As a contract consists of a binding promise or set of promises, a breach of contract is a failure, without legal excuse, to perform any promise which forms the whole or part of a contract. It is immaterial for this purpose whether the failure in performance is great or small, or whether any damage has been caused.1 Any breach of contract gives rise to a right of action ; and at common law no judicial expression of the rights of the parties could be obtained until there had been a breach.2
When the time for performance of a promise has so far passed that substantial fulfilment of the promise is no longer possible, the obligation of the promisor changes its character. Even though the law could and did grant specific performance, so called, of all contracts, the performance enforced by the court would differ from that contracted for at least in being given at a later time than was agreed. The Civil law makes a distinction in terms between mora or delay in performance, and a breach in other respects than in time, of the duty to perform. The difference is not so sharply defined in English and American law, but is, nevertheless, implicitly observed in some distinctions which the law makes. The obligation to perform and the obligation to do so at a fixed time are regarded as two duties, rather than as one indivisible duty. Thus a promise to convey property which is enforced by equity is regarded as specifically enforced even though considerable time has elapsed after the date at which it was agreed that the conveyance should be made. Damages may be given for the delay as a separate matter. At law a promise to pay money is almost the only kind of promise which can be specifically enforced, and the common law in enforcing an obligation to pay an agreed sum of money 3 conceived that the promise itself continued in effect after the time fixed for its performance had elapsed. On the other hand, when a promise to deliver goods or do anything other than pay money is broken, the law substitutes for the obligation a right of action for damages.4
It should be observed, however, that this distinction between an obligation to pay money and an obligation to do other things is only applicable where the money is absolutely due. When money is promised in exchange for something else which has not been given, and where, therefore, no debt has arisen, a breach of the promise to pay the money for the performance to be exchanged for it is ground for the payment of damages, not for the recovery of the full sum promised. In such a case the same considerations are applicable as in the case of obligations to deliver goods or render services.