summa divisio in duo genera diducitur: namque aut civiles sunt aut praetoriae. civiles sunt, quae aut legibus constitutae aut certe iure civili comprobatae sunt. praetoriae sunt, quas praetor ex sua iurisdictione constituit, quae etiam honorariae 2 vocantur. Sequens divisio in quattuor species diducitur: aut enim ex contractu sunt aut quasi ex contractu aut ex maleficio aut quasi ex maleficio. prius est, ut de his quae ex contractu sunt dispiciamus. harum aeque quattuor species

rariae obviously does not correspond with that explained in Excursus V inf. into civil and natural: it has reference, as appears from the text, to the legislative organ by which it was declared that such or such an act or event should engender a (civil) obligation. In this sense civiles obligationes are those which were made actionable by the organs of the civil law-by a lex, plebiscitum, senatusconsult, imperial constitution, or by the action of the jurists: obligationes praetoriae are those which owed their actionability to the edict: 'quas praetor ex sua iurisdictione constituit' seems to mean 'quas, occasione a iuris dicundi munere sumpta, decretis primum, deinde edicto perpetuo constituit.'

§ 2. The sources of obligations are thus enumerated by Modestinus in Dig. 44. 7. 52 res-verba-consensus (the three forms of contractual liability)—lex-ius honorarium-necessitas-peccatum. Lex and necessitas he explains as follows: 'lege obligamur, cum obtemperantes legibus aliquid secundum praeceptum legis aut contra facimus: . . . necessitate obligantur quibus non licet aliud facere, quam quod praeceptum est : quod evenit in necessario herede.' The fourfold division of Justinian, though more complete than that given by Gaius in his Institutes (iii. 88), is in effect derived from the same writer's liber tertius aureorum (Dig. 44. 7. 5.), from which Justinian literally takes his instances of quasicontract and quasi-delict, and in which (§§ 1 and 5) these terms occur, though a few lines above they are comprised under the perplexing expression variarum causarum figurae.' The meaning of these four sources of obligations will appear sufficiently from the text relating to them respectively: but they do not comprehend all the obligations of Roman law, and therefore the classification must be condemned as in the first place inexhaustive. Contracts (sensu Romano) are those agreements which were actionable under even the old civil law: but in course of time a considerable number of other agreements were made actionable by the influence of the jurists, the edict, and imperial enactment: in none of these, which the commentators call pacta vestita, to distinguish them from pacta nuda, was the obligation said to arise ex contractu, and in fact they have no place whatever in Justinian's arrangement. system of law probably can dispense with the notion of quasi-contract, for there must always be circumstances in which one person is placed under an obligation to another without any promise, express or implied, made by him to the latter, and which yet so closely resemble those of

No

sunt: aut enim re contrahuntur aut verbis aut litteris aut consensu. de quibus singulis dispiciamus.

contract as to make quasi-contract their most reasonable denomination : but the fault of Justinian is that nothing which he says about quasicontract suggests any general criterion by which one can precisely draw the line between it and contract proper, or which accounts for the existence of an obligation in the particular instances by which he illustrates the conception. But the idea of quasi-delict, which is open to the same objection, is further to be condemned as really unnecessary, as will appear from the cases by which it is exemplified (Bk. iv. 5 inf.), most of which are instances of vicarious responsibility analogous to the liability in tort of a railway company or other employer for the wrong-doing or negligence of its servants. Its existence is to be accounted for purely on historical grounds (see Hunter's Roman Law p. xxxvi), and it is to be regretted that Justinian tolerated its survival. The actual sources of obligation in Roman law may more logically be arranged as follows: (1) Agreement, comprising the four classes of contracts, the so-called innominate contracts, and pacta vestita. (2) Quasi-contract, including tutela, cura, negotiorum gestio, joint inheritance, joint ownership not arising ex contractu, litis contestatio, and perhaps the unjust enrichment of one man at the cost of another (cf. Tit. 14. 1 with Tit. 27. 6 inf.). (3) A person's mere 'unilateral' expression of will (exemplified by some cases of pollicitatio, e. g. Dig. 50. 12. 1. 1, ib. 2, though as a general rule 'ex nuda pollicitatione nulla actio nascitur' Paul. sent. rec. 5. 12. 9), or that of another by whose decease one has taken a benefit (exemplified by legacy and fideicommissum). (4) Judgment or magisterial order. (5) Delict. For an enumeration of the sources of obligation in English law see Sir W. R. Anson's Law of Contract (Introductory chapter).

