Quasi contract. Legal fiction invented by common law courts to permit recovery by contractual remedy in cases where, in fact, there is no contract, but where circumstances are such that justice warrants a recovery as though there had been a promise. It is not based on intention or consent of the parties, but is founded on considerations of justice and equity, and on doctrine of unjust enrichment. It is not in fact a contract, but an obligation which the law creates in absence of any agreement, when and because the acts of the parties or others have placed in the possession of one person money, or its equivalent, under such circumstances that in equity and good conscience he ought not to retain it. It is what was formerly known as the contract implied in law; it has no reference to the intentions or expressions of the parties. The obligation is imposed despite, and frequently in frustration of their intention. See also Constructive contract.
In the civil law, a contractual relation arising out of transactions between the parties which give them mutual rights and obligations, but do not involve a specific and express convention or agreement between them. The lawful and purely voluntary acts of a man, from which there results any obligation whatever to a third person, and sometimes a reciprocal obligation between the parties. Civ.Code La. art. 2293. Black’s Law Dictionary 5th Ed. p. 293. See also. Equity and the Constitution, Chapter Four, Joseph Story’s Science of Equity, and the two types of equity, natural equity and civil equity. There is a difference.