This section is from the book "The Law Of Contracts", by William Herbert Page. Also available from Amazon: Commercial Contracts: A Practical Guide to Deals, Contracts, Agreements and Promises.
If A, a party to a contract which is executory on his side, does not receive what he was promised by B in consideration for his promise, the question is presented whether A can use such facts as discharging him from liability upon his executory contract or whether he is still liable to B upon his covenants and his only remedy is an action against B for damages. If A can use such facts as a discharge, a failure of consideration is said to exist. Failure of consideration may assume either of two forms. (1) A may make his promise in consideration of an executory promise made to him by B and B's failure to perform such executory promise may then constitute the failure of consideration. (2) A may make his promise in consideration of the transfer to him by B of certain property or other legal rights which B agrees shall possess certain qualities and which proves not to possess such qualities. The doctrine of failure of consideration involves in some cases questions of fraud, misrepresentation or mistake. In other cases the question presented is primarily one of the power of equity to rescind contracts and conveyances.