HKB
whoever uses them is immediately bound by his interest to execute his engagements, and must never expect to be trusted any more, if he refuse to perform what he promised.
Nor is that knowledge, which is requisite to make mankind sensible of this interest in the institution and observance of promises, to be esteemed superior to the capacity of human nature, however savage and uncultivated. There needs but a very little practice of the world, to make us perceive all these consequences and advantages. The shortest experience of society discovers them to every mortal; and when each individual perceives the same sense of interest in all his fellows, he immediately performs his part of any contract, as being assured, that they will not be wanting in theirs. All of them, by concert, enter into a scheme of actions, calculated for common benefit, and agree to be true to their word; nor is there any thing requisite to form this concert or convention, but that every one have a sense of interest in the faithful fulfilling of engagements, and express that sense to other members of the society. This immediately causes that interest to operate upon them; and interest is the first obligation to the performance of promises.
Afterwards a sentiment of morals concurs with interest, and becomes a new obligation upon mankind. This sentiment of morality, in the performance of promises, arises from the same principles as that in the abstinence from the property of others. Public interest, education, and the artifices of politicians, have the same effect in both cases. The difficulties, that occur to us, in supposing a moral obligation to attend promises, we either surmount or elude. For instance; the expression of a resolution is not commonly supposed to be obligatory; and we cannot readily conceive how the making use of a certain form of words should be able to cause any material difference. Here, therefore, we feign a new act of the mind, which we call the willing an obligation; and on this we suppose the morality to depend. But we have proved already, that there is no such act of the mind, and consequently that promises impose no natural obligation.