. An important application of the stipulatio was as personal security, whereby the guarantor promised to pay the same or a lesser debt as the principal debtor, and the creditor could exact from either. The earliest forms of suretyship by stipulatio in Roman law were sponsio and fidepromissio, which were distinguished by the form of words employed by the stipulator-creditor in addressing the intended surety. However, both were subject to a number of limitations: they could only be employed when the principal obligation itself was created by stipulatio; the obli­gation of the surety died together with the person who undertook it and, in all cases, was extinguished 2 years after it was established; and where there was more than one surety for the same debt, each was liable only for his pro rata share of the debt, even if one or more of his co-sureties were insolvent. These limitations, although largely beneficial to the surety, restricted the scope and usefulness of sponsio and fidepromissio thereby rendering them unattractive to creditors. Thus, during the later republican age fideiussio emerged as a third form of suretyship that was also created by stipulatio and not subjected to any of the above-mentioned limita- tions.^[383] This form of suretyship, available to both Roman citizens and foreigners (peregrini), gradually superseded the two older forms and evolved as the only form recognized in the time of Justinian’s reign.

In early law, performance did not discharge a contract. There had to be a formal verbal acknowledgment of performance, in this case called acceptilatio. The stipulatory debtor formally asked his creditor whether the latter had received performance (habesne acceptum?), and the creditor formally answered that he had (habeo). In the classical period, however, performance by itself had become sufficient, and acceptilatio was simply a method of release (when the parties agreed) without performance, the acknowledgment being fictitious.

There were two other forms of contractus verbis recognized by Roman law: dotis dictio and iusiurandum liberti. The dotis dictio was a method of constituting a dowry (dos) by means of a unilateral promise expressed in prescribed words by the donor (the wife, her pater or one of her debtors) and delivered in the presence of the husband.^[384] The iusiurandum liberti was a solemn promise by which a manumitted slave assumed the duty to render certain services to his patron. Since a slave could not bind himself by a civil law contract, and could refuse to do so after his manumission, his undertaking was usually secured before he was freed by an oath and this created a religious duty for him. After his manumission the iusiurandum liberti was employed to produce a civil, contractual obligation. This type of contract still existed in the time of Justinian’s reign.

3.4.1.3     Literal Contracts

Literal contracts (contractus litteris) were contracts constituted by agreement and a certain form of writing. Much of the detail is uncertain, but it is clear that this contract was a contract of strict law (negotium stricti iuris) created by an entry (nomen transcripticium) in a creditor’s ledger or account book (codex accepti et expensi) of a fictitious payment to a debtor.^[385] There were two entries (transcriptiones) of this nature: a re in personam and a persona in personam. The first occurred when an existing debt between the parties was entered and thereby transformed into a new debt based on a contractus litteris.^[386] The second came to the fore when a debt still due was entered as discharged and an equivalent sum was entered as being owed by another person who thus became liable for the debt of the former debtor. This might incidentally also have the effect of transforming an earlier obligation into an obligation litteris, but its primary purpose was to substi­tute one debtor for another. As the above description suggests, the contractus litteris was in essence a form of novation (novatio) whereby one obligation was terminated and superseded by another.^[387] As compared with stipulatio, this form of contract was very limited in scope (it was available only for money-debts) but had an important advantage: it could also be concluded inter absentes. The form of literal contract based on the nomina transcripticia was the only written contract known to Roman law. It presupposed a special system of book-keeping, and when this system fell into disuse in the third century ad the literal contract disappeared.^[388]

3.4.1.4     Consensual Contracts

Consensual contracts (contractus consensu) were contracts constituted by the mere agreement (consensus) of the parties. These contracts were binding as soon as the parties agreed on the basic essentials of the contract. Unlike the other categories of contract, no further formalities were required such as the transfer of a thing, formal words or writing. According to both Gaius and Justinian, there were four types of consensual contract: purchase and sale (emptio venditio), letting and hiring (locatio conductio), partnership (societas) and mandate (mandatum). These forms all orig­inated from the ius gentium and were, therefore, negotia bonae fidei.¹⁴⁴

