Both sides of the relation between consideration and promise, and the conventional nature of that relation, may be illustrated by the case of the cask. Suppose that the [295] truckman is willing to carry the cask, and the owner to let him carry it, without any bargain, and that each knows the other's state of mind; but that the truckman, seeing his own advantage in the matter, says to the owner, "In consideration of your delivering me the cask, and letting me carry it, I promise to carry it," and that the owner thereupon delivers it. I suppose that the promise would be binding. The promise is offered in terms as the inducement for the delivery, and the delivery is made in terms as the inducement for the promise. It may be very probable that the delivery would have been made without a promise, and that the promise would have been made in gratuitous form if it had not been accepted upon consideration; but this is only a guess after all. The delivery need not have been made unless the owner chose, and having been made as the term of a bargain, the promisor cannot set up what might have happened to destroy the effect of what did happen. It would seem therefore that the same transaction in substance and spirit might be voluntary or obligatory, according to the form of words which the parties chose to employ for the purpose of affecting the legal consequences. If the foregoing principles be accepted, they will be seen to explain a doctrine which has given the courts some trouble to establish. I mean the doctrine that an executed consideration will not sustain a subsequent promise. It has been said, to be sure, that such a consideration was sufficient if preceded by a request. But the objections to the view are plain. If the request was of such a nature, and so put, as reasonably to imply that the other person was to have a reward, there was an express promise, although not put in words, and that promise was made at [296] the same time the consideration was given, and not afterwards. If, on the other hand, the words did not warrant the understanding that the service was to be paid for, the service was a gift, and a past gift can no more be a consideration than any other act of the promisee not induced by the promise.