It is customarily said that mutual assent is essential to the formation of simple contracts, but it should further be stated that the mutual assent must be expressed by one party to the other, and except as so expressed is unimportant. In some branches of the law, especially in the criminal law, a person's secret, intent is important, but in the formation of contracts it was long ago settled that secret intent was immaterial; only overt acts being considered in the determination of such mutual assent as that branch of the law requires.1 During the first half of the nineteenth century there are many expressions which seem to indicate the contrary, but that the fundamental basis of contract in the common law is reliance on an outward act (that is a promise) is shown by the early development of the law of consideration as compared with that of mutual assent. Courts of equity indeed have not shown the same indifference to the undisclosed intent of the parties, as have courts of law; but equity makes its views effective not by denying or altering the rules of law governing the formation of contracts but by subsequently reforming or rescinding legally valid contracts in cases coming within its own rules. Not only must assent to a contract be expressed by overt acts, but promises in contracts must be made by an expression of agreement moving from the promisor to the promisee. The assent of the promisee to a unilateral contract may be indicated by an act requested by the promisor, but of which he has no knowledge, and is not likely to acquire knowledge unless he takes steps to inform himself; 2 but a promise necessarily implies either communication from the promisor to the promisee, or at least some action which will normally indicate to the promisee the intent of the promisor.

1 "It is trite learning that the thought of man is not triable, for the devil himself knows not the thought of man." Brian in Y. B., 17 Edw. IV, 1. In O'Donnell v. Clinton, 146 Man. 461, 463, 14 N. E. 747, the court said: "Intention is immaterial till it manifests itself in act. If a man intends to buy, and says so to the intended seller, and he intends to sell, and says so to the intended buyer, there is a contract of sale; and so there would be if neither had the intention. If there is a contract of sale, and the seller intends to appropriate a particular chattel in fulfilment of it, and the buyer intends to accept, and accepts, the property vests in him; and so it would had there been no such intention. If the buyer refuses, and the chattel corresponds with the contract, the vendor has a right of action, not because of his intention, but of his offer. An intention not communicated to the buyer is immaterial. Telling it to an indifferent person is no more than though he had noted it in his memorandum book, which is no more than though it existed in his own mind." See also Browne v. Hare, 3 H. & N. 484, 495. Williams v. Bur-dick, 63 Or. 41, 128 Pac. 603. 2 See infra, Sec.Sec. 68, 69, 71.