Учебный год 22-23 / The Law of Obligations

classical lawyers "unflinchingly observed";131 and although we have already seen that the rule was not quite as "iron" as Schulz leads us to believe,132 it is certainly true that <L general right of rescission in case of breach of contract was never recognized in Roman law.133 Despite several attempts to reverse the principle (especially by the canon

131Schulz, CRL, p. 532.

132Supra, p. 578.

133However, if one of the parties to a reciprocal contract did not perform, the other party could refuse to counterperform ("functional synallagma": cf. Benohr, Synallagma, p. 1). Such mutual interdependence of the two obligations had to be brought about, originally, by way of a special clause appended to the contract (cf. e.g. Lab. D. 18, 1, 78, 2 (". . . ea lege emerat, ut soluta pecunia traderetur ei possessio"); cf. further Benohr, Synallagma, pp. 20 sqq.); in classical law, however, the judge was taken to be empowered, by virtue of the "ex bona fide" clause contained in the formulae of the actiones empti, vendiditi, locati and conducti, to take account of the fact whether the plaintiff had himself performed his obligation. If he had not done so up to the time when judgment was given, the defendant had to be absolved. In other words: the exceptio non adimpleti contractus {as this right of the defendant to retain his own performance came to be called from about the 15th century onwards) was inherent in the Roman bonae fidei iudicia. Cf. Ulp. D. 19, 1, 13, 8; Scaev.

D. 18, 4, 22; Marcell./Ulp. D. 21, 1, 31, 8; Benohr, Synallagma, pp. 27 sq.; Alfons Burge,

Retentio im romischen Sachenund Obligationenrecht (1979), pp. 186 sqq. The same applied in cases of contractus bilaterales inaequales, if the plaintiff brought the actio directa without having discharged his obligations arising under the actio contraria; cf. Pomp. D. 13, 7, 8 pr. and 1; Paul. D. 47, 2, 15, 2; Iul. D. 47, 2, 60 and, for a detailed analysis, Burge, Retentionsrechl, pp. 163 sqq. The idea underlying the Roman sources was generalized by the commentators ("Ex contracto ultro citroque obligatorio non potest effectualiter agi nisi ab eo qui totum contractum ex parte sua impleverit": Bartolus, Commentaria, ad D. 19, 1, 13, 8; apart from the individual instances of Roman law, this rule was often based on the general principle of fidem frangenti fides frangitur of the medieval canon law; on which see, in the present context, Friedrich Merzbacher, "Die Regel 'Fidem frangenti fides frangitur' und ihre Anwendung", (1982) 68 ZSS (KA) 347 sqq.) and the "exceptio non adimpleti contractus" remained part and parcel of the ius commune down to the days of the pandectists (cf. e.g. Gluck, vol. 17, pp. 225 sqq.; Windscheid/Kipp, § 321, 1; for a historical analysis, see Schemer, Riicktrittsrecht, pp. 53 sqq.; cf. also Jansen JA in BK Tooling (Edms.) Bpk. v. Scope Precision Engineering (Edms.) Bpk. 1979 (1) SA 391 (A) 416 sqq.) and was incorporated into the BGB ("Whoever is bound by a mutual contract may refuse to perform his part until the other party has performed his part, unless the former party is bound to perform his part first" (§ 320 11 BGB; cf. also § 271 I 5 PrALR)). No provision corresponding to § 320 BGB exists in the French code civil, but courts and legal writers have applied the law as if it did (for details, see Nicholas, FLC, pp. 207 sqq.; cf. also Jansen JA in the BK Tooling case at p. 417A-D). The application of the exceptio non adimpleti contractus in modern South African law has led to considerable difficulties and confusion in cases where the plaintiff has been guilty of malperformance. May the defendant refuse to render counterperformance even though he is in possession of, and possibly even uses, the plaintiff's defective performance? In a famous trilogy of cases {Hauman v. Nortje 1914 AD 293; Breslin v. Hichens 1914 AD 312; Van Rensburg v. Straughan 1914 AD 317) it was established that the absolute nature of the exceptio non adimpleti contractus indeed precluded any contractual claim by the malperforming plaintiff; yet, in order to avoid inequitable results, an enrichment action for "quantum meruit" was granted (calculated by deducting the cost of remedying the defective performance from the contract price). This approach (based, probably, on a misunderstanding—De Vos, Verrykingsaanspreeklikheid, pp. 275 sqq.; De Wet en Yeats, pp. 181 —of Voet, Commentarius ad Pandectas, Lib. XIX, Tit. II, XL) has been subjected to severe criticism (cf. De Vos and De Wet en Yeats, loc. cit.; J.C. de Wet, "Die sogenaamde

