6. Consideration

Currie v Misa describes consideration as a right, interest, profit or benefit to one side, or a forbearance, detriment, loss or responsibility given or undertaken by the other. The modern way of putting it is that consideration must move from the promisee. It need not move to the promisor.

It must be sufficient, meaning it has some value in the eye of the law, but it need not be adequate. The court does not ask whether the bargain was a good one. Thomas v Thomas is the familiar point: a nominal payment can be enough if it was genuinely the price of the promise.

Past consideration is no consideration. Something already done, before the promise and not at the promisor's request, cannot buy a later promise. There is an exception where the act was done at the request, payment was in the parties' contemplation, and the later promise only fixes the amount. Pao On v Lau Yiu Long is the modern statement of that exception, and commercial pressure is discussed in the same neighbourhood of cases.

Performing an existing public duty, or a duty you already owe the other party under a contract, is not fresh consideration. Stilk v Myrick: sailors who finished the voyage after desertions were doing what they had already promised. Hartley v Ponsonby is the contrast: so many men had gone that the remaining voyage was a different and more dangerous job. Extra pay was earned. Williams v Roffey Bros later softened the practical result where one side obtains a real benefit by promising more money to secure performance of an existing contract, but the starting point remains Stilk.

Part payment of a debt

Part payment of a debt, without more, does not discharge the whole. Pinnel's Case, affirmed in Foakes v Beer: a lesser sum cannot be satisfaction of a greater sum already due. Mrs Beer could still sue for the interest even after she had agreed to take instalments of the principal.

There are ways round it. Payment of a smaller sum earlier, at a different place, or with something added (a horse, a hawk, a peppercorn) can be good consideration. Payment by a third party in discharge of the debt can bar a later claim against the debtor. Composition with creditors is binding. And promissory estoppel, from Hughes v Metropolitan Railway and Central London Property Trust v High Trees House, can stop a person going back on a promise to accept less, where the other has relied on it. Estoppel suspends or restrains the right. It does not, by itself, hand over a new cause of action.

Economic pressure to renegotiate is dealt with as well. A promise extracted by illegitimate pressure may be voidable for economic duress. That is taken up in the duress chapter.