The Concept of Non-Contractual Obligations

Linoleumrolle
). 
37
Indeed, it has – rightly – even been omitted in the comparative study on pre-contractual liability by 
John Cartwright 
and 
Martijn Hesselink
, although this study is fact-based and descriptive, rather than 
doctrinal in approach: (fn 25) 15 f. 
38
See 
Kötz 
(fn 1) v, viii. 
39
See below at fn 127.  
40
Zimmermann
(fn 4) 834 ff. 
41
Specifically, the action (
condictio
) was originally introduced as a means of pursuing contractual 
claims resulting from a formal stipulation or from a loan (
mutuum
); see 
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, 164 ff; 
M Kaser/K Hackl
, Das Römische Zivilprozeßrecht (2nd edn 1996) 111 ff; 
Zimmermann
(fn 4) 835 ff. Yet also the 
condictio causa data non secuta
(C 4, 6; D 12, 4), which is 
today classified within the law of unjustified enrichment, was originally contractual in nature if 
qualified from a more functional perspective: this action concerned agreements that were not 
acknowledged as legally binding as such, but were regarded as a valid basis of transfer (
causa
) if 
they were honoured by both parties. Here, if one party performed on the basis of such an agreement, 

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8 
unjustified enrichment is about unwinding contracts.
42
Even if these obligations 
might well be explained on the basis of a conception of corrective justice, they are 
surely not meant to protect individual property rights. In the following two sections, 
the concept of non-contractual obligations will therefore be described in more 
detail: firstly, it will be asked whether all claims for an unjustified enrichment on 
the defendant‟s side should really be understood as non-contractual; secondly, the 
distinction and interplay between contractual and non-contractual,
 
or tortious, 
claims for damages will be analysed. 
1. Unjustified enrichment and contract law 
The Roman 
condictiones
are today the core of the modern civilian systems of 
unjustified enrichment, and – as under Roman law – these 
condictiones
, especially 
the 
condictio indebiti
, are widely used as a means of unwinding void contracts.
43
Indeed, if a contract was void – or was avoided later – it may be said that the parties 
have performed „without legal ground‟. From such a point of view, this is a typical 
case for a non-contractualclaim in unjustified enrichment.
44
Yet, seen from a more 
functional perspective, these 
condictiones
clearly pertain to a contractual context: 
they are a remedy for cases in which the law does not accept an agreement as 
legally binding.
45
Likewise the English remedy of restitution for failure of 
consideration is today regarded as a claim in unjustified enrichment, although it 
often assumes the function of a remedy for breach of contract.
46
It should be asked, 
therefore, why enrichment actions are used in some national systems for contract 
law purposes. 
Now, as it is often the case in the law, there is a rather simple historical 
answer to this question.
47
The Roman 
condictiones
were simply not based on the 
it had a 
condictio
if there was no counter-performance by the other party. See 
Zimmermann
(fn 4) 
843 f, with further references. When such agreements later became actionable on the part of the 
performing party, the