ABSTRACT
In a bilateral contract, each party is both a promisor and a promisee. For example, suppose Alice agrees to sell a book to Bertha for £10: Alice is the promisor of the books and the promisee of £10. Conversely, B is the promisor of the £10 and the promisee of the books. Therefore, either Alice or Bertha may sue on the contract, but no one else. In a unilateral contract, there is only one promisee. That person must show that consideration, in the form of an act or forbearance, has moved from him to the defendant.
