Book 4.35

When I promise to bestow a benefit, I promise it, unless something occurs which makes it my duty not to do so. What if, for example, my country orders me to give to her what I had promised to my friend? or if a law be passed forbidding any one to do what I had promised to do for him? Suppose that I have promised you my daughter in marriage, that then you turn out to be a foreigner, and that I have no right of intermarriage with foreigners; in this case, the law, by which I am forbidden to fulfil my promise, forms my defence. I shall be treacherous, and hear myself blamed for inconsistency, only if I do not fulfil, my promise when all conditions remain the same as when I made it; otherwise, any change makes me free to reconsider the entire case, and absolves me from my promise. I may have promised to plead a cause; afterwards it appears that this cause is designed to form a precedent for an attack upon my father. I may have promised to leave my country, and travel abroad; then news comes that the road is beset with robbers. I was going to an appointment at some particular place; but my son's illness, or my wife's confinement, prevented me. All conditions must be the same as they were when I made the promise, if you mean to hold me bound in honour to fulfil it. Now what greater change can take place than that I should discover you to be a bad and ungrateful man? I shall refuse to an unworthy man that which I had intended to give him supposing him to be worthy, and I shall also have reason to be angry with him for the trick which he has put upon me.