But, _secondly_, if there was any act of the mind belonging to it, it could not _naturally_ produce any obligation. This appears evidently from the foregoing reasoning. A promise creates a new obligation. A new obligation supposes new sentiments to arise. The will never creates new sentiments. There could not naturally, therefore, arise any obligation from a promise, even supposing the mind could fall into the absurdity of willing that obligation. The same truth may be proved still more evidently by that reasoning which proved justice in general to be an artificial virtue. No action can be required of us as our duty, unless there be implanted in human nature some actuating passion or motive capable of producing the action. This motive cannot be the sense of duty. A sense of duty supposes an antecedent obligation; and where an action is not required by any natural passion, it cannot be required by any natural obligation; since it may be omitted without proving any defect or imperfection in the mind and temper, and consequently without any vice. Now, 'tis evident we have no motive leading us to the performance of promises, distinct from a sense of duty. If we thought that promises had no moral obligation, we never should feel any inclination to observe them. This is not the case with the natural virtues. Though there was no obligation to relieve the miserable, our humanity would lead us to it; and when we omit that duty, the immorality of the omission arises from its being a proof that we want the natural sentiments of humanity. A father knows it to be his duty to take care of his children, but he has also a natural inclination to it. And if no human creature had that inclination, no one could lie under any such obligation. But as there is naturally no inclination to observe promises distinct from a sense of their obligation, it follows, that fidelity is no natural virtue, and that promises have no force antecedent to human conventions. If any one dissent from this, he must give a regular proof of these two propositions, viz. _that there is a peculiar act of the mind annexed to promises_; and _that consequent to this act of the mind, there arises an inclination to perform, distinct from a sense of duty_. I presume that it is impossible to prove either of these two points; and therefore I venture to conclude, that promises are human inventions, founded on the necessities and interests of society.