The Concept of Non-Contractual Obligations

I. Three fundamental ideas 
Today, a common source for such a meaningful concept of non-contractual 
obligations can be found on the basis of ideas that were once developed, by early 
natural lawyers, as a comprehensive theory of non-contractual obligations. Within 
the concept of restitution (
restitutio
), this theory comprised large parts of modern 
tort law and unjustified enrichment. Here, it is not necessary to give a complete 
presentation of this overarching conception of non-contractual obligations. It 
suffices to understand the three fundamental ideas, or basic theoretical elements, 
underlying this theory of 
restitutio
. The first one was of genuinely Christian, 
theological origin: it was the Augustinian principle that a sin cannot be forgiven 
unless the sinner has given back what had been taken away (
non remittetur 
peccatum nisi restituatur ablatum
).
15
Although this principle was originally based 
on the Biblical prohibition against theft (2 Mos 20,15), it was from early on 
understood very broadly, covering all kinds of damage done.
16
Today this principle 
the other articles in: 
id
, Responsibility and Fault (1999); 
HLA Hart/T Honoré
, Causation in the Law (2nd 
edn 1985) xlii ff, lxxvii ff; 
N Jansen
, Die Struktur des Haftungsrechts. Geschichte, Theorie und 
Dogmatik außervertraglicher Ansprüche auf Schadensersatz (2003) 119 ff, 136 ff.
 
11
See 
R Zimmermann
, Unjustified Enrichment: The Modern Civilian Approach (1995) 15
 
Oxford 
Journal of Legal Studies (OJLS) 403 f, 419 and passim; 
J Gordley
, Foundations of Private Law. 
Property, Tort, Contract, Unjust Enrichment (2006) 157 (and ff), 417 (and ff). 
12
On the terminology, and for an overview, see 
Zimmermann
(fn 4) 890; 
id
(1995) 15 OJLS 418 ff. 
13
K Larenz/C-W Canaris
, Lehrbuch des Schuldrechts, vol II/2 (13th edn 1994) 170; 
Zimmermann
(1995) 15 OJLS 418 f; 
Jansen
(fn 10) 477 ff; see also 
S Meier
, No Basis: A Comparative View, in: 
A Burrows/Lord Rodger of Earlsferry (eds), Mapping the Law. Essays in Memory of Peter Birks 
(2006) 343, 354 ff. 
14
Cf the comprehensive analysis and references in 
Schlechtriem
(fn 3) vol II, 81 ff.
 
15
Augustinus
, Epistola CLIII (ad Macedonium), no
 
20 (in: J-P Migne [ed], Patrologia Latina, vol 33 
[Paris 1861] col 653, 662); Decretum Gratiani,
 
C XIV q VI, c I; cf 
G Otte
, Das Privatrecht bei 
Francisco de Vitoria (1964) 64. 
16
Petrus Lombardus
, Sententiae in IV libris distinctae (Specilegium Bonaventurianum, vols 4 and 5, 

