SECT.  V OF THE OBLIGATION OF PROMISES

That the rule of morality, which enjoins the performance of promises, is not natural, will sufficiently appear from these two propositions, which I proceed to prove, viz, that a promise would not be intelligible, before human conventions had established it; and that even if it were intelligible, it would not be attended with any moral obligation.

I say, first, that a promise is not intelligible naturally, nor antecedent to human conventions; and that a man, unacquainted with society, could never enter into any engagements with another, even though they could perceive each other’s thoughts by intuition.  If promises be natural and intelligible, there must be some act of the mind attending these words, I promise; and on this act of the mind must the obligation depend.  Let us, therefore, run over all the faculties of the soul, and see which of them is exerted in our promises.

The act of the mind, exprest by a promise, is not a resolution to perform any thing:  For that alone never imposes any obligation.  Nor is it a desire of such a performance:  For we may bind ourselves without such a desire, or even with an aversion, declared and avowed.  Neither is it the willing of that action, which we promise to perform:  For a promise always regards some future time, and the will has an influence only on present actions.  It follows, therefore, that since the act of the mind, which enters into a promise, and produces its obligation, is neither the resolving, desiring, nor willing any particular performance, it must necessarily be the willing of that obligation, which arises from the promise.  Nor is this only a conclusion of philosophy; but is entirely conformable to our common ways of thinking and of expressing ourselves, when we say that we are bound by our own consent, and that the obligation arises from our mere will and pleasure.  The only question then is, whether there be not a manifest absurdity in supposing this act of the mind, and such an absurdity as no man coued fall into, whose ideas are not confounded with prejudice and the fallacious use of language.

All morality depends upon our sentiments; and when any action, or quality of the mind, pleases us after a certain manner, we say it is virtuous; and when the neglect, or nonperformance of it, displeases us after a like manner, we say that we lie under an obligation to perform it.  A change of the obligation supposes a change of the sentiment; and a creation of a new obligation supposes some new sentiment to arise.  But it is certain we can naturally no more change our own sentiments, than the motions of the heavens; nor by a single act of our will, that is, by a promise, render any action agreeable or disagreeable, moral or immoral; which, without that act, would have produced contrary impressions, or have been endowed with different qualities.  It would be absurd, therefore, to will any new obligation, that is, any new sentiment of pain or pleasure; nor is it possible, that men coued naturally fall into so gross an absurdity.  A promise, therefore, is naturally something altogether unintelligible, nor is there any act of the mind belonging to it.