If, in exchange for the benefit conferred upon the defendant, the defendant gives something of value to the plaintiff which the plaintiff, when he discovers his mistake, is able to return in specie, it is not against conscience for the defendant to retain the benefit received by him until such restitution is made:
Levy v. Terwilliger, 1881,10 Daly (N. Y. C. P.) 194: Action to recover $150 paid by the plaintiff's agent to the defendant for a safe which the agent mistakenly supposed the plaintiff had agreed to buy from the defendant. As a matter of fact the plaintiff had agreed to buy a safe from another dealer of the "As between the debtor and the original creditor the difference in amount between the two debts represents what in conscience should be paid by the one to the other. And the fact that in our system of law one claim does not extinguish the other, and must be pleaded, not as payment, but by way of set-off or counter-claim, does not prove that a creditor receiving in such circumstances, not the amount of his debt less the set-off, but the entire amount of his claim, has not in conscience received more than he should keep." same name. The defendant, misled by the action of the plaintiff's agent, had shipped a safe to the plaintiff. C. P. Daly, C.J. (p. 199): "It certainly is not against conscience that the defendant should, in this case, retain the price paid to him after having parted with the safe, when the plaintiff, through whose act and negligence it was shipped, has never made any effort to get it from the vessel and restore it to the defendant, but without doing or offering to do anything to repair what he himself brought about, asks the court to compel the defendant to restore to him the $150." 1
1 1786, 1 Term R. 285.
2 See Keener, "Quasi-Contracts," p. 51:
If that which the plaintiff receives from the defendant is of no value or advantage to the defendant whatever, its return is unnecessary.2 But it has been held that a grantee who would recover money paid for a conveyance of land under a mistake as to the grantor's title must tender a reconveyance, since otherwise any title that the grantor might subsequently acquire would vest in the grantee,3 and likewise that one who would recover land exchanged for mining stock must return the certificates of stock, if genuine, although the stock is of no intrinsic or market value.4
What if the benefit received by the plaintiff cannot be restored to the defendant in specie? Suppose, for instance, that the benefit consists of goods which the plaintiff sells or consumes before he learns of his mistake. Or, suppose that the benefit consists of services rendered - something which cannot be restored in specie under any circumstances. It is only fair, in such cases, to allow the plaintiff to recover to the extent that the benefit received by the defendant exceeds in value that received by the plaintiff. Such is the law,1 though where the action for restitution is employed not to recover benefits conferred by mistake but as an alternative remedy for the breach of a contract, it is held, by the weight of authority, that if the plaintiff cannot place the defendant in statu quo he cannot recover (post, Sec. 265).
1 Also: Lemans v. Wiley, 1883, 92 Ind. 436, 441, ("This note is not shown to have been a worthless thing, and we know of no rule of law or equity which will sanction her holding it, and recovering of appellant what she paid for it."); Coolidge v. Bingham, 1840, 1 Met. (Mass.) 547, (a genuine note with forged indorsements); Northampton Nat. Bank v. Smith, 1897, 169 Mass. 281; 47 N. E. 1009; 61 Am. St. Rep. 283, (check which bank had been instructed not to pay).
2 Kent v. Bornstein, 1866, 12 Allen (Mass.) 342, (counterfeit bill); Brewster v. Burnett, 1878, 125 Mass. 68; 28 Am. Rep. 203, (counterfeit U. S. bonds); Martin v. Home Bank, 1899, 160 N. Y. 190; 54 N. E. 717; aff. 30 App. Div. 498; 52 N. Y. Supp. 464, (valueless check); Paul v. City of Kenosha, 1867, 22 Wis. 266; 94 Am. Dec. 598, (void bond issued by defendant).
3 Moyer v. Shoemaker, 1849, 5 Barb. (N. Y. Sup. Ct.) 319, 322.
4Bassett v. Brown, 1870, 105 Mass. 551.