Emptio Venditio

The contract of purchase and sale (emptio venditio) was a bilateral contract whereby one person promised to transfer to another a certain thing (merx) and the other on his part promised to pay a price (pretium). No set formalities were legally required, but for important transactions evidence could be provided by writing or by giving earnest money (arra), which could also serve as part payment. The giving of arra was not required for the conclusion of the contract, although the parties could insist on this practice. However, in later law arra assumed a greater significance. Thus, Justinian stated that if arra had been given and the buyer then refused to complete the contract he forfeited it, while the seller who repudiated the contract was bound to restore the arra and pay the same amount in addition.^{[389] [390]} Furthermore, it was recognized that where the parties agreed that the contract was to be put into writing, there was no contract until the relevant document was completed and formalized, and either party could withdraw without penalty provided that no arra had been given.

Since agreement was essential to the contract of sale, an error that negated agreement prevented the contract from coming into being. Such error was sufficient if, for instance, it was about the nature of the legal transaction entered into (error in negotio), or about the identity of the object of the contract (error in corpore). A controversial type of mistake was the so-called error in substantia, a mistake about a material characteristic of the object of the contract—for example, the purchaser believed that the item he was buying was composed of gold, but it turned out to be of copper. It was recognized that a mistake of this kind would nullify the contract only if the object at issue differed so widely from what it was supposed to be that it fell into a distinct commercial category. Finally, reference may be made to error in pretio or mistake as to the price of the object of the contract, and error in quantitate or mistake regarding the quantity of the contractual object. Such mistakes were only partially operative: neither party could enforce the relevant contract at his own figure; but each could, if he so wished, enforce it at that figure of the other.

The object of the contract of sale (res or merx) had to be specific (certum), in existence or capable of existing and legally capable of being the subject of com­mercial transactions (res in commercio).^[391] Any clearly defined thing or even a complex of things or assets (e.g. an inheritance), a right or a servitude, could be the object of a sale. Moreover, for a contract of sale to be valid the price (pretium) of the object sold had to be fixed (certum) and it had to be seriously intended (a disguised gift was not a sale).^[392] It was required, further, that the price should consist of money (in pecunia) as otherwise it would be impossible to distinguish sale from exchange or barter^[393] as well as buyer from seller (their duties being different). In classical law the principle of free bargaining prevailed and so the amount of the price was left to the unfettered discretion of the parties concerned—the law did not intervene to dictate how they should draw up their sale agreement.^[394] However, post-classical law developed the so-called laesio enormis (‘enormous loss’) rule: if land had been sold at less than half its actual value at the time of the sale, the seller could cancel the contract, return the price paid and claim back the land, unless the buyer made up the price to the full value.^[395]

