In the Context of English Law

Here, English contract doctrine distinguishes between bilateral and unilateral contracts. A bilateral contract gives rise to obligations on both sides. Thus in a contract of sale, the seller has an obligation to transfer title in the thing sold to the buyer, whilst the buyer has an obligation to pay the price. A unilateral contract, by contrast, gives rise to obligations on one side only. Thus "I will give you £100 if you run a marathon" gives rise to a legal duty on the maker of the statement (the promisor) to pay the money if the race is run, whilst the person to whom the statement is made (the promisee) is under no obligation to run in the first place.

a. A promise

In the context of English law, a reference to a promise here may be seen as misleading. It is often (rightly) stated that English law will not give effect to a mere promise and that an agreement, or meeting of minds, is required. In fact, this is simply a way of distinguishing between two types of promise, namely those which do and don't give rise to a legal duty. Thus, a promise to meet one's other half for dinner at 7pm gives rise to no legal obligation - it is a "mere" promise - whereas a promise to sell someone a car for £5000 gives rise to legal obligation.

b. A legal duty arising from that promise

Here, English contract doctrine distinguishes between bilateral and unilateral contracts. A bilateral contract gives rise to obligations on both sides. Thus in a contract of sale, the seller has an obligation to transfer title in the thing sold to the buyer, whilst the buyer has an obligation to pay the price. A unilateral contract, by contrast, gives rise to obligations on one side only. Thus "I will give you £100 if you run a marathon" gives rise to a legal duty on the maker of the statement (the promisor) to pay the money if the race is run, whilst the person to whom the statement is made (the promisee) is under no obligation to run in the first place.

c. A remedy for breach of that duty

In considering the development of remedies, a fundamental distinction in English law between common law (often just abbreviated to law) and equity must be understood. For much of its history, England had two separate systems of law working side by side, each of which had different rules. One, administered by the courts of common pleas