6. A promise is the communication by a person of an intention and willingness to be bound to do or to forbear from doing something at the request or for the use of another, when, but not before, that declaration has become binding by its acceptance by the promisee so as to create an obligation.26 A promissory expression before acceptance is merely an offer of a promise.
We are in the habit of considering as the essential feature of contract a promise by one or more parties to another or others to do or to forbear from doing certain specified acts; and many of the books use the term "promise," rather than "agreement," to define contract. "In an agreement as the source of a legal contract," it is said, "the matter intended and agreed imports that the one party shall be bound to the other in some act or performance, which the latter shall have a legal right to enforce." The signification of an intention to do some act, or observe some particular course of conduct, made by the one party to the other, and accepted by him, for the purpose of creating a right to its accomplishment, is called a promise.27
The term "promise" is used to signify a binding promise, as opposed to a mere offer of a promise. A promissory expression amounting to an offer of a promise does not become a promise until it becomes binding by its acceptance by the person to whom it is made. Before it is accepted it is a mere offer of a promise, called in the civil law a "pollicitation."28 It must also be noted that it is not every statement of intention that will amount to an offer of a promise which by acceptance will be turned into a promise. An offer differs from a mere statement of intention in that it imports a willingness to be bound to the party to whom it is made. If a person says to another, "I intend to sell my horse if I can get $100 for it," there is no offer that can be turned into an agreement, but merely a declaration of intention. There is no declaration of willingness to be bound. If, however, he says, "I will sell you my horse if you will give me $100 for it," there is an offer, and, if it is accepted, there is a contract, consisting of mutual binding promises to deliver the horse on the one side, and to accept and pay for it on the other.
26 Anson, Cont. (4th Ed.) 4; Pol. Cont. 1.
27 Leake, Cont 13. 28 See post, p. 20.
Looking at a contract, then, in the light of a promise, we may say that there are three stages necessary to the making of that sort of agreement which results in a contract: (1) There must be an offer; (2) there must be an acceptance of the offer, resulting in a promise; and (3) the law must attach a binding force to the promise, so as to invest it with the character of an obligation.
The promise results from the agreement of the parties, and necessarily results from every agreement which directly contemplates and creates an obligation. The agreement makes the contract, and the promise is merely a feature of the contract.