IS ABSOLUTE DUTY TO PERFORM DISCHARGED?:
Contractual duties will be discharged if it has become impossible to perform them.
-- impossibility must be objective, duties could not be performed by anyone;
-- impossibility must arise after the contract has been entered into; if impossibility existed at time of contracting, then the problem is one of contract formation, namely, whether the contract is voidable because of mistake.
-- if the contract is discharged because of impossibility, each party is excused from duties arising under the contract that are yet to be fulfilled, either party may sue for rescission and receive restitution of any goods delivered, etc.
-- if the performance is made only partially impossible, the duty may be discharged only to that extent of the impossibility
-- temporary impossibility suspends contractual duties; it does not discharge them; not however that if the burden on either party to the contract would be substantially increased or different from that originally contemplated.
-- if part performance has been renered by either party prior to the existence of the facts leading to impossibility, that party will have a right to recover in quasi-contract at the contract rate or for the reasonable value of his performance
death or physical incapacity: of a person necessary to effectuate the contract serves to discharge it.
supervening illegality: often treated as a form of impossibility
subsequent destruction of subject matter or means of performance: contractual duties will be discharged, note however, that this destruction must not have been the fault of either party; destruction of the subject matter will render a contract impossible only if the very thing destroyed is necessary to fulfill the contract, if the thing destroyed is not actually necessary, impossiblity is not a defense; the rules relating to discharge because of destruction of the subject matter will not apply if the risk has already passed to the buyer.