Consideration in English law
Consideration in English law is one of the four main building blocks of a contract. Consideration can be anything of value (such as an item or service), which each party to a legally binding contract must agree to exchange if the contract is to be valid. If only one party offers consideration, the agreement is not legally a binding contract. In its traditional form, expressed as the requirement that in order for parties to be able to enforce a promise, they must have given something for it (quid pro quo): something must be given or promised in exchange or return for the promise. A contract must be "met with" or "supported by" consideration to be enforceable; also, only a person who has provided consideration can enforce a contract. In other words, if an arrangement consists of a promise which is not supported by consideration, then the arrangement is not a legally enforceable contract. Mutual promises constitute consideration for each other. ("I promise you that I will do X, in consideration for which you promise me that you will do Y").