than that determined by the idea of consideration, thus permitting the enforcement of unilateral promises.

The doctrine of consideration was subtly different to the older common law idea of quid pro quo. Consideration was conceived of as the thing which motivated the giving of a promise,72 whereas such motivational criterion was not present in the idea of quid pro quo. Consideration, moreover, might be constituted not merely by a benefit to the other party, but could include a benefit conferred upon a third party, or the incurrence by the other party of a detriment.73 An undertaking to marry was good consideration, having formerly been, only by the turning of a conceptual blind eye, an act of reciprocity.

3.  The Northern natural law school

By contrast with English law, the contract law of Continental Europe and Scotland of the early modern period was the subject of a number of important theoretical treatments. The principal writers of the law in this period belong to what has been styled the Northern natural law school. It is their works which form the vast majority of the following discussion of this period, with an occasional reference to decisions of the courts.

The Northern natural law school were the last group of jurists to espouse unashamedly the natural law tradition of Aristotle and Aquinas, though as Reformed, early Enlightenment scholars, they did so from a Protestant perspective, and placed a greater emphasis upon reason than those natural lawyers who had gone before them. The greatest members of this school were the Dutchman Hugo de Groot (Grotius), the German Baron Samuel von Pufendorf, and the Scottish judge James Dalrymple, Viscount Stair.74 The writing of each of these men was characterised by a blend of natural law thinking and an early modern view of the importance of man as a rational being. The natural law and reason were seen as going hand in hand, the latter informing the former. Each of the three gave a prominent place to promise in his writings, though with Pufendorf we see the abandonment of promise as the central concept of the law of

72Ibbetson, An Historical Introduction, p. 144; Simpson, A History of the Common Law of Contract, p. 424.

73Ibbetson, ibid., p. 142.

74Other members of the School included: Petrus Gudelinus (1550–1619) of Leuven University; the French Huguenot translator of Grotius, Jean Barbeyrac (1674–1744); and the Scottish judge, Henry Home (Lord Kames, 1696–1782), Kames being one the last writers to merit the description of a natural lawyer in the ancient tradition.

obligations and its replacement with that of agreement. The writings of the Northern natural lawyers were to be influential in the development not only of modern civilian systems but also of the modern law of the mixed legal systems of Scotland and South Africa.

(a)  Hugo Grotius75

Hugo Grotius devotes a chapter of Book II of his work De jure belli ac pacis to promises.76 This title follows an opening chapter on the causes of war (identified as self defence and property) and a succession of chapters on matters concerning rights relating to property and persons.

It is notable that Grotius deals separately with promises,77 moving on to contracts,78 then oaths,79 before looking at all three as they relate to sovereign powers80 and treaties.81 Why does Grotius treat promises separately, and why does he place his treatment of promises before that of contract? He gives us little idea of the reasons for this in the chapter on promises itself, as he opens his chapter on promises by saying simply that the ‘order of our work has brought us to the obligation which arises from promises’.82 However, promise’s appearance before contract, and the fact that (unlike Pufendorf) he gives it a separate treatment, does give the impression of its holding a primacy in Grotius’s scheme of obligations. This may well be because Grotius saw himself as a scholar within the scholastic tradition, with all that that meant for the traditional scholastic emphasis of promises and vows.83

Grotius was not however a slave to scholastic opinion.84 He begins his discussion with a strong refutation of Connanus’s views that only reciprocated promises should be enforced and that it is not unjust not to fulfil a promise but only dishonest. Grotius cites in support of the contrary view, that promises ought to be honoured even when unreciprocated or not yet performed, the opinion of Hebrew jurists, passages of Paul from

751583–1645.

76The citations of the English translation of De jure belli ac pacis used are from the 1925 translation by Kelsey of the 1646 edition.

83See Zimmermann, Law of Obligations, pp. 567–8.

84He remarks of the scholastics that, because they lived in an age deprived of knowledge of the liberal arts, ‘it is less to be wondered at if among many things worthy of praise there are also some things which we should receive with indulgence’ (De jure belli ac pacis, Prologue, 52).

by way of exchange,92 an approach which does no more than pay lip service to Aristotle’s idea of commutative justice. Grotius is, however, well acquainted with Aristotle: he characterises human acts as either ‘kind’ or ‘reciprocal’, citing Aristotle, and the first chapter of his first book contains a lengthy discussion of Aristotelian classifications of justice and law.93 It is also more than abundantly clear that his text shows a clear support for natural law philosophy, though like Stair natural law and reason are inherently linked in Grotius’s view.94

The remainder of Grotius’s discussion of contract seems somewhat jumbled and disjointed, for he deals, in no apparent order, with a number of seemingly unrelated issues, such as the estimation of the price in a sale, monopolies contrary to nature, money as the medium of exchange, interest, partnership, joint undertakings for maritime operations, and a number of other topics. The result, for those looking for a logical treatment of the field, is unsatisfactory, far less elegant and structured than that of his treatment of promise, and certainly less satisfactory than the structured treatment offered by his near contemporaries Stair and Pufendorf.

