One of the major uses to which the stipulatio was put in Roman law was in providing for a penalty payable if a party did not perform an obligation to which it was bound, a use encouraged by Justinian.17 Such a function of the stipulatio was especially useful given that specific performance of a contract could not be compelled; instead, the stipulatio was used as a means to encourage performance, including performance to a third party (again, especially useful given the absence of a general doctrine of third party rights in contract) and adherence to an arbitrator’s decision (against which no appeal lay).18

It has been said of the stipulatio that ‘its usefulness and flexibility made it the cornerstone of the Roman contractual system’.19 The prominence of this promissory action assured it a continuing role in later European legal thinking through the reception of Roman law into the later European ius commune.20 However, despite relaxation of its attendant formalities, it did not develop into the general contractual action of the later law; for that, recourse was had to Roman law’s consensual contracts. One further thing which the stipulatio did was to endow, in due course, the general law of contracts with the notion of causa which had been employed in relation to the stipulatio: in the medieval law, as is discussed later, the idea of causa was used to clothe bare pacts and thus render them enforceable in a way that had not been so in Roman law, given the rule ex nudo pacto non oritor actio.

(b)  Informal contracts

Informal contracts in Roman law were of two types: those binding upon consent (the ‘consensual contracts’ which were to provide the theoretical basis for the modern law of contract), namely sale (emptio venditio), lease/hire (locatio conductio), partnership (societas), and mandate (mandatum); and those binding only on delivery of a thing (the ‘real contracts’, or contracts re), namely the loan for consumption of money or another commodity (mutuum), the loan for use (commodatum), pledge (pignus), and deposit (depositum).21 There was some interaction between the formal and informal contracts, because, for instance, if parties wished to add to the default duties of the parties under one of

17 Inst. 3.15.7. 18 C. 2.55.1. 19 Zimmermann, Law of Obligations, p. 89.

20On which process, see generally Cairns and du Plessis, The Creation of the Ius Commune.

21Barter was originally unenforceable, but was given legal recognition towards the end of the classical period.

the informal contracts they might do so by embodying further duties in a stipulatio.22 Moreover, sometimes the potential of the informal and formal contracts taken together offered a number of possible means for effecting a certain type of transaction: thus, a gift might be effected by way of a stipulatio donationis or simply by delivery of the subject of the gift.23

Taking together the scope of both the informal contracts and the ­formal contracts considered in the previous section, a number of arrangements still remained unenforceable, these being the bare contract and bare unilateral promise (‘bare’ in the sense of not being clothed in any particular form). The bare contract, or nudum pactum, was to remain unenforceable until the medieval period, when the attitude expressed by the maxim ex nudo pacto non oritor actio gave way to that of pacta sunt servanda. Though the bare unilateral promise (promissio) was unenforceable, an exception was made in respect of a promise made to a municipality to support public works or in gratitude for some honour received (the pollicitatio).24

(c)  Conclusion on Roman law

The above analysis of the role of promise in Roman law discloses that the idea of promise featured in two main ways:

(1)It formed the basis of the most important formal contract, the stipulatio, a formal promise to another person of variable content, this contract undergoing some substantial development over the period of Roman law’s history. Such development allowed it to be used as a means of embodying any contractual undertaking, albeit eventually in the somewhat restricted form of a written undertaking. It could, for instance, be used to effect the gratuitous transaction of donation. As the stipulatio both embodied a gratuitous undertaking by one party to another, but also took the form of question and answer demonstrating the agreement of the parties, the stipulatio was at one and the same time gratuitous and consensual in nature. The permissibility of making conditional stipulations allowed the stipulatio to effect mutual undertakings.

22Johnston, Roman Law in Context, p. 78.

23And, indeed, by the Justinianic period, a mere contract of donation (pactum donationis) gave rise to a personal action: Inst. 2.7.2.

24D. 50.12.