Where reformation is possible, it is generally the only remedy permissible, since the mistake of the parties related to their expression only, and to decree rescission and freedom from all bond would be an unnecessary violation of their intent. But where the error is in the substance of the bargain, not in its expression - that is where the mistake relates to the way the agreed terms will apply to the external world, rescission with restitution of whatever has been parted with, is the only relief possible, though this may be sought in a variety of ways appropriate for different situations, namely: -
86 Jackson v. Wolfe, 127 Ark. 54, 191 S. W. 938; Peters v. Priest, 134 Ark. 161, 203 S. W. 1042; Fickes v. Baker, 36 Cal. App. 129, 171 Pac. 819; Shears v. Westover, 110 Mich. 506, 68 N. W. 266; Powell v. Morisey, 98 N. C. 426, 2 Am. St. Rep. 343; Hout v. Hout, 20 Oh. St. 119; Dennis v. Dennis, 4 Rich. Eq. 307; Willey v. Hodge, 104 Wis. 81, 80 N. W. 75, 76 Am. St. Rep. 852.
87 Olmsted v. Olmsted, 38 Conn. 309; United States v. Cushman, 2 Sumn. 426, Fed. Cas. No. 14,908; Keith v.
Henkleman, 68 111. App. 623, affd. in 173 111. 137, 50 N. E. 692; State ex rel Frank v. Frank, 51 Mo. 98; Smith v. Allen, 1 N. J. Eq. 43, 21 Am. Dec. 33; Prior v. Williams, 3 Abb. App. Dec. 624; Wiser v. Blachly, 1 Johns. Ch. 607; Butler v. Durham, 3 Ire. Eq. 589; Neininger v. State, 50 Ohio St. 394, 34 N. E. 633, 40 Am. St. Rep. 674.
88 Gilmore v. Thomas, 252 Mo. 147, 158 S. W. 577; Edwards v. Boyle, 37 Okl. 639, 133 Pac. 233.
2. In case of any contract written or oral, one whose promise is still executory may promptly offer to return anything received by him, and if his offer is refused and he is sued for failure to perform his promise, may set up as a defence to an action at law or suit in equity the facts justifying rescission.
3. One who has paid money under a mistake justifying rescission may use in general assumpsit, or its modern local equivalent, on principles of quasi-contract for its recovery; and to a great degree similar redress is allowable for the recovery of the value of goods or services.
The character of mistake justifying relief should not differ, whatever tribunal or remedy may be appropriate to a particular case. The doctrines governing mistake have mainly, but not exclusively been developed in equity but at the present time the differences between the two jurisdictions on the subject tend to become confined to the propriety of a particular remedy and not to extend to the fundamental basis of right; though this result has not as yet been wholly achieved. Knowledge by one party that the other is under a mistake as to such a matter as would make the transaction voidable if the mistake were mutual, if accompanied by any circumstances deemed inequitable and perhaps generally without more, will have the same effect as mutual mistake in justifying rescission.89
89 Griswold v. Hazard, 141 U. S. 260, 35 L. Ed. 678, 11 Sup. Ct. 972, 999; Wyche v. Green, 26 Ga. 415; Shelton v. Ellis, 70 Ga. 297; McCormick v. Miller, 102 11I. 206, 40 Am. Rap. 577; Montgonery County v. American Emigrant Co., 47 la. 91; Freeman v. Groom, 172 N. C. 524, 90 S. E. 523; International L. Ins. Co. v, Stuart (Tex. Civ. App.), 201 S. W. 1068. See also
Simmons Creek Coal Co. v. Doran, 142 U. S. 417, 12 Sup. Ct. Rep. 239, 35 L. Ed. 1063; Medical Society v. Gil-breth, 208 Fed. 899; Campbell v. Hatchett, 55 Ala. 548; Webb v. Hammond, 31 Ind. App. 613, 68 N. E. 916. How far silence under such circumstances is fraudulent is considered supra, Sec.Sec. 1497-1499.