Whether by the law of nature a right arises from a promise

The order of our work has brought us to the obligation which arises from promises. [Some persons maintain] the opinion that, according to the law of nature, as well as the law of nations, no obligation is created by those agreements which do not contain an exchange of considerations; that nevertheless, such agreements are honourably carried out if only the matter is of such a nature that it would have been honourable and consistent with some other virtue to fulfil them even without the promise.

[In support of this view, the argument is advanced] that the individual who rashly believes a person that makes a promise without any reason for it is not less at fault than the person who has made a worthless promise; then, that the fortunes of all would be greatly imperilled if men should be bound by a mere promise, which proceeds often from the love of display rather than from a purpose, or from a purpose, indeed, but a trivial and ill-considered purpose; finally, that it is just to leave something to the honesty of each person.