If it be said that it is of the essence of a promise to be communicated, whether it goes through the stage of offer or not, meaning by communicated brought to the actual knowledge of the promisee, the law is believed to be otherwise. A covenant is binding when it is delivered and accepted, whether it is read or not. On the same principle, it is believed that, whenever the obligation is to be entered into by a tangible sign, as, in the case supposed, by letter containing the return promise, and the consideration for and assent to the promise are already given, the only question is when the tangible sign is sufficiently put into the power of the promisee. I cannot believe that, if the letter had been delivered to the promisee and was then snatched from his hands before he had read it, there would be no contract. /1/ If I am right, it appears of little importance whether the post-office be regarded as agent or bailee for the offerer, or as a mere box to which he has access. The offeree, when he drops the letter containing the counter-promise into the letter-box, does an overt act, which by general understanding renounces control over the letter, and puts it into a third hand for the benefit of the offerer, with liberty to the latter at any moment thereafter to take it. The principles governing revocation are wholly different. One to whom an offer is made has a right to assume that it remains open according to its terms until he has actual [307] notice to the contrary. The effect of the communication must be destroyed by a counter communication. But the making of a contract does not depend on the state of the parties' minds, it depends on their overt acts. When the sign of the counter promise is a tangible object, the contract is completed when the dominion over that object changes. [308] LECTURE IX. -- CONTRACT.--III. VOID AND VOIDABLE. THE elements of fact necessary to call a contract into existence, and the legal consequences of a contract when formed, have been discussed. It remains to consider successively the cases in which a contract is said to be void, and those in which it is said to be voidable,--in which, that is, a contract fails to be made when it seems to have been, or, having been made, can be rescinded by one side or the other, and treated as if it had never been. I take up the former class of cases first. When a contract fails to be made, although the usual forms have been gone through with, the ground of failure is commonly said to be mistake, misrepresentation, or fraud. But I shall try to show that these are merely dramatic circumstances, and that the true ground is the absence of one or more of the primary elements, which have been shown, or are seen at once, to be necessary to the existence of a contract.