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lawyers and, later, by the adherents of the school of natural law),134 it was retained—at least as far as the theory of the Roman ius commune was concerned—down to the days of the pandectists.135 It had taken a long time to establish the principle that even formless, merely consensual pacta are binding, and there appears to have been a natural reluctance to jeopardize the grand new idea of pacta sum servanda by recognizing a general unilateral right of withdrawal from contract.136 In the case of mora a narrowly circumscribed exception had come to be recognized in 19th-century legal science,137 but the fundamental break with traditional doctrine was effected only by the fathers of the BGB.138 Conceptually, it was the lex commissoria that stood at the cradle of this development.139 Thus we find Windscheid arguing that the right of withdrawal in case of mora debitoris could, under certain circumstances, be taken to have been (tacitly) agreed upon;140 and even the BGB still refers to its provisions dealing with rights of rescission ex contractu141 when it deals with statutory rights of rescission in case of non-performance.142 Furthermore, since a lex commissoria had a resolutive effect, rescission of the contract was seen to remove the basis for a claim for damages. This explains the strict alternativity between

damages for non-performance and rescission according to §§ 325 sq. BGB.143

'exceptio non adimpleti contractus' in die praktyk van vandag", (1945) 9 THRHR 239 sqq.); in the BK Tooling case (1979 (1) SA 391 (A)) the Appellate Division ultimately took the opportunity to re-examine the matter. Use of the plaintiff's defective performance, it was now argued by Jansen JA, creates a discretion for the court to determine whether the defendant may raise the exceptio (and thus bar the plaintiff's claim for remuneration). In cases where the exceptio may not be raised, the plaintiff may bring his contractual action, albeit only for a reduced remuneration. For details, see Christie, Contract, pp. 419 sqq.; Joubert, Contract, pp. 232 sqq.; Zimmermann, RHR, pp. 116 sq.; cf. now also Thomas

Construction (Ply.) Ltd. v. Grafton Furniture Manufacturers (Pty.) Ltd. 1986 (4) SA 510 (N); for the solution in German law of cases of this nature, cf. Emmerich, op. cit., note 83, § 320, nn. 11, 37 sqq.

134Cf. supra, p. 579.

135Cf. e.g. Windscheid/Kipp, § 321, 2.

136Leser, Rucktritt vom Vertrag, p. 4.

137Cf. Windscheid/Kipp, § 280, n. 1; on the developments in 19thcentury commercial law, see Karl Schemer, Rucktrittsrecht, pp. 157 sqq.

138For a detailed discussion, see Lcser, Rucktritt vom Vertrag, pp. 26 sqq.

139Leser, Rucktritt vom Vertrag, pp. 16 sqq,

140Windscheid/Kipp, § 280, n. 1.

141§§ 346 sqq. For a concise overview of the remedy of rescission in German law (under which circumstances is it available?; what are its characteristic features?), see Brice Dickson,

"The Law of Restitution in the Federal Republic of Germany: A Comparison with English Law", (1987) 36 International and Comparative Law Quarterly 762 sqq.

142§ 327.

143"Motive", in: Mugdan, vol. II, p. 116. The position is different in, for instance, French (art. 1184 II code civil), English and South African law. The alternativity of remedies in the BGB has often been criticized; cf. e.g. Leser, Rucktritt vom Vertrag, pp. 138 sqq.; Huber, op. cit., note 5, pp. 713 sqq., 763.

