theories can be categorised along various lines, and it would be impossible to do full justice to the myriad types of theory here, so only the major types of theory will be analysed.15 In any event, as noted earlier, this work is not one primarily of abstract legal theory, but seeks to consider legal theory to the extent that it assists an understanding of the role of promise within contract law in an historical context.

The theories considered below do not always provide a justification or explanation for specific rules governing promises or contracts (for instance, as to when damages will be available for breach of a promise, or when performance by a promisor may justifiably be withheld), such rules often being the result of more practical considerations, but they do purport to provide a reason why promising is considered a moral practice and one capable of creating obligations.16

(i)  Promising as a virtuous act; the natural law tradition

The first of the varieties of theory which hold that the act of promising is moral is embodied in the Aristotelian-Thomist tradition. This tradition has a long pedigree, which, following a considerable period during which it appeared to have been defeated by rationalism and utilitarianism, has undergone something of a renaissance in the past few decades.17 The tradition sees the utterance of a promise as a virtuous act, for in undertaking to benefit another at some future point we have engaged either in an act of liberality towards that other (if the promise is gratuitous) or in an act of commutative justice (if the promise is given in exchange for some

15Even then, some will quibble with the definitions and descriptions of the different types of theory described. This, however, seems inevitable in a field in which so many nuanced and overlapping theories have been offered.

16For this reason, the main thrust of Craswell’s argument, in ‘Contract Law, Default Rules and the Philosophy of Promising’, that too much time is devoted to trying to answer the philosophical question of why promises should be kept given that the various theories do not explain the choice of the specific rules of contract, seems unjustified. Theories seeking to explain why people are bound to perform certain duties cannot necessarily hope to provide definitive reasons why a particular position is adopted in relation to the consequences of breach of contract, damages, specific performance, error, and so forth. The detail of such rules will seldom be able to be deduced directly and unequivocally from the fundamental justifications offered by theories of morality for doing or not doing acts, but that does not detract from the value of such theories.

17There are a number of current proponents of various varieties of virtue ethics: see, for instance, Oakley, ‘Varieties of Virtue Ethics’. For a summary of some of the current debate in the field, see Hacker-Wright, ‘Virtue Ethics without Right Action’. For an exposition of modern contract law through the lens of virtue see, for instance, Cimino, ‘Virtue and Contract Law’; for the wider use of the concept of virtue in modern law in general, see Farrelly and Solum, Virtue Jurisprudence.

think of distributive justice as meaning an absolutely equal distribution of wealth or resources among members of society, a division perhaps to be overseen and achieved by the state. That was not the Aristotelian conception of distributive justice, however. On the contrary, Aristotle’s view of the world was a hierarchical one, in which merit (axia) was possessed in different measure by human beings. Some people demonstrate greater merit through demonstrating certain qualities (hard work, natural ability, courage, fortitude, and so forth), and so are more worthy than others. Such meritorious individuals are conceived of by Aristotle as more deserving of a greater share of wealth and resources, and so it is in keeping with the dictates of distributive justice that they should receive such greater share. Distributive justice is thus distribution proportionate to human merit. Human transactions which help to achieve such a distribution may be said to accord with the ends of distributive justice, such transactions including voluntary contracts21 and other exchanges, as well as benevolent and gratuitous transactions in favour of meritorious persons, including those founded upon promises, all of such transactions according with the end of distributive justice in so far as they assist the endowment of the meritorious with an appropriate share of wealth and resources.

Commutative justice (or, as it is alternatively translated, ‘corrective justice’22) is more evidently of relevance to voluntary transactions, of which Aristotle mentions a number of types, though it is also said to apply to involuntary transactions. Aristotle lists a number of contracts to which commutative justice clearly applies: sale, loan (with or without interest), pledge, deposit and hire.23 Commutative or corrective justice does not relate to the qualities, or merit, of the parties in a specific relationship,24 but rather relates to their interdependence (synallagma). In particular, it requires an equality in the relationship of the parties. It is in keeping with this form of justice that those who give something under an exchange should receive an equal value back for such giving. Similarly, in involuntary transactions, a party who loses out ought to be compensated for this or to receive back what he lost.

The above descriptions of the nature of both distributive and commutative justice indicate how, in Aristotelian thinking, both of these varieties

21On contracts and distributive justice, see Kronman, ‘Contract Law and Distributive Justice’; Lucy, ‘Contract as a Mechanism of Distributive Justice’.

22It is corrective justice in that it ‘supplies a corrective principle in private transactions’

Nicomachean Ethics, 1131a.

