You're mistaken; men of sense often learn much from their enemies. Prudence is the best safeguard. This principle cannot be learnt from a friend: but an enemy extorts it immediately. It is from their foes and not their friends, that cities learn the lesson of building high walls and ships of war. And this lesson saves their children, their homes, and their properties.
AristophanesShall I crack any of those old jokes, master, At which the audience never fail to laugh?
Aristophanes