Frustration of purpose
（重定向自Frustration of contract）
In the law of contracts, frustration of purpose is a defense to enforcement of the contract. Frustration of purpose occurs when an unforeseen event undermines a party's principle purpose for entering into a contract, and both parties knew of this principle purpose at the time the contract was made. Despite frequently arising as a result of government action, any third party (or even nature) can frustrate a contracting party's primary purpose for entering into the contract. This concept is also called commercial frustration.