Man has almost constant occasion for the help of his
brethren, and it is in vain for him to expect it from their benevolence only. He will be
more likely to prevail if he can interest their self-love in his favor, and show them that
it is for their own advantage to do for him what he requires of them. Whoever offers to
another a bargain of any kind, proposes to do this. Give me that which I want, and you
shall have this which you want, is the meaning of every such offer; and it is in this
manner that we obtain from one another the far greater art of those good offices which we
stand in need of. It is not from the benevolence of the butcher, the brewer, or the baker
that we expect our dinner, but from their regard to their own interest.