Exception: However if a Mistake is about the qualtity of the subject matter then the courts will enforce the contract as it isn't enough to make the contract void.
CASE: "Leaf v International Galleries". In this case there was a sale of painting, which turned out to be fake. HELD: There was no operative mistake as it was over its value/quality.
2. Mutual Mistake: This involves a situation where the parties are mistaken but are at cross-purposes. It is usually regarding the identity of the subject matter.
CASE: "Raffles v Wichelhaus". In this case the contract was made for a quantity of cotton leaving from Bombay. However, there were 2 ships leaving Bombay called 'Peerless', 1 left in October and the other left in December. HELD: There was no common intention and was ... VOID as the parties were at cross-purposes.
3. Unilateral Mistake: This is where one party is mistaken, and the other party is taking advantage. This can happen in 1 of 2 ways:
1. Mistake where one party is aware and is taking advantage: If you know a party has made a mistake and try to take advantage the contract will be VOID.
CASE: "Hartog v Colin and Shields". In this case the parties made a contract regarding hare skins. The Hare skins were always priced per piece but the vendor had mistsakenly priced them per pound. HELD: Contract was VOID for Mistake as buyer took advantage knowing it should be per piece.