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2. The notion of an implied condition (natural law)

The natural lawyers adopted a slightly different point of departure. They argued that the obligations of the two parties to a mutual contract were dependent, in the sense of being conditional, upon each other. If one of them did not perform, the other did not have to make performance either and he thus gained the right to abstain from the contract:

"|n]am unius ejusdemque contractus capita singula alia aliis inesse videntur per

modum conditionis, quasi exprcssum csset, haec ita faciam si et alter faciat quae promisit."1 "

This idea found its most mature expression in art. 1184 code civil: a resolutive condition is always implied in synallagmatic contracts to provide for the case where one of the parties does not fulfil his undertaking. However, the contract is not resolved by operation of law in this case, but at the choice of the party with regard to whom the undertaking has not been performed. This provision, inspired by Domat and Pothier,145 tied in nicely with the practice which the French courts had been following anyway;146 already since the days of Molinaeus one had felt to be both entitled and compelled "de se deporter, dans les tribunaux, de la rigeur de ces principes" (that is, the Roman rejection of a general right of rescission).147

3. Condition and warranty in English law

The idea of a condition as basis andjustification for a right of rescission has not been confined to continental jurisprudence; in England it has been described as the "key to the modern theory of breach of contract".148 We have seen that traditionally the claim for damages for breach of contract is the central contractual remedy according to the English common law.14y Every contractual term, express or implied, is in law a "warranty", and breach of a warranty entitles the innocent party to claim damages. If, however, the term which has been broken is not only a warranty but also a "condition", the innocent party has the option of withdrawing from the contract: he can refuse to render performance or reclaim whatever has already been transferred.150

144 Grotius, De jure belli ac pads. Lib. Ill, Cap. XIX, 14; cf. further Schemer,

Rucktrittsrecht, pp. 92 sqq.

145Georges Boyer, Recherches hisloriques sur la resolution des contrats (1924), pp. 381 sqq.

146For details, see Boyer, op. cit., note 145, pp. 32У sqq., 343 sqq., 350 sqq. Cf. also

Coing, pp. 443 sq.

147Pothier, Traite dti contrat de vente, n. 476.

148Samuel J. Stoljar, "The Contractual Concept of Condition", (1953) 69 LQR 485.

149Cf. supra, pp. 776 sqq.

On the development and specific meaning of the notion of a condition in this context,

see Rhcinstein, Stmhtur, pp. 192 sqq. As on the Continent, rescission was a relatively late addition to the remedial processes available to the aggrieved party. It became established only in the late 18th century. Of cardinal importance were two decisions of Lord Mansfield in Kingston v. Preston, reported sub Jones v. Barkley (1781) 2 Dougl 684 at 690 sq., and Boone v. Eyre (1779) 1 H Bl 273.

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The term "condition" has been defined as

"|a] stipulation [which] goes to the root of the matter, so that a failure to perform it would render the performance of the rest of the contract . . . a thing different in substance from what |had been] stipulated for";l sl

failure of performance must have "substantially" deprived the other party of what he had bargained for. Today the formal categories of warranty and condition have largely been abandoned in favour of the distinction between the essential and non-essential terms of a contract.152 This means, in the case of mora debitoris, that the creditor may, of course, claim damages in any event; in addition, he is entitled to rescind the contract, if the time within which performance must be made is "essential" to the contract. The right of rescission thus requires, in the phraseology of English law, that "time is of the essence of the contract".153 Whether the parties intended time to be of the essence, is determined by the judge according to the individual circumstances of each case; the fact that a specific time for performance has been expressly fixed in the contract is no longer154 regarded as conclusive.155 If time does not appear to be "of the essence", the creditor is still able to elevate it to that status by giving the debtor a notice of rescission and allowing him a further reasonable time for performance.

