An unjust enrichment claim is generally understood to be a claim arising to correct an event or state of affairs consisting in the receipt or retention of a benefit by the defendant, and restitution is the remedy that corrects it by way of a transfer of the benefit or payment for it to the claimant. There have always been some claims of this sort: for example, the claim to recover a mistaken payment, or other invalid transfers of money or property; the claim to recover a prepayment or for payment for part performance, on the breakdown of a contract; and the claim for payment for a benefit conferred in the absence of a contract, for example in an emergency, as in the case of a salvor saving a ship foundering at sea. Until relatively recently, these various claims did not receive much attention in textbooks or university law courses, and in the case law they often seemed to be treated as a residual miscellany. Nowadays they are in the limelight. Many commentators have argued, or often just assumed, that the reason why these claims were overlooked for so long is that the courts failed to recognise a distinct category of the common law, a third private law category of restitution or unjust enrichment, analogous to contract and tort. In recent English cases, following the lead of the textbooks, the judges have indeed appeared to recognise such a category. But what is the significance of this? Is it just a matter of convenience in the exposition of the law and the administration of practice and teaching, which will help in a practical way to ensure that unjust enrichment claims are not ignored, or does it actually affect the law itself, and legal reasoning over unsettled law? In this substantial contribution to the literature, focussed on US law, Hanoch Dagan adopts a distinctive approach to this question. In Chapter 1, Dagan outlines his general approach to the common law, which he characterises as pragmatist in the tradition of American Legal Realism (pp. 3-10). One might take this to mean that he regards legal doctrine as just a "smokescreen" for the extraneous psychological or social factors that really determine how cases are decided. But Dagan denies this; he is not a sceptic about legal doctrine. The important point that he takes from Legal