23Ibid. 24 Ibid., 1132a.

mind. In Aristotelian fashion, Aquinas provided a definition of each of these ­transactions according to the purpose, or end, which they serve.

A potential difficulty with Aquinas’s definition of commutative justice is that, as with Aristotle’s own somewhat imprecise conception, it is never clear exactly how one is to calculate in specific instances whether someone has gained too much by a transaction, and in so doing offended against commutative justice. Aquinas’s explanation is that

it is necessary to equalise thing with thing, so that the one person should pay back to the other just so much as he has become richer out of that which belonged to the other. The result of this will be equality according to the ‘arithmetical mean’ which is gauged according to equal excess in quantity.32

This presupposes that it will always be clear how one values the two sides of a transaction, but in practice that cannot always be so. In a case of an overpayment, for instance, it will be easy to conclude that the payee has received too much and to determine by how much. But how is the performance of a service to be valued? And how much, for instance, is part, defective performance of a contract worth? The Aristotelian concept of value seems to presuppose that there is an objective value which is an intrinsic quality of a service or an object, whereas neoclassical economics understands value as being subjective33 and as fluctuating according to the estimation made by human beings of something’s worth in a particular transaction (its so-called marginal utility34). The problem with the nice Aristotelian idea of an ‘arithmetical mean’ in calculating the justice of a transaction is that it gives the impression of a simple mathematic computation, which, given the subjective nature of value, will hardly ever, if at all, be the case. The point is a not unimportant one, for, if the concept of commutative justice is to be used to attack extortionate bargains for instance, then one needs to know at which point a bargain ceases to become simply a good one and becomes unjustly unbalanced in one party’s favour. The answer for Thomists lay in the conception of the ‘just price’, discussed by

32Ibid., Art. 2.

33Though some economists in various centuries have continued to promote objective ­theories of value. One such theory is the labour theory of value of objects, which argues that the value of an object is relative to the labour put into producing it: see the writings of Adam Smith, David Ricardo, and Karl Marx, among others; for a standard modern treatment of the theory, see Meek, Studies in the Labour Theory of Value.

34A concept advocated by the Austrian Economic School from the late nineteenth century onwards. The marginal utility of a good or service is that of the last unit purchased, measured by the price paid by the consumer.

Aquinas,35 a concept developed by the late scholastics (as will be seen in Chapter 3) to mean a market price. Clearly a market-based approach to assessing commutative justice is less likely to be one which interferes in parties’ contractual arrangements, in that it recognises fluctuating values, though even then it does not eradicate all difficulties in assessing transactions according to the criterion of commutative justice.36

If the market-price approach to assessing equality of exchange for the purposes of commutative justice helps to allay some fears about undue interference in contract, no such easy solution appears to apply when one has to judge human behaviour by reference to distributive justice. As Aquinas himself admits, the relevant ‘proportion’ for determining this will differ depending upon whether the government of a society is aristocratic, oligarchic, democratic, or one of the other various forms of government regulated according to ‘various forms of community’.37 The difficulties for using the concept of distributive justice in any way likely to produce self-evidently correct answers in contractual disputes must be obvious, and should be a warning against attempting to use this form of justice as a basis for regulating specific contracts. Indeed, as Fried once remarked,

liberal political theory (and practice) accept distributive justice as a goal of collective action, but one to be pursued by the collectivity as a whole, funded by the general contribution of all citizens.38

Fried, in consequence, took the view that individual contracts should not be subject to redistributive action on the basis that they were unconscionable, because ‘it is unfair (and in the end unrepresentative) to force particular persons, who are making their private arrangements against the background of conditions they did not create, to bear the burden of remedying these conditions’.39

Aquinas discusses promises principally in the context of vows,40 and of marriage (including betrothal) in particular.41 As discussed in Chapter 1, a vow is a special type of promise, a ‘promise made to God’ as Aquinas ­succinctly puts it.42 A promise is a voluntary act43 by which one undertakes

35Summa Theologica, II-II, Q. 77, Art. 1.

36For instance, what of the seller who has good reason for selling below the market price, as a favour to the buyer or because he requires to sell his stock quickly? Is such a contract not in conformity with commutative justice because of the lower-than-market price?

41Ibid., Supplement, Q. 43 (betrothal), Q. 46 (promise of marriage).

42Ibid., II-II, Q. 88, Art. 2.