The idea of agreement (conventio or pactio) underlies that of contractus: 'et est pactio duorum pluriumve in idem placitum consensus' Dig. 2. 14. 1. 2. Its analysis into the elements of offer or proposal and acceptance is the work rather of general jurisprudence than of a particular system, which has been done once for all by Savigny, Oblig. § 52, System iii. §§ 140, 141: cf. Pollock's Principles of Contract, chap. i. Pactio then is the genus of which contractus is the species: the differentia lies in the circumstance that to certain pacta or pactiones a civilis obligatio was annexed by the older Roman civil law in virtue either of their nature, or of their being attended by some other fact besides the mere fact of agreement. That, through which a pactum is also a contract, is usually called its causa civilis, and of such causae civiles there are four, viz. (1) res, delivery of ownership, possession or detention of an object by the creditor, whence the four Real Contracts. (2) The expression of the agreement in a certain verbal form (obligatio verborum), that of question and answer (stipulatio) being regarded as the verbal contract par excellence. (3) The employment of writing in a manner peculiarly characteristic of the Romans, whence the obligatio

XIV.

QUIBUS MODIS RE CONTRAHITUR OBLIGATIO.

Re contrahitur obligatio veluti mutui datione. mutui autem obligatio in his rebus consistit, quae pondere numero mensurave constant, veluti vino oleo frumento pecunia numerata aere argento auro, quas res aut numerando aut metiendo aut pendendo in hoc damus, ut accipientium fiant et quandoque nobis non eaedem res, sed aliae eiusdem naturae et qualitatis reddantur. unde etiam mutuum appellatum sit, quia ita a me tibi datur, ut ex meo tuum fiat. ex eo contractu nascitur

litterarum; and (4) in transactions of four specific kinds the mere agreement (consensus) of the parties: whence the consensual contracts of sale, hire, partnership, and agency. How other parts besides these were gradually made actionable, though not dignified by the Romans with the name of contract (which is less a legal than a historical term) will appear as we proceed.

It is difficult to say why Gaius (whom Justinian follows) discussed the four classes of contracts in the order-Real, Verbal, Literal, and Consensual. Mr. Poste supposes that it was perhaps the order of their chronological development, here following Savigny, who holds that mutuum was the earliest contract which the Roman law enforced by action for an acute criticism of this hypothesis, and of Ortolan's and Sir Henry Maine's theory that there was a time when the Roman law possessed but one common form for contract and conveyance (the negotium per aes et libram), see Hunter's Roman Law pp. 352-379, where the whole question of the origin and development of the Roman contract system is well and fully discussed.

The real and consensual contracts were said to be iuris gentium and to suppose that one of these (mutuum), at any rate in the form in which we know it, was actionable at Rome before the formal civil law contract of stipulatio seems entirely opposed to the general conclusions of historical law. On the other hand it must be admitted that mutuum seems to stand clearly apart from the three other real contracts: the remedy on it was condictio, a stricti iuris iudicium, while they were all pursued by bonae fidei actions; and in mutuum the borrower is made owner of the thing borrowed; the lender 'dat,' i. e. parts with his own dominium whereas in the other three nothing is ever transferred beyond possession, so that the transferor can always in case of breach recover his own by real action. These in fact seem to have been derived from fiducia (the nature of which has been already described, p. 315 supr.), and the action on which was bonae fidei, Gaius iv. 62: the difficulty of ascribing the same origin to mutuum lies in the difference of the remedy.

:

Tit. XIV. The obligation in a real contract is generated by delivery,

actio quae vocatur condictio. Is quoque, qui non debitum 1 accepit ab eo qui per errorem solvit, re obligatur: daturque agenti contra eum propter repetitionem condicticia actio. nam proinde ei condici potest 'si paret eum dare oportere ac si mutuum accepisset: unde pupillus, si ei sine tutoris auctoritate non debitum per errorem datum est, non tenetur indebiti condictione non magis quam mutui datione. sed haec species obligationis non videtur ex contractu consistere, cum is qui solvendi animo dat magis distrahere voluit nego

whether what passes is dominium, as in mutuum, possession, as in pignus, or detention, as in commodatum and depositum. The bare agreement to deliver was by itself not binding: else the contract would have been not real, but consensual.

