The Concept of Non-Contractual Obligations

 
MüKo/
Lieb
(fn 60) § 812, 
[201]. 
96
Englard
(fn 85) [129].
97
MüKo/
Lieb
(fn 60) § 812, [210], with further references. Similar considerations can also be 
relevant in case of a transfer of property. A Swiss case shows this nicely: the claimants‟ father had 
sold his shop under value to the defendant in the expectation of a future marriage between his 
daughter and the defendant. When the father died and the relationship between the couple came to an 
end before marriage, the claimants were granted a claim for what the defendant had received 
gratuitously. Yet this was not determined on the basis of the shop‟s objective value, but on the basis 
of what the parties regarded as an adequate price among friends. The court assumed that the father 
would have sold his shop to his future son-in-law below its objective value even if he did not 
actually want to make a gift to him: BGE 82 II 430, 437 ff (9 October 1956). 
98
See above II.A. 
99
As evaluated between the parties; see above fn 97. 
100
See the references above fn 94. In all these cases, in which the courts awarded a claim to the 
disappointed claimant, there had been an agreement between the parties, or at least an understanding, 
that the services were not rendered for nothing. Even if there was no such agreement, it may be fair 
to imply a corresponding condition; cf RG (18 January 1923) 78 Seufferts Archiv für die 
Entscheidungen der obersten Gerichte in den deutschen Staaten (SeuffA), 203 ff, no 124: the 
claimant had given most of his (quite substantial) property to the defendant, his wife, to make her 
return to the common household.

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19 
enrichment, which is impossible to measure independently of the parties‟ 
agreement).
A different group of cases appears even more problematic. These cases 
concern contractual agreements where one party has been motivated by some 
supervening motive that did not become part of the contractual agreement although 
it was known by the other party.
101
The claimant may have donated or sold a house 
at favourable conditions to a nephew on the basis of an expectation or hope that the 
nephew would marry and move into the house with his family.
102
Or one party paid 
damages on the basis of a disappointed expectation that the recipient would abstain 
from filing a criminal case against his wife.
103
According to the principles of 
contract law, such mistakes regarding the motive of one contracting partner are 
normally immaterial – at least as long as they have not been caused by the other 
side or amount to a relevant change of circumstances,
104
or can be interpreted as an 
(implied) pre-condition of the contractual agreement.
105
In fact, the law does not 
normally allow a young man to reclaim his gifts to a maiden rejecting his advances. 
Here, it is unnecessary to discuss the relevant contract law policies in more detail. 
The more important point is that applying the 
condictio ob rem
in such a case 
typically amounts to nullifying these policies. Either there has been an agreement 
between the parties with regard to the claimant‟s motive: then the question of 
breach of contract arises. Or there has been no such agreement: then the rules on 
mistake, fraud, or changed circumstances apply.
106
c) Some results 
All in all, it must be maintained that all these cases should be decided on the basis 
of contract law principles. Even if many legal systems treat them within the law of 
unjustified enrichment, they are ultimately contractual in nature.
107
Discussing such 
cases from the non-contractual perspective of unjustified enrichment endangers the 
integrity of contract law.
108
Hence, large parts of the modern law of enrichment 
101
See from Germany RGZ 132, 238, 242 (30 March 1931); BGH (15 March 1990) [1990] 
Wertpapier-Mitteilungen (WM) 1583, 1585: purchase of goods at a price exceeding their market 
value in expectation of being rewarded for this concession with a valuable contract for services. 
102
BGE 82 II, 430 ff (9 October 1956). The Austrian OGH has also allowed a claim for the 
maintenance that one partner provided for the other in expectation of a future marriage: OGH SZ 40, 
44 ff, no 15 (2 February 1967); OGH SZ 42, 286 ff no 94 (23 June 1969).