4.Condition, lex commissoria and rescission in South African law

Both the notion of "time is of the essence" and that of the notice of rescission have, incidentally, percolated into South African law. Despite an old Dutch custom in favour of a right of rescission in case of delay of performance,156 the Roman-Dutch writers (unlike their French counterparts) stuck to the principle of Roman law. Thus, for instance, as far as the law of sale is concerned, Voet states quite unambiguously that

". . . ob pretium поп solutum non recte venditor contendit ad emptionis dissolutionem, reiquc jam per traditionem translatae restitutionem; sed magis ad

151Bettini v. Gye (1876) 1 QB 183 at 188.

152Cf. e.g. Hongkong Fir Shipping Co. Ltd. v. Kawasaki Kisen Kaisha Ltd. [1962] 2 QB 26

("There are . . . many contractual undertakings of a more complex character which cannot be categorized as being 'conditions' or 'warranties' ": p. 70, per Diplock LJ); Treitel, Contract, pp. 585 sqq.; Zwcigert/Kotz, pp. 223 sqq.

153For details cf. e.g. Treitel, Contract, pp. 631 sqq.

154Since s. 27(7) of the Judicature Act (1873), which caused [he rules developed by Equity

to prevail over those applicable "at law".

^5 According to United Scientific Holdings Ltd. v. Burnley Borough Council [1977] 2 WLR 806 (HL) at 826F, time, in modern English law, is prima facie not of the essence of the contract.

156Heinrich Mitteis, Rechtsfolgen des Leistungsverzugs beim Kaufvertrag nach niederidndischen

Quellen des Mittelalters (19)3), pp. 176 sqq.

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implementum ejus cxperiendum est. . . .; nisi ab initio id nominatim convenerit, ut ab emptione ob moram in ca implenda factam recederc liceat".157

When, therefore, the South African courts started looking for a basis upon which to grant disappointed creditors the right to rescind the contract, the traditional sources of Roman-Dutch law did not provide much inspiration. Not that great efforts were made to analyse these sources; for those were the days of the "pollutionists",158 who did not hesitate to draw on English law whenever that appeared to be convenient. The theoretical foundations of such reception were usually somewhat fragile: a scanty remark to the effect that the "general rule of English law and . . . of Roman-Dutch Jurisprudence" have always been the same159 could do the trick. It was blatantly wrong in the present case; but by the time the "purists" exposed such mistaken assumptions, the English doctrine had often firmly taken root. All one could do, under those circumstances, was to sort out the doctrinal confusion that almost invariably arose as a consequence of such a development and to integrate the new institution as harmoniously as possible into the framework of the Roman-Dutch ius commune. Obviously, recognition of a right of rescission on account of mora debitoris as such was a welcome event; but its English paraphernalia threw many established doctrines into disarray. More particularly, the requirements for the new right of rescission were frequently confused with the basic requirements for mora debitoris and the relationship between the concept of "time is of the essence of the contract" and the rule of "dies interpellat pro homine" became as obscure as that between interpellatio and a notice of rescission.160 A particularly extravagant approach was adopted in a line of cases starting with the decision in

Federal Tobacco Works v. Barron & Co.:161 failure to deliver within a reasonable time can lead to a right of rescission even though (a) no specific date was fixed in the contract (i.e.: there is no mora ex re),

157Commentarius ad Pandectas, Lib. XIX, Cap. I, XXI; cf. further Van Zijl Steyn, op. cit., note 72, pp. 95 sqq.; De Wet en Yeats, p. 148.

158On the South African bellum iuridieum — concerning the proper sources of the common law—between pollutionists, purists, antiquarians and pragmatists, see Reinhard Zimmermann, "Synthesis in South African Private Law: Civil Law, Common Law and Usus Hodiernus Pandectarum", (1986) 103 SAL] 259 sqq.

