Abstract

The current English discussion on the ‘at the expense of ’ element proceeds on the assumption that it has the same meaning in all kinds of unjust enrichment claims. The same assumption was made under the unitary doctrine in Germany after 1900. However, problems in defining the ‘at the expense of ’ requirement led to the development of the doctrine of separation, which prevails today. Its essential feature is that the elements of ‘at the expense of ’ and ‘without legal ground’ have different meanings in the different condictiones. A recurring problem is how to explain the exclusion of restitution in cases of incidental benefits. It may be argued that there is a legal ground, that the benefit has not been at the claimant’s expense, or that the defendant did not receive a benefit at all. Those who deny an enrichment at the claimant’s expense, however, have to be aware that this explanation holds true only if no performance is involved.