In my Roman law and jurisprudence classes, my students and I spend some time puzzling over how to classify 'innominate contracts.' Classical Roman lawyers were allergic to abstract reasoning over legal concepts. They had no interest in crafting a 'general theory' of contract, in the way legal philosophers now try to. They only cared about specific contracts for specific types of legal transactions that evidently were most common in Roman society and economy - thus, Sale (emptio-venditio), Partnership (societas), Stipulation (verbal agreement) - and the specific remedies attached to them (actio empti; actio venditi; actio pro socio; condictio; etc.). This article by Alan Watson is an excellent overview of the subject.
These contracts, with specific names and specific remedies, were generally called the 'nominate contracts.' They were so named to distinguish from all other informal contract-like arrangements and transactions that did not fit into any of the legally recognized nominate contracts. Such unnamed, formless agreements were called the 'innominate contracts' and, at least originally, were 'unclothed' (nuda) - that is, were unenforceable (although later they become enforceable under what were called actions 'praescripta verba').
Barter-exchange (permutatio) was a classic example. Recognized as the ancestor of the contract of sale (at D.18.1.1), barter was seen to be a species of contract involving what lawyers simply called 'do-ut-des' (= 'I give you something, just as you give me something'). But unlike sale, where money and an agreed-upon price is essential, there is no monetary aspect to barters - and for this reason, they were regarded as unenforceable by courts. Whatever obligation arose from a barter, therefore, was not a legal obligation - at most, it was a natural obligation.
Gaius and Justinian famously attempted classifications of contracts in their various 'divisiones obligationum.' Students still learn these (the real, verbal, literal, consensual contracts). But these were not intended to be theoretical - they never give us anything like a general or universal theory of contract. And yet, they provide the raw materials for such a general theory, partly in the problem of classifying innominate contracts (the same could be said for pacts, promises, and the so-called 'quasi-contracts' - perhaps for another post).
Ok - all of this background has led me to a section in Grotius that has left me bewildered for years, and I have not found satisfactory literature explaining the significance of it. I have now spent some time on it, and looking at the older commentaries from the Enlightenment. It concerns these opening passages (De Jure Belli ac Pacis II, 12):
There are several points worth noting, in these opening passages. The first is the very fact that Grotius is attempting what his classical ancestors avoided - a typology of contracts. The typology, however, is unlike anything in the classical Roman law sources. Grotius's starting point is 'acta' - all contracts are acts, of various kinds. And this, I suspect, is to distinguish from the analysis of promises (the subject of the previous chapter) which ultimately reduces to the will (animus; voluntas). By focusing on externally observable actions, Grotius seems to be pushing his analysis of contracts towards legal 'consideration' - something of value must actually be rendered to another in order for there to be a contract.
And this is how he defines contract: 'All acts useful to others, beyond simple kindnesses.' The marginal reference is to a famous text in D.50.16.19 which declares that all contracts must be 'synallagmatic' - that is, some mutual exchange of considerations must take place. But Grotius is very flexible on what could count as considerations. Such 'useful acts' could be money, property, services.
That casts a very wide net, and it includes a whole range of 'useful acts to others' that could be described as contractual. These include the so-called real contracts: commodatum, mandatum, depositum, all of which are described as acts involving 'something approximating a mutual obligation' (mutua quadam obligatione). Even though these are technically gratuitous (e.g., one does not pay a depositary to leave property in deposit), there is still a kind of exchange involved (e.g., because the depositary holds the property in trust and must return it in the future).
This is all the more manifest in those acts described by Grotius as 'permutarii acta.' And it is under this label that he brings together both the innominate and nominate contracts. Grotius II, 12, §3: Grotius's discussion of the difference between innominate and nominate contracts illustrates his familiarity with the classical treatment: Some contractual forms (like Sale, Partnership, Stipulation) were used more frequently, the praetors recognized and privileged their usage with special legal remedies. But even the innominate contracts received some remedy through a formula known as the 'praescriptis verbis' action.
But it is what he says after this that is most striking:
'But the law of nature ignores these distinctions (= distinctions between nominate and innominate contracts): These contracts which are called 'innominate' are neither less natural, nor less ancient. On the contrary, barter (permutatio) which is considered to be an innominate contract, is much simpler and more ancient than the contract of Sale,' before the invention of money (the point being, that commerce precedes money; sociality precedes commerce).
This is a good example, in my view, of how law of nature reasoning went hand-in-hand with the early modern effort to develop a general theory of contract. Grotius was, by no means, the most important figure in this effort. In fact, the real innovators were theologians - figures like Lessius, Molina, de Soto. One of the best books on this subject is this one.
One last point I want to make. This was not the only place where Grotius dealt with the problem of classifying innominate contracts. It also appears in his system of Roman-Dutch law, the Hollandsche Rechtsgeleerdheid.
Grotius's purpose in this work is, of course, different. He is outlining a relatively novel system of law for Holland, not natural law. So the set up will be different from both Roman law and natural law. But the differences are important.
III, 1, §9: There are two natural sources of rights and obligations - contracts and inequality. Here, Grotius regards contracts broadly (similar to the wide-net cast, in the analysis earlier), and so relates them to 'promissio' but specifically distinguishes them from bare promises (beloft; polliciatio). Inequality, by contrast, is the obligation arising from situations where one profits at the expense of another. The most important case involves unjust enrichment (corresponding to the Roman quasi-contract of indebitum).
Where do innominate contracts fall within this Roman-Dutch scheme?
Under inequality: Innominate contracts aren't really contracts at all. He treats them here more as cases of favor- and gift-exchanges designed to strengthen ties of sociality. I do a favor for you; you are indebted to return the favor to me. You give me a really nice gift; I am indebted to return the favor.
Earlier, Grotius was able to explain this under a theory of considerations (all that stuff about 'acta'). But here, he seems to have changed the story. What I can't tell now is whether this was an intentional shift; if there was something specific about Roman-Dutch law that led him to this differentiated treatment of innominate contracts. But it simply reinforces the intellectual challenges that civilian lawyers faced in articulating a general theory of contract and contractual duties, based on a system that resisted such generalization.
I suppose another way of approaching this issue is to ask what is NOT a contract. An eminently reasonable answer would be to say something like a gift (donatio). But strangely, gift - or at least certain legal categories of gift - were considered contractual in nature because gifts could technically be 'extra mere beneficos.'