159Cf., in the present context, Mitchell v. Howard Farrar & Co. (1886) 5 EDC 131 at 140 (per Barry JP). Generally cf. Reinhard Zimmermann, "Die Rechtsprechung des Supreme Court of the Cape of Good Hope am Endc der sechziger Jahre des 19. Jahrhunderts", in: Huldigingsbundel Paul von Warmelo (1984), pp. 286 sqq. In other cases relating to the right of rescission on account of mora Pofhier has been referred to; cf. Radue v. Kitsch 1920 OPD 181

at 186; Lewis & Co. v. Malkin 1926 TPD 665 at 670.

1611 Cf, for example, Wehr v. Botha 1965 (3) SA 46 (A) at 59 sqq.; Stapleford Estates (Ply.) Ltd. v. Wright 1968 (1) SA 1 (E) at 3F ("Where time is not of the essence, a party may clearly make it so by placing the other party in mora").

161 1904 TS 483; cf further Benoni Produce & Coal Co. Ltd. v. Gundelfinger 1918 TPD 453; Graf& Co. v. Bassa (1925) 46 NLR 2, and other decisions; cf. also Broderick Properties Ltd. v.

KowM962(4) SA 447 (T) (on which, see De Vos. (1970) 87 SAL] 314 sqq.; A.J. Kerr. (1978) 95 SAL] 143 sqq.).

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(b) no interpellatio occurred (i.e.: there is no mora ex persona) and (c) no notice of rescission was given to the debtor (i.e. time was, strictly speaking, not made "of the essence" of the contract). For a long time, mora debitoris could thus be described as "een van die verwaarloosde onderdele van [die Suid-Afrikaanse] reg",162 characterized, as a result, by "endless controversy"163 and "complete . . . confusion".164 Today it is widely recognized11"15 that a right of rescission can arise only where the debtor is guilty of mora. Where no time for performance has been specified, an interpellatio is therefore required. In addition, the contract must either contain a lex commissoria or time must be made "of the essence" by way of a notice of rescission.16r' The lex commissoria does not have to be expressly agreed upon. Where a specific time has been fixed by the parties and where this time, in their view, is essential for the performance of the contract (as is, for instance, usually the case in commercial transactions), it may be read into the transaction.167 A notice of rescission is required whenever there is neither an express nor an implied lex commissoria; that is, irrespective of whether we are dealing with mora ex re or mora ex persona. In the case of mora ex persona it may be combined with the interpellatio, but conceptually the two declarations have to be kept apart.168-169

IV. IMPOSSIBILITY OF PERFORMANCE AND BREACH OF CONTRACT

1. Breach of contract in Roman law

What about the other forms of breach of contract? We have seen that, according to the formulary procedure of classical law, the answer

162Van ZijI Steyn, op. cit., note 72, p. 1.

163j.R. Harker, "The Nature and Scope of Rescission as a Remedy for Breach of Contract

in American and South African Law", 1980 Ada Juridica 75. De Vos, (1970) 87 SALJ 312 sq.

As to what follows, see W. dc Vos. (1970) 87 SALJ 304 sqq.; idem, "Aspekte van mora debitoris", (1978) 41 THRHR 252 sqq.; De Wet en Yeats, pp. 148 sqq.; Marker. 1980 Ada Juridica 72 sqq.; also Van Zijl Stcyn, op. cit., note 72, pp. 103 sqq. As far asjudicial pronouncements are concerned, the decisions in Nel v. Cloete 1972 (2) SA 150 (A) at 159 sqq. and Greenfield Manufacturers (Temba) (Pty.) Ltd. v. Roylon Electrical Engineering (Pty.) Ltd. 1976

(2) SA 565 (A) at 568 sqq. are of particular interest.

166The term "notice of rescission" is somewhat misleading, since its effect is not (yet) the rescission of the contract; it merely creates the right for the creditor to rescind once the period set for performance has elapsed; cf. De Vos, (1970) 87 SALJ 310; Harker. 1980 Ada Juridica 77.

167These are the cases where, in English law, time is presumed to be "of the essence" even though no notice of rescission has been given.