A mutuum (loan for consumption, as contrasted with commodatum, loan for use) exists only if the property passes in what is lent: 'si non fiat tuum, non nascitur obligatio' Dig. 12. 1. 2. 2, so that as a general rule no one can lend in this form unless he is owner, Dig. ib. 2. 4, and has the capacity of alienation, Bk. ii. 8. 2 supr.: cf. Dig. 26. 8. 9. pr. The chief duty of the borrower is specified in the text, viz. to give back as much and as good as was lent him: not the same thing, for only those objects can be thus lent which the commentators call res fungibiles, and the Romans quantitas; or, as it is otherwise expressed, they have to be returned not in specie, but in genere. Unless a date for repayment was agreed upon either expressly or by implication, it could be demanded at any time. If interest was part of the bargain, it could not be sued for under the mutuum itself, owing to the nature of the remedy: the agreement to pay it must be entered into by stipulation, so that it, and the promise to repay the principal, were distinct contracts. The action on a loan of money was called condictio certi, that on any other mutuum condictio triticaria: see the references in the General Index. For the bearing of the SC. Macedonianum on the law of money loans see Bk. iv. 7. 7 and notes inf.

§ 1. In Tit. 27. 6 inf. (derived from Gaius in Dig. 44. 7. 5. 3) the person to whom money not really due is paid by mistake is said to be bound to return it quasi ex contractu. In Gaius' time (iii. 91) it had been a moot point whether a pupillus to whom such a payment had been made without his guardian's auctoritas was liable to condictio indebiti; perhaps this was part of the larger question whether a pupillus was bound even naturaliter by his unauthorized contracts, Dig. 26. 8. 5, pr. and 1. Gaius himself was in favour of the affirmative opinion, which on principle seems right, for (as Mr. Poste says) condictio was not founded on contract, but on the fact that a defendant had been without cause enriched at the expense of the plaintiff.

Condictio indebiti lay only under the following conditions:

(1) What is paid must not really be owed by the one party to the

2 tium quam contrahere. Item is cui res aliqua utenda datur, id est commodatur, re obligatur et tenetur commodati actione. sed is ab eo qui mutuum accepit longe distat: namque non ita res datur, ut eius fiat, et ob id de ea re ipsa restituenda tenetur. et is quidem qui mutuum accepit, si quolibet fortuito casu quod accepit amiserit, veluti incendio ruina naufragio aut latronum hostiumve incursu, nihilo minus obligatus permanet. at is qui utendum accepit sane quidem exactam diligentiam custodiendae rei praestare iubetur nec sufficit ei tantam diligentiam adhibuisse, quantam suis rebus adhibere solitus est, si modo alius diligentior poterit eam rem custodire: sed propter maiorem vim maioresve casus non tenetur, si modo non huius culpa is casus intervenerit: alioquin si id quod tibi commodatum est peregre ferre tecum malueris et vel incursu hostium praedonumve vel naufragio amiseris,

other, even naturaliter: 'si quod dominus servo debuit manumisso solvit, quamvis existimans ei aliqua teneri actione, tamen repetere non poterit, quia naturale agnovit debitum' Dig. 12. 6. 64, 'indebitum est non tantum, quod omnino non debetur, sed et quod alii debetur, si alii solvatur, aut si id, quod alius debebat, alius, quasi ipse debeat, solvat' Dig. ib. 65. If the defendant in an action in which 'lis crescit in duplum' (Tit. 27. 7 inf.) admitted his liability and paid the single damages, and subsequently was able to show that in fact he had not been liable, he could not recover the money as indebitum (loc. cit., Gaius ii. 283), on the ground that his voluntary payment was in effect a compromise, and so by implication a contract. On this principle money paid under a supposed but non-existent judgment was irrecoverable, Dig. 10. 2. 36: conversely, if, though there is an actual debt, the debtor pays something different from what he really owes, he can recover, Dig. 12. 6. 32. 3.

(2) The payment must be made in error: 'et quidem si indebitum ignorans solvit, per hanc actionem condicere potest: sed si sciens se non debere solvit, cessat repetitio' Dig. 12. 6. 1. 1: and this in some cases even if the mistake was one of law, Dig. 36. 4. I pr.; 12. 6. 32. 2.

(3) The payment must be accepted by the payee in good faith; i.e. he must believe the debt to be due: else he commits theft, and should be sued by condictio furtiva, which excludes the condictio indebiti: Dig. 47. 2. 43; 13. I. 18.

The defendant in condictio indebiti, if judgment went against him, was not bound to restore the whole of what had been paid him, but only so far as he was enriched by the payment at the time of litis contestatio : 'bonae fidei possessor in quantum locupletior factus est tenetur' Dig. 12. 6. 3; ib. 26. 12; ib. 32. pr.

§ 2. The duties of the borrower in a commodatum besides that of rea