If it is clear that one party to a contract is going to be unable to perform it the other party should be excused from performing. The excuse is the same as in cases where a wilful intention not to perform is manifested. The party aggrieved is not going to get what he bargained for in return for his performance. It is immaterial to him, and it should be immaterial to the court whether the reason is because the other party cannot or because he will not do what he promised. Even if the prospective inability is due to vis major this should be true.74
72 Where the ground of non-performance is an actual breach of contract by the other party, it is an obvious consequence of the rule of common-law pleading which required the plaintiff to allege and prove his own performance, that he would fail if he had not duly performed, though the defendant had not manifested any election. Changes in modern pleading cannot have affected the substantive law on this point. Where the ground of nonperformance is repudiation or a prospective breach, there should be no difference for the essential nature of the defense is the same.
73See supra, Sec.Sec.083-688; Langdell, Summary of Contracts Sec. 177.
74 See supra, Sec.Sec. 877 el seq.