168Cf. Nel v. Cloete 1972 (2) SA 150 (A) at 162D-164D; Ponisammy v. Versailles Estates (Pty.) Ltd. 1973 (1) SA 372 (A) at 387H-389D; W. de Vos, (1978) 41 THRHR 258 sq.

169For details of the nature of rescission (resolution, Rikktritt) as a remedy for breach of contract in modern law (how does it work? what are its effects?), c(. Treitel, "Remedies for Breach of Contract", in: International Encyclopedia of Comparative Law, vol. VII, 16, nn. 143 sqq.; Hans G. Leser, Der Riicktritt vom Vertrag (1975); idem, "Losung vom Vertrag", in: Recht und Rechtserkenntnis, Festschrift fur Ernst Wolf (1985), pp. 373 sqq.; Harker, 1980 Ada Juridica 61 sqq.

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depended on the type of action available to the creditor. The device of a perpetuatio obligationis was necessary in order to establish the liability, under the condictio, of a promisor who was responsible for the fact that the object of performance could no longer be transferred. But for the perpetuatio obligationis, the debtor of a certum dare obligation would have been released whenever performance became impossible. The position was different in the case of obligations for an incertum. Here the judge had to determine "quidquid dare facere oportet (ex fide bona)", which means that the debtor could be condemned in id quod interest irrespective of whether the object of performance still existed, provided only that the failure to perform (properly) was attributable to him according to whatever standard of liability appeared reasonable ("oportet ex fide bona") under the circumstances. In other words: a promisor automatically became free if the object of the stipulation was destroyed; as a result of the perpetuatio obligationis, however, he was liable for the value of that object, if he had culpably destroyed it. The vendor under a contract of emptio venditio, on the other hand, was liable for id quod interest, if he had made transfer of the object of the sale impossible or if he was guilty of any other form of breach of contract. Where he was not to blame for not performing (properly), however, it could hardly be said that he "ought to do or to give ex bona fide", and the actio empti was therefore unsuccessful.17" If the liability of the stipulator (for the value of the object) was (dogmatically) a somewhat artificial exception to the rule, the liability of the vendor flowed naturally from the basic principles governing bonae fidei iudicia.

2. Breach of contract under the ius commune

By the time of Justinian the procedural basis for these kinds of distinctions had fallen away; the formulary system had long since been abandoned and in its place the post-classical cognitio procedure reigned supreme. All claims were now adjudged from the point of view of aequitas,171 and thus, irrespective of whether a specific object or what the classical lawyers had termed an "incertum" was owed, irrespective also of the way in which the debtor had failed to comply with his contractual duties, he could now ultimately be condemned to id quod interest.172 It was therefore essentially the regime applicable to bonae fidei iudicia that survived. The perpetuatio obligationis had lost its function, but was, nevertheless, still incorporated into the Corpus

1'" In the result, therefore, the vendor became tree. Could he still demand payment of the purchase price or was the purchaser released from his obligation too? Or. in other words: who had to carry the risk of accidental destruction of the mc-rx? The answer is provided by the rule "periculum est emptoris": ct. supra, pp. 28) sqq.

171Cf. supra, p. 548. note 10.

172Cf. e.g. Kaser, RPr II, p. 357.

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The Law of Obligations

Juris Civilis173 and it has, not surprisingly, puzzled subsequent generations of lawyers.174 By and large, however, Justinian's codification had settled the problem of liability for breach of contract and from the days of the glossators down to the first half of the 19th century the basic principles remained unchallenged. More particularly, apart from mora debitoris, no specific types of breach of contract were singled out and dealt with separately. The debtor was liable for id quod interest (or, in the terminology coined by the glossators, the "interesse"),175 and supervening impossibility due to the destruction of the object of performance no longer automatically terminated his liability. Nonperformance on account of supervening impossibility therefore created no further problems than any other kind of breach of contract. What mattered was simply whether the debtor had complied with his contractual obligations and, if not, whether his failure to perform (properly) was attributable to his fault;176 hence the emphasis throughout the various periods of the ius commune on the subjective requirements for liability for breach of contract and the attempts to analyse, refine and systematize the various degrees of culpa (in the broad sense of the word).177 For a typical formulation of the prevailing doctrine, we may refer to the Codex Maximilianeus Bavaricus Civilis (1756), where it is crisply stated that "dolum, culpam vel casum in conventione praest[arej" means as much as to be liable for the loss arising through the contract due to the malice or negligence of one of the contracting parties or due to some unforeseen accident.178 Specific objective requirements for liability are not mentioned, and not even mora debitoris is specifically singled out. Following the pattern of the ius commune, too, is the French code civil. Its art. 1147 refers to "inexecution", a broad concept which covers all forms of breach of contract (that is, those cases where one of the parties "tie satisjera point

