This is particularly important in terms of the lack of overlap between the condictio indebiti and condictio causa data causa non secuta.
He argues that Roman law, from which the "civilian" systems are derived, was partly absence of basis--the condictio sine causa--but also had claims for mistake (condictio indebiti) and failure of consideration (condictio causa data causa non secuta).
(25) It also explains why it is not wholly irrational for Scots (26) and South African law (27) to have a requirement the claimant show a mistake in their condictio indebiti actions; the mistake requirements are not bizarre imports from English law, but have a respectable Roman vintage, (28) and the error requirement, which must be a mistake as to liability, is tied into the requirement that no debt or other valid obligation to pay exists.
(63) She reanalyzes the condictio indebiti in terms of different unjust factors, including failure of consideration.
He argued that in South Africa under the condictio indebiti, the mistake must be a mistake as to liability; in English law it can be a mistake as to pretty much anything at all, so long as it causes the payment.