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4 
finds a more secular expression in the moral truism that one cannot expect to be 
socially acknowledged as a person without accepting one‟s responsibility towards 
fellow-citizens. 
The second fundamental element within the theory of 
restitutio
was of 
philosophical nature. It was the Aristotelian concept of corrective justice, which 
was introduced into the medieval discourse on 
restitutio
by Albertus Magnus and 
Aquinas.
17
These philosophers re-interpreted the duty to make 
restitutio
from the 
point of view of corrective justice (
restitutio est actus commutativae justitiae
).
18
As 
a result, the duty to make restitution was not only directed against the Lord, but 
primarily against one‟s fellow-citizens, and it was intellectually oriented towards 
the idea of equality: the wrongdoer had to make good all damage caused, and to 
restore all gains; yet, the victim should not get more than he had lost. Thus, the 
defendant‟s enrichment was not contrasted with the claimant‟s loss as a „causative 
event‟ triggering liability. The mere fact of some enrichment was seen as a legal 
problem. Rather, the legal argument always started from the claimant‟s loss, and the 
defendant‟s enrichment systematically and functionally corresponded to the concept 
of fault: it was a (weak) reason for imposing liability. 
The final fundamental element underlying the theory of 
restitutio
transformed this still rather abstract conception of justice into a body of juridically 
applicable rules. It was the idea, authoritatively established by the leading early 
natural lawyer Francisco de Vitoria, that all restitution is based on the infringement 
of individual (property) rights (
dominium
): 
omnis restitutio fundatur in dominio
.
19
This idea complemented the rather abstract notion of restoring equality. It served as 
a measure for determining whether there was a relevant inequality between two 
citizens. Not all interference with another person‟s interests would give rise to a 
duty to make restitution; it was always necessary that the claimant‟s – fairly widely 
conceived – sphere of protected interests had been infringed. Hence, a more and 
more elaborated legal conception of property rights and legally protected interests 
became the basis of 
restitutio
and thus of all non-contractual liability. 
Clearly, such a theory cannot simply be transplanted into modern law – not 
only because of serious „internal‟ problems within the original theory itself, but first 
of all, because a 16th century Catholic natural-law theory as such is dead history. 
Nevertheless, this theory reformulated principles of private law that were 
conceptually independent of the historical context of Late Scholasticism and that 
have remained good law throughout Europe. In fact, the theory of 
restitutio
strongly 
influenced the works of Grotius and Pufendorf who in turn initiated a revolution of 
private law thinking in Europe.
20
Although these authors did not make the institute 
1971/1981), lib III, dist XXXVII, cap
 
V; cf 
K Weinzierl
, Die Restitutionslehre der Frühscholastik 
(1936) 11 ff. 
17
Albertus Magnus
, Commentarii in IV libros Sententiarum (Opera Omnia, ed by Steph Caes Aug 
Borgnet, vols 25–30, Paris 1893-94) lib IV, dist XV, art XLII; 
Aquinas
, Summa theologica (SE 
Fretté/P Maré [eds], Opera Omnia, vols I-VI, Paris 1871-73) secunda secundae partis (II-II) q LXII, 
art I.
18
Aquinas
, Summa theologica II-II (no 17) q LXII, art I, resp
.
19
F de Vitoria
, Commentaria in secundam secundae (under the title Commentarios a la Secunda 
secundae de Santo Tomás, ed by V Beltrán de Heredia, 1932–1952) q LXII, art I, no 6. All later 
Spanish natural lawyers proceeded from this basic theoretical assumption. 
20
Cf 
J Gordley
, The Philosophical Origins of Modern Contract Doctrine (1991). 

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5 
of
 
restitutio
a systematic part of their systems of private law, they did accept the 
three fundamental principles underlying this theory. Thus, it has been shown 
elsewhere in detail that important aspects of European tort law, of unjustified 
enrichment, and of the law of damages substantially rely on principles developed 
within the framework of the theory of 
restitutio
.
21
Even today, non-contractual 
obligations rest on the three basic ideas of individual responsibility, corrective 
justice, and the protection of reliance in the integrity of one‟s rights and in the 
lawful and trustworthy behaviour of one‟s fellow-citizens. That these ideas govern 
the law of unjustified enrichment is evident. Yet the first idea is probably the main 
reason for not replacing, but rather complementing, the rather costly and inefficient 
system of tort law
22
with collective insurance systems. The second idea lies inter 
alia at the roots of the principle of full compensation also of non-material loss.
23
And the third idea explains why the abstract fact of the defendant‟s unlawful 
behaviour causing some damage is not enough to justify a claim for damages. All 
legal systems, including those not specifically distinguishing within tort law 
different classes of interests, make compensation dependent on the fact that the 
claimant cannot be expected to bear the loss him- or herself.
24
This can only be the 
case if the claimant is justified in relying on the integrity of the violated interest, 
including the lawful behaviour of fellow-citizens. Unearthing these three basic ideas 
thus promises to contribute to a better understanding of present law and toward 
common principles of a common European private law.