242 HARVARD LAW REVIEW. condition precedent. The prevention is the essential point. Until A has by taking action (which may consist either in doing what he would not otherwise have done, or in refraining from doing what he would have done) changed his position upon B's notice to him, there is no reason why the contract should be treated as broken merely by B's words alone. A should have no cause of action. The moment, however, that A takes such action and thus renders it impossible, inconvenient, or nugatory to perform his condition, at that time B has really prevented him from performing it. And B having made A's performance im- possible by his own act, cannot take advantage of its non-performance. We may show clearly that A has really been prevented by looking at the law of damages. It is a rule of that branch of the law that a party cannot enhance damages by his own act, and hence that after notice by the defendant that he rejects the contract, the plaintiff cannot go on and perform, or at least that if he does so he will not be per- mitted to recover damages. Clark v. Marsiglia, i Denio, 317 ; Dillon v. Anderson, 43 N. Y. 232; Black v. Woodrow, 39 Md. 217; Heaver v. Lanahan [Md.], 22 Atl. Rep. 263 ; Collins v. Delaporte, 115 Mass. 159 ; Danforth v. Walker, 37 Vt. 240, 40 Vt. 387; Cameron v. White, 74 Wise. 425. If this is a strict rule, then it is true that notice of rejection by B is a literal prevention of performance. This is the law to be laid down in cases of contracts for sale of land on an appointed day. If B sells off the land before that day, or otherwise makes it apparently impossible for himself to be able to perform as agreed, still A cannot sue for breach, or refuse to buy, if at the time appointed B is ready to sell, unless A has acted in some way during the meantime on the faith of B's apparent repudiation: Cf. James v. Burchell, 82 N. Y. 108. Assuming, then, that A assigns in his declaration a breach of an im- plied agreement by B not to prevent and to accept performance under the contract, it remains to be considered at what time he may bring action. It must be seen that if B has repudiated and A acted on that, the rights of the parties are fixed at that time, and no later retractation by B can alter A's right to sue. It is also evident that A's cause of action against B does not arise until some performance under the con- tract by B is due and has not been performed. Daniels v. Newton, 114 Mass. 530, contra to the English law as expressed on Hochster v. Delatour, also in 14 N. E. Rep. 436 and 8 So. Rep. 450. It seems that such failure to perform may consist either in not receiving and accepting *plaintiff A's performance, or in a failure by the defendant B to keep his principal promise. Hence A would have no right to bring action until December 1. The cases of marriage where B promised to marry A on December 1, and marries C on November 1 (42 N. Y. 246, Short v. Stone, Langd. Cases Con.), may perhaps be differentiated on this ground, that the mutual promises to marry imply further promises that in the mean- time the parties will occupy the relation of betrothed to one another, and B's marriage on November 1 constitutes a breach of the latter promise. Unless these cases can be explained in this way, they must be regarded as pure exceptions to what seems the true rule, that a plaintiff must wait until the time for defendant's performance comes before he can bring suit for breach of defendant's contract.