174 Take, for example, the situation in South African law. According to W.A. Ramsden,

Supervening Impossibility of Performance in the South African Law of Contract (!985), pp. 55 sqq., perpetuatio obligationis obtains in case of impossibility (due to the fault of the debtor) and mora debitoris. De Wet en Yeats refer to perpetuatio obiigationis only with regard to mora (p. 148); cf. also Van Zijl Steyn, op. cit., note 72, pp. 90 sqq. Others do not refer to perpetuatio obligationis at all.

Dilcher, Leistwtgsstorungen, pp. 120 sqq.; cf. further Hermann Lange, Schadensersatz und Privatstraje, pp. 13 sqq., 100 sqq.

17(1 During the time of the usus modernus, liability for damages arising as a consequence of deficient performance ("positive Vertragsverktzung"; cf. infra, pp. 812 sq.) tended to be based on the lex Aquilia rather than on contractual principles: cf. Harting, op. cit.. note 43, pp. 65 sqq.; Kaufmann, Lex Aquilia, pp. 46 sqq., 110 sqq.; Going, p. 442 and infra, p. 1024.

177 Dilcher, Leistungsstontngen, pp. 17 sqq.; Hoffmann, Fahrlassigkeit . pp. 35 sqq.

I7K IV 1 § 20. Praestatio casus refers to the case of a casus quern culpa praecessit, i.e. liability for casus where there has been either culpa praecedens or mora praecedens. Cf. generally Dilcher, Leistungsstorungen, pp. 109 sqq.; Stephan Kuttner, Kanonistisdte Schutdtehre von Gratian bis auj die Dekrctalcn Cregors IX (1935), pp. 185 sqq. The culpa praecedens doctrine is clearly related to the concept of versan in re illicita.

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a son engagement").179 The debtor is liable wherever such nonperformance is not due to vis maior or casus fortuitus.180

3. The notion of impossibility under the ius commune

What has been said so far does not, of course, mean that the notion of impossibility of performance was unknown or entirely irrelevant. First of all there was, as we have seen, the problem of initial impossibility of performance (impossibilium nulla est obligatio).181 Secondly, the trend towards specific performance must be kept in mind. Wherever the creditor (contrary to the classical Roman omnis condemnatio pecuniaria) was given the right to enforce performance in forma specifica,182 an exception had to be recognized for cases where such performance had become impossible. If the object that was to be transferred had been destroyed, the creditor could, as a matter of course, claim compensation only in money.183 And thirdly: where the object of performance had been accidentally destroyed and where the resulting impossibility was therefore not attributable to the debtor, the latter was seen to be released from his obligation. "Debitor speciei liberatur casuali interitu rei" became the general principle of the ius commune:184 an extension to bonae fidei contracts (especially to the contract of sale) of D. 46, 3, 107, a statement by Pomponius relating to verborum obligationes.185 Nevertheless, however, neither the interims rei nor the concept of impossibility featured as a general systematic category in the law relating to breach of contract. If the object of performance was accidentally destroyed, the debtor's obligation fell away. If the debtor was responsible for the destruction, he was liable for breach of contract; but he was liable in the same way and according to the same principles as wherever else he had failed to comply with his contractual duties. Culpa (with its various grades) and casus remained the central categories for the determination of the debtor's liability, not the specific type of breach of contract the debtor had committed.

