Gratitude and Revenge.—The reason the powerful man is grateful is this. His benefactor has, through his benefaction, invaded the domain of the powerful man and established himself on an equal footing: the powerful man in turn invades the domain of the benefactor and gets satisfaction through the act of gratitude. It is a mild form of revenge. By not obtaining the satisfaction of gratitude the powerful would have shown himself powerless and have ranked as such thenceforward. Hence every society of the good, that is to say, of the powerful originally, places gratitude among the first of duties.—Swift has added the dictum that man is grateful in the same degree that he is revengeful.