Your Cicero example is quite interesting. On one hand I too feel that it is not moral to break your word, but in the given example I would break my word and no

Your Cicero example is quite interesting. On one hand I too feel that it is not moral to break your word, but in the given example I would break my word and not give the gun back. In an effort to reconcile these positions, I would argue that my agreement with the original gun-owner contained the unstated understanding that it would only be returned if he was mentally fit. These sort of 'clauses' if you will are inherent in any agreement we make. It is understood that "I'll return the book to you on Tuesday." also contains the qualifier "assuming, of course, that: a meteor doesn't impact the earth, my car doesn't break down, the US doesn't enter nuclear war....etc." Still, I don't feel that agreeing to work for a company does not include the understanding that I'll work for them "as long as I don't get a better offer elsewhere." However, you may argue that it does, and I guess I'd have to give it to you in that case. It's just that...my own agreement wouldn't. By making this proposition I'm basically allowing anyone to break any contact by saying "well, my agreement contained this unstated understanding which lets me do ____". I think that most times the agreement is fully understood between both parties though. There are definitely examples where the line gets fuzzy though, which is why it's so important to communicate so that everyone is on the same page.