Epops: You're mistaken: men of sense often learn from their enemies. Prudence is the best safeguard. This principle cannot be learned from a friend, … - Aristophanes

It is from their foes, not their friends, that cities learn the lesson of building high walls

Men of sense often learn from their enemies. It is from their foes, 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.

... men of sense often learn from their enemies. Prudence is the best safeguard. This principle cannot be learned from a friend, but an enemy extorts it immediately. It is from their foes, 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.

Epops: The wise can often profit by the lessons of a foe, for caution is the mother of safety. It is just such a thing as one will not learn from a friend and which an enemy compels you to know. To begin with, it's the foe and not the friend that taught cities to build high walls, to equip long vessels of war; and it's this knowledge that protects our children, our slaves and our wealth. Leader of the Chorus [leader]: Well then, I agree, let us first hear them, for that is best; one can even learn something in an enemy's school. (tr. O'Neill 1938, Perseus)

Æschylus: High thoughts must have high language. (rewritten and embellished tr. Fitts 1955, p. 108)

— ¿De verdad crees en los dioses? — Yo sí. — ¿En qué te basas? — En que me aborrecen. ