Where there is no such commission, if another, to whom the promise was not directly made, accepts it with the consent of the promiser, the promise will be so far binding, that the promiser will not be at liberty to revoke it, before the person, in whose favour it was made has ratified, and afterwards chosen to release the engagement. Yet, in the mean time, the accepter cannot release it, as having derived no peculiar right from it himself, but only been used as an instrument in promoting the kind intentions and good faith of the promiser. The promiser therefore himself, by revoking it, is not doing violence to the perfect right of another, but only acting in contradiction his own good faith. XIX. From what has been said before, it is easy to conceive what opinion ought to be entertained of a burdensome condition annexed to a promise. For it may be annexed at any time, till a promise has been completed by acceptance, or an irrevocable pledge to fulfil it has been given. But the condition of a burden annexed to a favour intended to be conferred upon a third person, through the medium of any one, may be revoked before the person has confirmed it by his acceptance. On this point there is great difference of opinion. But upon impartial consideration the natural equity of any case may be easily seen without any great length of arguments. XX. XXI. XXII. Another point of discussion relates to the validity of an erroneous promise, when the person, who made it, upon being apprised of his error is willing to adhere to his engagement. And the same inquiry applies to promises, which, arising out of fear or any other such motive, are prohibited by the civil law. What, it may be asked, will become of these promises, if that fear, or that motive has been removed? To confirm such obligations, some think an internal consent of the mind alone in conjunction with some previous external act is sufficient. Others disapprove of this opinion, because they do not admit that an external act is a real sign of a subsequent intention. Therefore they require an express repetition of the promise and acceptance. Between these two opinions, the truth is most likely to be found. There may be an external act expressive of a promise, though unaccompanied with words; where one party's accepting and retaining a gift, and the other's relinquishing his right in it are sufficient to constitute a full consent. To prevent civil laws from being confounded with natural justice, we must not omit noticing, in this place, that promises though founded in no EXPRESS motive, are not, any more than gifts, void by the law of nature.