4. Friedrich Mommsen's impossibility doctrine

Non-German readers will be wondering why this point needs emphasizing. The reason is that in the course of the 19th century the

179 Art. 1184 code civil. Art. 1147, however, also mentions "retard" (mora debitoris) as a special form of breach of contract. Cf. further e.g. Zwcigert/Kotz, pp. 213 sqq.; Nicholas,

FLC, pp. 193 sqq. 1H() Am. 1147 sq.

lKI Cf. supra, pp. 687 sqq. 1Я2 Cf. supra, pp. 772 sqq.

1H3 Wollschlager, Umnoglichkeitslehre, pp. 41 sq. As he points out, the crucial question for the authors of the ius commune was a different one: may a vendor (such as the debtor under an obligatio faciendi—nemo potest praecise cogi ad factum!; cf. supra, pp. 774 sq.) discharge his obligation by paying the interest, i.e. is he able to force the creditor to accept a monetary compensation in the place of specific performance, even where the latter is still possible?

18 Dilcher, Leistungsstorungen, pp. 185 sqq., Wollschlager, Utnndqlidikeitslehre, pp. 42 sq. 1H5Cf. supra, note 7.

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810 The Law of Obligations

whole perspective changed considerably. This was due, essentially, to a book by Friedrich Mommsen,186 brother ot the famous historian and Nobel prize winner, Theodor. He187 superimposed a concept of "impossibility of performance" on the sources, which covered all cases in which the debtor was unable to perform: non impleat quia non potest (as opposed to quia non vult).188 Impossibility became a very broad conceptual abstraction, a common systematic denominator for a whole range of situations. Thus, Mommsen distinguished, inter alia, between initial and supervening, natural and legal, absolute and relative, objective and subjective, permanent and temporary, complete and partial, apparent and "real" impossibility.189 The legal consequences in a given situation depended, in the first place, on its appropriate niche within this typology of "impossibilities". It was one of the consequences of this new approach that the category of "supervening impossibility" became the essential dogmatic cornerstone of the law relating to breach of contract.

Mommsen's book is characterized by that abstract and excessive conceptualism which is so typical of pandectist writing. It forced the sources into a scheme which was alien to the Roman lawyers and which, today, fails to appeal to legal historians and modern lawyers alike. It would probably have been largely forgotten, had it not managed to impress the most influential of the pandectists, Bernhard Windscheid19Oand, through him, the fathers of the BGB.lyi If we look into the German codification, we find the following rules:

5.Supervening impossibility in modern German law

(1)If performance becomes impossible owing to circumstances for which the debtor is not responsible, his obligation falls away.192 This

rule has taken the place of the old tenet of "debitor speciei liberatur casuali interim rei"m. It is formulated more broadly than the latter,194 since it refers not only to obligationes ad dandum but also to

obligationes ad faciendum. Obligationes ad faciendum, as will be

1Hfi Die Unmoglichkeit der Lei stung in ihrem Eittfliiss aufohligatorische Verhaltttisse (1853).

I M 7 On the roots of his ideas in the tradition of both the ius commune and (particularly) the law of the Age of Reason, see Wollschlager, Unmoglidikeitstehre, pp. 75 sqq., 118 sqq. On the Prussian General Land Law, which for the first time attributed central importance to the concept of impossibility within the law relating to breach of contract, see Wollschlager, pp. 106 sqq.

isa por t]^s alternative cf. Lauterbach, as discussed by Wollschlager, Untnoglichkeitslehre, pp. 72 sq.

1H9 Cf. the categories listed and discussed by Wollschlager, Unmoglichkeitslehre, pp. 125 sqq.

™ Windscheid/Kipp, §§ 264, 315, 360.

191Wollschlager, Unmoglichkeitslehre, pp. 167 sqq.

192§ 275 BGB.

193Cf. supra, p. 809.

144 And art. 1302 code civil.

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