A comparison of Grotius’s treatment of promise and contract is instructive. He stands as perhaps the last writer in the natural law tradition who gave promise a central role in obligations theory. With his passing, contract and mutuality were to replace promise and unilaterality as the central themes in the first treatments of obligations which ushered in the modern era of obligations theory. However, as will be seen, though mutuality was to become the dominant model, the idea of promise had become so entrenched that the conceptualisation of mutual agreement was still discussed in promissory terms.

(b)  Samuel von Pufendorf

At the cusp of this era of modernity stands another member of the Northern natural law school, Samuel von Pufendorf.95 Although he treats of promise in his writings, he gives it much less emphasis than did Grotius

92Ibid., II.xii.11.1: ‘Whatever, in fact, the parties promise or give, they should be believed to promise or give as on an equality with the thing which is to be received, and due by reason of that equality.’

93Ibid., II.xii.2.

94‘The law of nature is a dictate of right reason … an act, according as it is or is not in conformity with rational nature, has in it a quality of moral baseness or moral necessity; and that, in consequence, such an act is either forbidden or enjoined by the author of nature, God’ (I.i.10.1).

951632–1694.

classification – that between perfect and imperfect obligations – with examples of promises of both type. A perfect obligation is one which creates a legal entitlement to enforce the obligation; an imperfect obligation does not. Like Grotius before him, Pufendorf insists upon an acceptance on the part of a promisee before a promise may become perfect and thereby bind the promisor.103 This seemingly minor point is in fact of great significance. Because promises must be accepted, and because contracts evidently involve acceptance of the terms offered, contract can be characterised by Pufendorf as an accepted promise. Pufendorf’s train of thought in this respect may be seen from the following progression in the text of the Elementorum: first he stipulates the need for promises to be accepted,104 next discussing that promises may be conditional or unconditional,105 before finally characterising a contract as constituted by conditional promises.106 It is significant that an author who (as will be seen below) saw contract as the central obligation, nonetheless continued the existing tradition of analysing contract in promissory terms. Such a carrying over of promissory language into the analysis of contract by Pufendorf and others laid the foundations for a modern analysis of offer and acceptance which can still be classed in promissory terms and as having unilateral characteristics.107

Though in his Elementorum Pufendorf discusses promises before contract, when the chapter on Obligations is considered as a whole (and indeed when his later work is considered) it will be seen that he devotes far greater time to contract than to promise, and gives contract a much more extensive place in the scheme of obligations than did Grotius. Furthermore, having (as has been noted) characterised the duties of parties under a contract as conditional ‘promises’,108 he mixes this conceptualisation with the language of mutuality.109 A contract is a ‘perfectly mutual obligation’ arising from ‘the agreement of two or more persons … in such wise that on both sides there is an obligation of the same kind regarding one another mutually’.110 This is a strikingly modern agreement-based conception of contract. The concept of mutuality he has expounded enables him to

108See for instance the discussion in the Elementorum at I.xii.12 of what good faith requires in the performance of each party’s obligations.

109For that reason, Ibbetson’s view that ‘[f]or Pufendorf, contractual obligation derived from the duty to keep one’s promise’ (An Historical Introduction, p. 218) perhaps somewhat overstates the significance of promise in Pufendorf’s conceptualisation of contract.

110Elementorum, I.xii.12.

explain why it is that the good faith engendered by such reciprocity means that a contracting party who has not received performance is no longer bound to perform on his side (an entitlement still operative in the modern law under the name of ‘retention’ or ‘justified withholding of performance’), and also why a breach of one of the various promises made by a contracting party enables the whole contract to be dissolved111 (a concept also maintained today in somewhat modified form in the concept of fundamental or material breach).

Even though Pufendorf does not state that he is specifically turning his attention to contract until much later in his chapter,112 a significant number of his illustrations in his general treatment of obligations are in fact contractual ones, as will be seen from his treatment of error, extortion, obligations undertaken with enemies, the right of others to bind persons, illegality, formalities, pledge and suretyship. The overall impression conveyed by such attention to contract in the Elementorum is that Pufendorf saw contract as the primary vehicle by which voluntary obligations might be assumed; by contrast, the genuinely unilateral promise is given little specific treatment.

The primacy given to contract in Pufendorf’s approach to obligations is continued in his later, great work, De iure naturae et gentium. In the general chapter on obligations in this work,113 the place of contract as the principal obligation comes out even more clearly than in the Elementorum. Pufendorf begins his analysis of obligations with the idea of the agreement: agreements, he tells us, are necessary to human societies.114 He continues by explaining in the next section of the chapter (for which, building on canonical ideas, he coins the maxim ‘pacta sunt servanda’) how it is a ‘sacred precept of natural law’ that everyone must keep his word, that is to say, carry out his promises and agreements.115 In this paragraph, Pufendorf recaps the development visible in the preceding centuries from enforcement only of contracts in specific form, through canonical enforcement of bare contracts and promises backed by oath, to a rule of general civil enforcement of what is promised or contracted.

There is also in Pufendorf’s later work a refutation of the position of Connanus, Pufendorf citing Cicero at length (as well as others, including Grotius, whose similar refutation of Connanus was mentioned earlier) to demonstrate why Connanus’s view would negate gratuitous promises and thereby ‘destroy all kindness and liberality’.116 Pufendorf also devotes