Ordinarily, to constitute a valid defense in an action for breach of contract the mistake must be a mutual one made by all of the parties to the contract. However, when the mistake is obvious from the face of the contract, knowledge of the mistake will be imputed to each party. Thus, a contract that by its terms designates a horse as the subject matter will be enforced unless both parties agree that a different subject matter was intended. On the other hand, if the same contract designates a pig as the subject matter in 99 paragraphs of the agreement, but mentions a horse in only one paragraph, a court will not force the defendant to sell his horse if it is obvious that the one paragraph contains an error.

Inside Mistake