II. The Link between the Condictio ob Turpem Causam and the Condictio ob Iniustam Causam in the Digest

Comparing the Digest with the Codex on the condictio ob turpem vel iniustam causam, a striking difference may be noticed: while in the Digest the condictio ob turpem and ob iniustam causam are brought together under the same title, and have been amalgamated into one term "condictio ob turpem vel iniustam causam", in the Codex the two types of case are treated separately. The title C. 4.7 deals with the condictio ob turpem causam; here we find cases ob turpem causam as well as the in pari delicto rule. After C. 4.8, where the condictio furtiva is discussed, in C. 4.9 the condictio ob iniustam causam appears. However, it only appears in the title, which runs De condictione ex lege et sine causa vel iniusta causa. The texts of the constitutions in this title do not mention these terms any more. C. 4.9.1 deals with a case in which the condictio is used to claim back a loan even before the term of loan has elapsed; the fragment does not deal with a case of unjustified enrichment (the loan is valid), and hence is not our concern.185 The second fragment of this title states that a legal instrument which is invalid may be claimed from the creditor. In the third text, C. 4.9.3, <57> the condictio is granted for the recovery of fruits which were drawn and consumed by a mala fide possessor who knew he had no right to consume the fruits. This text, as we may conclude from parallel fragments in the Digest (see above C II 1), probably deals with a case ob iniustam causam. Finally, in C. 4.9.4, the pursuer is allowed to claim back a security given for a loan which was never paid out to the pursuer. Again, it is crucial to note that none of these texts deals with the violation of any legislation.

The Digest was compiled after the Codex had already been published;186 therefore the combination of the cases ob iniustam causam with ob turpem causam must be later than their combination with sine causa. The reasons for this systematic change can only be guessed at187, all the more since the one

185Cf. A II 1 b to the use of the condictio to claim back a loan. <57>

186Honsell/Mayer-Maly/Selb, Römisches Recht (4th ed., 1987), p. 46 with literature.

187Cf. also D. 12.7.5 De condictione sine causa, where a case is discussed which seems to concern a turpis causa, and which might therefore have been compiled in D. 12.5. However, according to the reasoning of Paulus it could be seen as a case of sine causa (although the classification sine causa was probably postclassical): non turpem causam...: non enim stupri, sed matrimonii gratia datam esse. The marriage, as a causa, never took place. One could reason that therefore the dowry money in question here was given sine causa. This might have been the reason for the law commission to file the text under this title. For a discussion of D. 12.7.5.1 see B II.

fragment actually appearing under the title De condictione ob turpem vel iniustam causam does not give a practical example but only makes the general statement that what is retained ex iniusta causa may be recovered with the condictio. A further finding is that, in the Digest, fragments in which an iniusta or non iusta causa is mentioned in the context of the condictio are mostly scattered between the different books of the Digest concerning the condictio, with one further mention in the book on marital donations. They are not systematically gathered under the title De condictione ob turpem vel iniustam causam.

It has been suggested188 that the condictio ob iniustam causam might have increased in importance after Theodosius II had turned every statutory prohibition into a lex perfecta in his lex non dubium (439 A.D.).189 Due to this provision, infringement of the law generally rendered a contract invalid.

However, nowhere does the lex non dubium mention the condictio ob iniustam causam or cases which could be related to it. The cases mentioned in Nov. Theod. 9 concern the provision that there is no action to enforce a contract if the contract is <58> illegal, but there is no case concerning the recovery of benefits already transferred. The suggestion190 that Theodosius II made use of the condictio ob iniustam causam where a lex perfecta was violated fails to provide any proof. On the contrary, given that there is no clear hint in the later Digest or the Codex that the condictio ob iniustam causam was operated at all in cases of statutory violations it is difficult to imagine how the provision of Theodosius II could have affected the condictio ob iniustam causam. In the Codex, which was compiled long after the lex non dubium had been enacted, the condictio causa data causa non secuta is reported as a claim to recover illegally paid money (C. 4.6.5).191 Looking at the cases where the condictio is operated on the grounds of an iniusta causa, the condictio ob iniustam causam rather seems to denote cases of encroachment on the private rights of the pursuer. This might explain why Justinian's law commission associated the condictio ob iniustam causam with the condictio ob turpem

188 D. Liebs, "The History of the Roman Condictio up to Justinian", in: N. MacCormick/P. Birks (eds.), The Legal Mind – Essays for Tony Honoré (1986), 163 (pp. 175 sq.); Zimmermann, The Law of Obligations, pp. 845 sq. note 77.

189Nov. Theod. 9 / C. 1.14.5.1 ...hoc est ut ea quae lege fieri prohibentur, si fuerint facta, non solum inutilia, sed pro infectis etiam habeantur, licet legis lator fieri prohibuerit tantum nec specialiter dixerit inutile esse debere quod factum est. <58>

190D. Liebs, "The History of the Roman Condictio up to Justinian", in: N. MacCormick/P. Birks (eds.), The Legal Mind – Essays for Tony Honoré (1986), 163 (pp. 175 sq.).

191Above C I 1. <59>