The principal duty of the buyer was to pay the agreed price to the seller. In principle, this had to be done on the day of delivery of the object sold, although the parties could agree otherwise. The buyer had to reimburse the seller for expenses incurred by the latter in looking after the thing during the period between the conclusion of the contract and delivery. Moreover, he was liable to pay interest if he had fallen into default (in mora) by failing to render payment on the date specified in the agreement. The seller’s duties were more complex. He had to keep the thing sold safe until delivery; give free and undisturbed possession of the thing to the buyer; and provide guarantees against eviction and hidden defects. If the seller was himself owner of the thing sold, the contract of sale was regarded as a iusta causa traditionis and in classical law the ownership of the thing passed to the buyer on delivery.^[396] On the other hand, where the seller was not the owner of the thing the principle applied that no one could transfer more rights to another which he himself had not possessed (nemo plus iuris ad alium transferre potest quam ipse haberet). This meant the buyer did not acquire ownership, although the possibility of acquisition of ownership by usucapio remained open. Where the thing sold belonged to a third party, that party could institute the rei vindicatio against the buyer to assert his ownership and evict the buyer from the thing. In such a case, the buyer could institute the actio empti for damages but only in the case where the seller had fraudulently sold the thing of a third person. In other cases the buyer had to bear the loss. In the course of time, however, it became customary for the buyer to take a stipulation that his use and enjoyment of the object sold would not be legally disturbed, and by a series of steps that culminated in the second century AD this guarantee came to be implied in the sale. Besides an implicit guarantee against eviction, Roman law also recognized the existence of an implicit guarantee against hidden defects, i.e. defects that rendered the thing sold unfit for its ordinary or contemplated purpose. Regarding this protection measure, the law also went through a long process of evolution. In early law, the buyer was not protected against the presence of latent defects unless the seller had fraudulently (dolo malo) omitted to disclose a defect known to him but of which the buyer was unaware. In the course of time it was recognized that the parties could enter into stipulationes whereby the seller guaranteed that the object being sold was free of certain defects or endowed with certain features. In the late republican era the aediles curules, who had control over the streets and markets, introduced special provisions in their edict requiring sellers of slaves as well as beasts of draught and burden to publicly disclose certain temporary or permanent physical and mental defects. If the seller failed to declare any of these defects, the buyer had a choice of two aedilician actions: the actio redhibitoria and the actio quanti minoris. By means of the former action, the buyer could demand rescission of the sale, return of the purchase price by the seller and the restoration of the thing by the buyer. The latter action pursued affirmation of the sale and restitution of the difference between the price paid and the actual value of the defective slave or animal.^[397] Over time the aedilitian remedies were extended to sales of slaves and draught animals outside the market, and by the time of Justinian’s reign they encompassed sales of every kind including land. At the same time, a warranty against latent defects came to be implied in all sales.^[398]

Locatio Conductio

The contract of letting and hiring (locatio conductio) or lease was a bilateral contract concluded when one person (the lessor or locator) had consented to give another (the lessee or conductor) the use and enjoyment of his thing, services or labour and the latter on his part had consented to pay remuneration. As in the case of the contract of sale, locatio conductio developed from the ius gentium and was therefore based on bona fides. A contract of lease became valid and binding as soon as the parties had reached agreement on three essential elements: to let and to hire, the subject matter and the price. No formalities were legally required, and the requisite agreement could be reached in any manner (e.g. by letter or through a messenger). With respect to the subject matter of the contract, a distinction is made between three types of locatio conductio: locatio conductio rei; locatio conductio operarum; and locatio conductio operis.

Locatio conductio rei was a contractual agreement whereby the lessor agreed to allow the lessee the use and enjoyment of a particular object for a fixed period of time or in perpetuity. If the object was not fit for the purpose of the lease, the lessor was absolutely liable for return of rent and damages irrespective of whether he knew of the defects or not. Where the lessee suffered damages or was prevented from use and enjoyment of the thing let owing to fraud or negligence on the lessor’s part, the lessee could institute the actio conducti and hold the lessor liable. Fur­thermore, the lessor bore the risk if the lessee was prevented from using and enjoying the object leased due to an act of God (vis maior). In such case the lessee was released from his obligation to pay rent and the lessor was obliged to restore the amount of the rental he had already received.

Locatio conductio operarum was an agreement whereby one person consented to place his services (operae) at the disposal of another person, and the latter on his part consented to pay remuneration. The person letting his services was therefore the lessor (locator) and could claim his wages by means of the actio locati; the person employing such services was the lessee or hirer (conductor), and could claim the services by means of the actio conducti. Hire of services was not as common as it is in present-day law since most labour was performed by slaves, and when the services of another’s slave were hired this would usually be hire of a thing (locatio conductio rei).

