None of its rules are stated in terms of quasi-contract or the forms of action, and almost none are stated in terms of common law or equity.
Here is the whole law of quantum meruit--a phrase that survives from the days of quasi-contract and can be translated into plain English as "reasonable value" ([section] 31 cmt.
5) William A Keener, A Treatise on the Law of Quasi-Contracts (Baker, Voorhis and Co, 1893).
The opening words of the first substantive chapter in Keener, above n 5, 26 are illustrative: The recovery at law of money paid under mistake affords not only one of the most striking illustrations of the equitable nature of the quasi-contractual obligation, where the liability rests upon the doctrine of unjust enrichment, but also shows, in common with the other topics belonging to the law of Quasi-Contracts, how utterly foreign to the subject are the principles of the law of Contract.
34) p H Winfield, 'The American Restatement of the Law of Restitution' (1938) 54 Law Quarterly Review 529 (where it is stated at 529 that 'English lawyers cannot have their attention directed too often or too emphatically to this branch of the law'); P H Winfield, 'Equity and Quasi-Contract' (1948) 64 Law Quarterly Review 46; Sir P H Winfield, The Law of Quasi-Contracts (Sweet & Maxwell, 1952).
And the presence of restitution for cases of quasi-contract
seems less suspect and less marginal than the classics claimed--yet again raising the specter that private law is infused, through and through, with public decision making and a limited role for actual consent.