The contract which is implied in law is always to pay the fair value of what has been received. The Latin words quantum meruit, meaning as much as it is worth, are therefore used to describe an action based upon an implied contract. To recover in quantum meruit accordingly means to recover the reasonable value, to be determined in the course of the action, of whatever has been furnished. It has already been explained that where there exists a valid and enforcable contract, on which both parties have the right to insist, no recovery can be had in quantum meruit for labor and materials furnished under the contract. This does not mean that where a contract once existed concerning such work and labor, or goods or materials, or concerning a part of it, an action in quantum meruit will never lie. There are various circumstances under which this action will lie, in spite of such an express contract. It sometimes happens that a contract is so altered that it is no longer ascertainable and is there-fore treated as not existing. In such a case an action on an im-plied contract can be maintained. If a partly performed contract is abandoned by agreement of all the parties to it, an action in quantum meruit will lie for the work or materials already furnished only in case the contract is what is known as an entire contract as distinguished from a divisible or apportionable contract. An apportionable or divisible contract is one susceptible of division or apportionment because of having two or more parts not necessarily dependent upon each other and not intended to be so dependent; as in the case of a contract for building several houses, where there is nothing in the contract itself or the circumstances to prevent singling out the part respecting any particular house, and treating it as distinct and complete of itself. Such a contract might be of such a nature that it would be obviously unfair to one party or the other thus to separate the parts, and to hold a party bound as to a portion without regard to the rest. A contract of this latter sort would be an entire contract, that is, a contract of which the terms, nature and purposes indicate an intention that each of its material provisions shall be dependent on all the rest. If, then, the contract which is abandoned be a divisible contract of which one or more complete divisions have been performed, the contract may be treated as governing those divisions and recovery may be had only under the contract. But if the contract be an entire contract it would not be fair then to hold the parties as bound in respect to a portion only, never contemplated as complete in itself. Their rights must therefore be settled on the theory of implied contract, the party indebted being answerable in quantum meruit only.

Where one party to a contract is ready and willing to perform, but is prevented from performing or from completing his performance by the act or fault of the other contracting party, the first party may recover on the contract, or he may elect to rescind the contract and recover in quantum meruit for the labor and materials employed. If the party prevented from performing elects to rescind the contract and sue in quantum meruit, the party at fault is required to pay whatever the real worth of the work and materials is proved to be, not, however, according to the general rule, giving compensation in excess of the contract price for the whole.

In an action in quantum meruit the architect's certificate is probably not necessary to recovery, although where the architect has pointed out defects in the work or material already employed and the builder claims to have remedied them, it may be practically necessary for the builder to show the architect's certificate stating that the defects have been satisfactorily remedied.