A bit of a moral dilemma I thought up: There was once a strong and righteous paladin who had sworn a holy oath to always aid the innocent and defenseless and to safeguard them from evil. One day he rides by a tower and hears a woman cry for help from the topmost window. She claims to be an innocent maiden who has been imprisoned against her will by an evil knight, who refuses to let her out unless she agrees to marry him. The door to the tower is locked by a magic seal, and the key will only turn for the knight who locked it, or one who has bested him in combat. She pleads to the paladin to kill the knight and release her. Moments later the knight himself appears. He tells the paladin that it is true the tower can only be unlocked by himself or whoever defeats him, but claims everything else the maiden said is a lie. According to the knight, the woman is really a terrible monster in disguise; a demon that was sealed in the tower as no man could slay it. He stresses that the door to the tower must never be opened. The paladin cannot tell who is lying and who is telling the truth. Whenever one makes a claim, the other claims the opposite. If the maiden is telling the truth, his oath demands that he aid her. But if the knight is telling the truth, the same oath demands that he ensure the tower remains locked. What should he do?