Suppose you borrowed $10 from Tom and $10 from Bob. On your way to repaying them you are robbed of everything but the $10 you had hidden in your shirt pocket. By no fault of your own, you now face the following paradoxical dilemma:

(1) You are obligated to repay Tom and Bob.
(2) If you pay Tom you cannot repay Bob.
(3) If you repay Bob you cannot repay Tom.
(4) You cannot honor all your obligations: in the circumstances this is impossible for you. (By (1)-(3).)
(5) You are (morally) required to honor all your obligations.
(6) You are not (morally) required to do something you cannot possibly do (ultra posse nemo obligatur).

— Nicholas Rescher, Paradoxes, 2001