interest

I am led into this conjecture, by having remarked, that though love, friendship, esteem, and such like, have very powerful operations in the human mind, interest, however, is an ingredient seldom omitted by wise men, when they would work others to their own purposes. This is indeed a most excellent medicine, and, like Ward's pill, flies at once to the particular part of the body on which you desire to operate, whether it be the tongue, the hand, or any other member, where it scarce ever fails of immediately producing the desired effect.

-- Henry Fielding Tom Jones