Capacity

There are two basic reasons why a person may not be able to make a contract: Being under the age of 18 or not of "sound mind". In these situations a contract which involves a party who lacks "capacity" will either be void or voidable Void vs. voidable.

In Lucy v. Zehmer the two parties were drunk. Lucy tried to enforce the contract, which they had jotted down on a receipt from the bar where they were sitting, to sell a farm for $50,000. The court found that the contract was enforceable anyway.