The historical sweep of the present chapter is necessarily broad, given the antiquity of the influence of promissory ideas in the law. In consequence, much of the analysis is necessarily condensed in nature. There is, however, merit in such a broad historical view, given that prior analysis of the history of promise has tended to appear only as a small element in larger treatments of private law in general or of the law of obligations as a whole, while the present treatment seeks to take promissory developments as the sole focus of analysis. With this point in mind, it is to Roman law that attention must first be turned when explaining the role of promise in the contract law of the ius commune.

1.  Roman law

(a)  Formal contracts: the stipulatio

Classical Roman law was a law of actions and related rules rather than one of concepts or principles of general application. It had no general law of contract, and precious little contract theory.4 It did, however, as a result of the classificatory work of the jurist Gaius and later development, conceive of a central division in the law of obligations between those actions arising ex contractu (from a contract), ex delicto (from a delict), quasi ex contractu (as if from a contract), or quasi ex delicto (as if from a delict). It has been conjectured that Gaius may have developed this divisional scheme from his understanding of Aristotle, but that cannot be proved.5 In any event, the scheme itself, while one which allowed the pursuit of certain analytical goals by scholars, was not of much practical significance. What mattered in practice were the specific types of Roman contract, and the rules governing their use. It is within these specific contracts that the original influence of promise in Roman law may be seen.

The contracts recognised in Roman law were both formal and informal. Though the latter came to have the greatest significance for later contract theory, it is within the former that the promise took root. Formal contracts were those which were required to be made according to a specified formality in order to be valid. The formalities were simple and clear, and allowed for certainty in the undertaking of basic transactions. Formal contracts were either verbal (verbis) or written (litteris). An example of the latter was the insinuatio, a written contract, registered before a court,

4Gordley, Philosophical Origins, p. 30; Watson, The Law of the Ancient Romans, p. 58.

5See Gordley, Philosophical Origins, p. 31, citing German sources for this view.

by which a gift was effected. An example of the former was the stipulatio, a contract by which one party promised something to another. As both insinuatio and stipulatio demonstrate, in Roman law one must avoid the misconception that the essence of contract was in every case mutual performance: this was not necessarily the case, for both insinuatio and stipulatio were gratuitous in nature, one party alone undertaking a duty in favour of another.

The focus of the present analysis of Roman contract lies in the stipulatio­ , for it is in this action that one finds the enforcement of a promise. The promise itself might be of any nature whatsoever, a flexibility of content which made the stipulatio incredibly useful to parties. Any duty might be made enforceable in a stipulatio, so long as the promise was made in the correct form. This potential universality of content gave the stipulatio a flexibility comparable to modern contract law. Though a stipulatio required a valid supporting causa or purpose, such causa need not be mentioned in the verbal promise, so the promise might be framed either causally or abstractly.6 The undertaking of a stipulatio was achieved through a simple verbal exchange. The promisee (creditor) asked the promisor (debtor) whether he undertook the promise in question. Thus, for instance, he might ask ‘do you promise to pay a hundred [denarii]?’ (spondesne centum dare?), the promisor answering ‘I promise’ (spondeo). With the giving of the response, a stipulatio was immediately created, and no witnesses or recording of the act were required. The immediacy and simplicity of the binding effect of the undertaking was one of the benefits of the stipulatio.

It is striking that it is the promisee who frames the content of the promise to which the promisor is to give his simple, unqualified assent. This is quite different to modern promising, where it is the promisor who asserts what he is willing to promise with (in some systems) a simple acceptance required by the promisee. The result of the Roman process is, of course, that the obligation created by the stipulatio is a gratuitous one, the promisee coming under no mutual obligation. If a mutual arrangement were desired, then a stipulatio would have to be made by each of the two parties. This would open up the danger that the second intended promisor might not make his promise following the making of the first. That, ­however, could be accommodated, in later law, by both stipulators

6See Zimmermann, Law of Obligations, pp. 91, 550. A stipulatio was however required to have a causa, even if unexpressed. If the stipulatio was framed abstractly (without any specification of the underlying causa) then the failure of the underlying cause could be raised by the promisee by way of an exceptio doli: D. 44.4.2.3.

by way of written transaction, there being no formal oral requirements.11 However, an alternative view has been advanced that writing was never more than evidentiary, and that the essence of the stipulatio remained an oral undertaking, a position which finds support from some later Roman texts.12

By the Justinianic period, some discrepancies between question and answer were tolerated: for instance, a request for 100 sestertii, met with a promise to pay 500, would be interpreted as a promise good for the lesser amount, it being included within the greater amount; likewise if A promised the property Pamphilus, and B the properties Pamphilus and Stichus, there would be a good agreement for Pamphilus alone.13 This is not quite the modern law of offer and acceptance, where an offer met with a qualified acceptance can still be the basis of a contract by treating the qualified acceptance as a counter-offer; rather, on the Roman conception, the valid lesser undertaking was severable from the invalid greater.

By 469, the development of the stipulatio in its final form was complete, that year seeing the promulgation of a law of the Emperor Leo that

All stipulations, even if they are not expressed in formal or direct words, but in any words whatsoever, with the consent of the contracting parties, and they are in conformity with the laws, shall be valid.14

With such a development, Roman law dispensed with the need for the use of specific formal words for the creation of a stipulatio: any question and answer form might now be used as the basis of a valid stipulation.15 Though the parties still both had to be present at the time the stipulation was made, there was a presumption that they were present if that were represented to be the case, rebuttable only if it could be shown that the parties were not present in the same town on the day in question.16

11Zimmermann (ibid., p. 85) describes this change as having occurred under the influence of Hellenistic practice and tradition, citing Kaser, Das römische Privatrecht, pp. 76f, 376ff on this point.

12The debate is discussed by MacCormack, ‘The Oral and Written Stipulation in the Institutes’, who advances the alternative view. See also Nicholas, ‘The Form of the Stipulation in Roman Law’, who likewise maintains that in Justinian’s time writing remained merely ‘juridically evidentiary’. Meyer, Legitimacy and Law in the Roman World, argues (p. 264) that at the end of the fifth century ad there was evidence to suggest that the formal and ceremonial aspects of stipulatio were still being adhered to.

13 D. 45.1.1.5. See Johnston, Roman Law in Context, p. 77. 14 C. 8.37.10.

15See Nicholas, ‘The Form of the Stipulation in Roman Law’, p. 77.

16See the Law of Justinian of 531 to that effect, recited at C.8.37.14.