An offer for a unilateral contract generally requires an act on the part of the offeree to make a binding contract. This act is consideration for the promise contained in the offer and doing it with intent to accept without more will create a contract.1 But an expression of mutual assent is necessary to the formation of simple contracts as well as consideration, and the fact that the same act must also be a manifestation of acceptance by the offeree is not always observed. On the other hand, an offer for a bilateral contract requires a promise from the offeree in order that there may be a binding contract. This promise may be inferred from any words of the offeree indicating assent to the proposed bargain and, generally, must be found by interpretation of language which does not in terms state a promise. That is, the offeree will say or write "I accept your proposition," or words to that effect, instead of saying "I promise to do what you request." 2 So that in bilateral contracts the fact that the offeree's acceptance is also a promise, furnishing the requisite consideration, is not always observed.
1 See infra, Sec. 68.