What is Unjust Enrichment

That there exists a law of restitution concerned with reversing unjust enrichments is widely considered to be uncontroversial. However, the once orthodox view that unjust enrichment explains all instances of restitutionary liability is fast becoming a minority position. Indeed, the ability of ‘unjust enrichment’ to account for all restitutionary claims has been doubted by many of those who fought most strongly for its recognition as an independent head or source of liability, chief amongst these Professor Peter Birks. Because of this, while there is widespread acceptance that unjust enrichment plays some role within the law of restitution, there is considerable uncertainty as to what this exact role is, so much so that what is meant by unjust enrichment can be seen to be in doubt. Beginning with an examination of Birks’ understanding of unjust enrichment and the classificatory scheme into which it slots, this article addresses the question of what role a conception of unjust enrichment can and should play in presenting and justifying the law of restitution.