The contract of locatio conductio operis came to the fore when one person assumed the duty to perform a specific task or work for another person who had placed such work out on contract and consented to pay in return. In this context, the object of the contract was not services for a limited time but the completion of a piece of work, such as the manufacturing of an object from material supplied by the employer; the building of a house; the cleaning or repairing of clothes; the training of a slave; the teaching of children; or the transport of goods or persons. The party contracting to perform the work was the lessee or contractor (conductor), while the party commissioning the work was the lessor (locator). The contractor had the duty to produce the specified result (opus facere). If he failed to do so due to his own negligence or fraud, he was liable for damages by way of the actio locati. Further­more, the contractor was liable for the loss of or damage to things that had been entrusted to him by the locator, even if he were not negligent, unless the injury was the result of external force (vis maior).

Societas

The contract of partnership (societas) was concluded when two or more persons had reached an agreement to pursue a common purpose with the use of common resources. Partnership had its roots in the early Roman institution of consortium ercto non cito (partnership by undivided inheritance), i.e. the community of sui heredes who decided to administer the estate of the testator jointly, but not as a result of contract. When consensual partnership emerged during the republican era, the standard case was partnership of all the assets of the partners (societas omnium bonorum), in which all partners’ current and future property became joint property or part of a common pool. Other forms of partnership were the societas alicuius negotiationis, in terms of which the purpose of the partners was to engage in one particular kind of business venture (e.g. the transportation of commodities)^[399]; and the societas unius rei, concerned with the exploitation of a single joint asset (e.g. a racehorse) for common benefit. Each partner was required to contribute something, whether labour or assets, and each had the right to some share of profits. Unless the partners agreed otherwise, they shared profits and losses equally. They were also liable to each other but only for fraud, since it was regarded as a partner’s own fault if he chose a negligent partner.^[400]

The societas, even in its classical form, had no legal personality.^[401] This meant the partnership could not be the owner or possessor of property, debtor or creditor and neither could it litigate, buy or sell, hire or let and such like. Furthermore, a partner had no implicit authority to bind his fellow partners even in matters closely connected with the business of the partnership. Thus, when a partner entered into a legal act with a third party he alone was affected by such act and thus became liable to or acquired rights against the third party. Normally, however, the partners were both entitled and bound to bring their dealings with third parties into the partnership account. Thus, when a partner’s share in the profits or losses of the partnership was calculated, the rights and liabilities arising from all his individual transactions were taken into consideration.

A partnership could be dissolved in a variety of ways: by a unilateral express declaration to this effect by one of the partners (ex voluntate)^[402]; if the period agreed upon expired; if the goal for which it was formed had been accomplished or became impossible; or if the communal property was lost or an essential asset passed out of commercium. Moreover, since the relationship between the partners was highly personal, the partnership was dissolved by the death of one of the parties.^[403] The capitis deminutio or insolvency of a partner or the forfeiture of a partner’s entire estate also entailed the dissolution of the partnership.^[404] After the termination of the partnership the partners could institute the actio pro socio against one another or, where applicable, the actio communi dividundo for the liquidation and division of the common property.

Mandatum

Mandate (mandatum) came to the fore when an agreement was reached whereby one person (the mandator) gave another person (the mandatary or mandatarius) a commission to do something gratuitously for him, and the mandatary accepted the commission.^[405] If the undertaking was to enter into a contractual relationship with a third party, then any resulting contract was between the third party and the man­datary. Hence mandate was not direct agency. The principal duty of the mandatary was to carry out the mandate properly and to hand over to the mandator all benefits he acquired during its execution. If the mandatary did not comply with his obliga­tions, he could be sued by means of the actio mandati. Occasionally, the mandatary incurred certain expenses or suffered loss or damage in the performance of the mandate. Provided that these expenses were necessary and he had not exceeded the mandate, he could institute the actio mandati contraria against the mandator to claim reimbursement of expenses or damages. As the mandatary was originally considered to be a trusted friend performing a gratuitous service, he was normally liable only for fraud (dolus). The contract of mandate was terminated when the mandate had been carried out or when the prescribed time period for its perfor­mance had elapsed. Furthermore, either party could revoke the contract provided that execution of the mandate had not yet commenced.