43‘Something that one does voluntarily for another’ (ibid., II-II, Q. 88, Art. 2).

to benefit another,44 ‘since it would not be a promise but a threat to say that one would do something against someone’.45 Aristotle had located promising within the virtues of liberality or justice, depending on the reason for their being made, but Thomas adds that the virtues of honesty46 and fidelity require the fulfilment of promises, as does the natural law.47 This fusing of Aristotelian teleology and the concept of the virtues with a Thomistic theory of natural law was part of the genius of Aquinas’s use of the Greek philosopher’s ideas.

Though the kernel of the idea of natural law can be located in an Aristotelian discussion of natural justice in Book V of the Nicomachean Ethics, it was Aquinas who developed this into a fully worked out theory which taught that certain immutable laws are inherent in the (divinely ordered) natural world, and that these laws may be discovered through man’s divinely given reason.48 The significance of this for present purposes is that the duty to adhere to promises made and contracts entered into (as well as to vows) is conceived of in the Thomist worldview as one of the duties deriving from the natural law, though Aquinas recognises that, while the natural law might enjoin adherence to all promises, it was entirely proper that the civil law might require certain formalities of promising before a promise could be held to give rise to legal rights.49

The natural law/virtue conception of promise does not necessarily exalt the moral requirement to keep a promise above all other natural laws, such that no circumstances could ever permit the breach of a promise once made (a telling point against those like Fox and Demarco who argue that promising must be immoral given its non-receptivity to other moral norms)50. While, in general, says Aquinas, a failure to adhere to a promise shows a lack of fidelity to the promisee, there may be a reason excusing such a failure.51 First, where a promise is made to do something unlawful,

44‘We promise something to a man for his own profit’ (ibid., II-II, Q. 88, Art. 4). By contrast, continues Aquinas, a vow is a promise made to God for our profit, not for God’s profit, which poses some difficulties for the definition of a promise adopted in this work, namely a commitment made to benefit another.

45Ibid., II-II, Q. 88, Art. 2.

46For Aquinas, it is a lie if one does not do what one has promised: ‘mendacium est, si quis non impleat, quod promisit’ (ibid., II-II, Q. 110, Arts. 3, 5).

47Ibid., II-II, Q. 88, Art. 3.

48Aquinas discusses the nature of law, including natural law (ibid., II-I, QQ. 90–7). For a treatment of the history of natural law theory see McCoubrey, The Development of Naturalist Legal Theory.

49‘But for a man to be under a civil obligation through a promise he has made, other conditions are requisite’ (Summa Theologica, II-II, Q. 88, Art. 3).

50See the earlier discussion of Fox and Demarco, at p. 66.

51Summa Theologica, II-II, Q. 110, Art. 3.

the promisor is excused, it being better that the unlawful act is not committed. Second, if the circumstances have changed, such that performance of the promise cannot be achieved, this may also act as an excuse.52 Admittedly, this second excuse seems somewhat wide in its potential ambit, especially as expressed in the words of Aquinas (‘if circumstances have changed with regard to persons and the business in hand’), but we may reasonably assume that Aquinas did not have in mind every conceivable change which might occur since the making of the promise, but rather more restricted types of change (such as what might in the modern law be called frustrating circumstances beyond the control of the parties).

The natural law conception of fundamental moral duties, such as that created by a promise, is not unique to Thomistic writing, or even to the wider Christian tradition, for one can conceive of there being a natural law without belief in a Christian deity, or even in any deity at all, but rather because of a belief that nature and human beings just happen to be the way they are, and that part of such human nature is that we are predisposed to make and to adhere to promises. The attraction of the natural law approach, especially when posited on a theistic basis, is in providing an objective foundation for the moral force of promises, one which, because of human nature, is permanent, non-fluctuating, and not therefore subject to human whim or alteration. In the Western legal tradition, however, the close association of natural law theory and Christian theology subjected such theory to increasing criticism in a post-Enlightenment, sceptical, increasingly humanist society. However, by this stage, as will be seen in the following chapter, natural law ideas had become welded to the concept of the force of promise as lying in the human will, a concept which was entirely in keeping with the approach of Enlightenment philosophy and thus able to be utilised as a continuing basis for respecting promises even as the popularity of natural law ideas waned.

Thus far, the discussion has shown how the Aristotelian/Thomist tradition explained promising to be moral because it was a vehicle giving effect to those virtues which contributed to the ultimate end of man. In addition, the tradition held the view that the moral nature of promises

52Aquinas cites here in support a passage from the writing of Seneca (De Beneficiis IV) as well as the changed circumstances related in 2 Cor. 1 which prevented the Apostle Paul from honouring a promise to go to Corinth. Similarly, someone may be released from a vow or an oath if the circumstances have changed: Summa Theologica, II-II, Q. 88, Art. 10; II-II, Q. 89, Art. 9.