Content and Classification of Contracts

It should be noted at the outset that no general definition of contract is found in the sources—only an enumeration of the ways in which a contractual obligation arose.

In contrast to modern law where, if certain conditions are met, an agreement to perform engenders a legally enforceable obligation, Roman law construed the agreement (conventio, pactum) as only invoking an obligation if the agreement could be classified, on the basis of its form or content, into one of the categories deemed capable of supporting an actio in personam. In other words, in order to be enforceable as a contract there was the further requirement that the agreement had an element referred to as causa contractus or reason for the contract. Four such causae were recognized and in each case a limited number of agreements, involving the requisite causa, formed a contract and gave rise to a legally enforceable obligation or obligations. The four causae and, consequently, the four categories of contractus were: (a) contractus re, i.e. contracts that were constituted by agreement and the transfer of a thing; (b) contractus verbis, i.e. contracts that were constituted by agreement and the use of certain formal words; (c) contractus litteris, i.e. contracts that were constituted by agreement and formal writing; and (d) contractus consensu, i.e. contracts constituted by agreement without anything further.^[581] Although the last category forms an exception to the Roman law approach described above, only four contracts could be concluded by mere agreement between the parties.

Contracts (and quasi-contracts) can further be classified into unilateral and bilateral or ‘synallagmatic’. A unilateral contract was one in which only one duty of performance was imposed on one of the contracting parties, whilst the other party had a personal right correlative to it. For example, in a loan of money the borrower alone was bound. On the other hand, a bilateral or synallagmatic contract occurred in cases where reciprocal rights and obligations arose.^[582] This kind of contract imposed duties on both the contracting parties, who also had personal rights correlative to the duties involved against each other. The aim of bilateral contracts was an exchange of performances as, for example, in the case of purchase and sale or of letting and hiring.

Within certain limits any act or omission could form the content of a contract. With respect to the object of a contractual obligation, the terms dare, facere and praestare are encountered.^[584] In a broad sense, dare meant giving or handing over a thing for the purpose of making the receiver the owner thereof; facere denoted doing something and also encompassed refraining from doing something; praestare originally meant to bind oneself as surety, to be responsible for certain duties arising from contractual obligations in certain circumstances, but was also used in the wider sense of performing. For the sake of convenience, the content of a contract may generally be described as the ‘performance’. Such performance could be specific or determined (certum), or not specific or undefined (incertum). It could also assume the form of an alternative, facultative or generic performance. In the first case, later termed obligatio alternativa, two or more performances were due but the creditor was entitled to only one of them. Unless otherwise agreed, the debtor could choose which performance to deliver.^[585] A facultative performance (obligatio facultativa) occurred when only one performance was due but the debtor had the capacity (facultas) to make another specific performance in the place of the original one.

The judicial proceedings for pursuing enforcement of the obligations arising from contracts could be iudicia stricti iuris, i.e. proceedings arising from a juristic act of the strict and formalistic ius civile (negotium stricti iuris) and introduced by an actio stricti iuris; or iudicia bonae fidei, that is, proceedings arising from so- called negotia bonae fidei and introduced by actiones bonae fidei^[586] In the category of negotia stricti iuris fell all unilateral contracts that bound the promisor to the exact performance of that which he promised, neither more nor less.^[587] The negotia bonae fidei, on the other hand, originated from the ius gentium and required the parties to perform their obligations in accordance with the requirements of good faith. In this category fell all bilateral contracts in which the parties were bound to perform whatever could be fairly and reasonably required according to the circumstances of the case, which may be either more or less than what was actually promised. Negotia bonae fidei (such as the contracts of sale, exchange, hire and partnership) always operated to impose certain duties on the parties, irrespective of whether or not such duties were expressly promised.

4.3.2