name=bookmark1321>3.4.1.5     Innominate Contracts

As previously observed, Roman law recognized only a limited number of contracts. Although any lawful undertaking could be made binding by means of stipulatio, some common daily transactions that fell outside the normal categories of contracts were gradually rendered enforceable. The term ‘unnamed’ or ‘innominate’ con­tracts (contractus innominati) was later introduced by jurists to describe enforce­able agreements for reciprocal performances which, unlike the recognized types of contract, did not have a name of their own. The most common examples of unnamed contracts encompassed exchange or barter (permutatio) whereby the parties agreed that each would transfer something to the other in ownership (e.g. an ox for a horse); the agreement of hawking (aestimatum), whereby the owner of goods handed them over to another person on the understanding that the latter would, within a prescribed period of time, either return the goods or pay the sum agreed upon to the former, while retaining any profit he may have obtained from selling them^[406]; and the precarium, a gratuitous grant of the enjoyment of a thing revocable at will.

The contractus innominati were regarded as informal, legally unenforceable agreements (nuda pacta) from which no obligations arose. If, however, one of the parties had already performed his side of the agreement and the other party did not reciprocate, the former party could in certain cases recover his own performance by means of a legal action (condictio ob causam datorum). However, he had no legal action by way of which he could compel the other party to render performance. To address the potential injustice that might arise from this event, the praetor granted in certain cases an actio in factum^[407] whereby the party who had already performed could force his opposite number to carry out his part of the agreement. By the time of Justinian’s reign, this praetorian arrangement was broadened in scope so that a legal action (the actio praescriptis verbis) became available in all cases involving a bilateral transaction for reciprocal performances that did not conform to the typical and recognized categories of contracts. This general bonae fidei action could be adapted to different legal situations in which a party who had honoured his undertaking claimed performance of the reciprocal duty by the other party.

3.4.1.6     Quasi-Contracts

Justinian grouped together a number of situations akin to contract that gave rise to legally enforceable obligations ‘as if from contract’ (quasi ex contractu). Some of these were analogous to particular contracts, while others resembled contracts only in that they did not arise from delicts.^[408] The most important quasi-contracts were unauthorized administration (negotiorum gestio) and undue payment (solutio indebiti). These quasi-contracts arose not from an agreement between parties but from a performance by a person that entailed rights for that person and corresponding duties for another.

Negotiorum gestio came to the fore when one person (negotiorum gestor) rendered a service to another (dominus negotii) without prior authorization or agreement.^[409] The service performed might be of any kind: a factual act, a legal act, a single act (e.g. the repair of a building) or a general administration of another’s affairs (e.g. becoming a surety), as long as it was not illegal, impossible or immoral. The gestor had to have the intention to manage another’s affairs and act on the expectation that he would have a legal claim to an indemnity.^[410] Negotiorum gestio was an imperfectly synallagmatic or bilateral legal act that originated from the ius honorarium and was therefore based on bona fides. The dominus could institute the actio negotiorum gestorum directa against the gestor to claim recovery of the proceeds derived from the negotiorum gestio and damages caused by the latter’s fault. On the other hand, the gestor had recourse to the actio negotiorum gestorum contraria whereby he could claim compensation for necessary expenses he incurred or loss or damage he suffered in the execution of the task.^[411]

Undue payment (solutio indebiti) occurred where a person paid in error what he was not obliged to pay.^[412] In such a case, the law laid a duty of restitution upon the person who received payment. Recovery of such payment could be obtained by means of a special personal action, known as condictio indebiti. For the successful institution of this action the plaintiff had to prove that he had bona fide erred and had performed while labouring under a mistake (per errorem).^[413] On the other hand, the person who received the money or other property also had to believe, bona fide, that the performance was due to him—otherwise he would be held to have committed theft (furtum).

3.4.2