Home > West's Encyclopedia of American Law > Impossibility

A legal excuse or defense to an action for the breach of a contract; less frequently, a defense to a criminal charge of an attempted crime, such as attempted ROBBERY or murder.

Historically, a person who entered a contract was bound to perform according to his or her promised duties, regardless of whether it became impossible to do so. Thus, early U.S. courts did not recognize the defense of impossibility of performance. Courts noted that if the parties to a contract had desired to take into account any events that may develop after they reached an agreement, then they should have accounted for such contingencies in the contract.

As contract law developed over the twentieth century—and in response to increasing commercial activities—courts began to recognize impossibility as a valid defense to an action for breach of a contract. This...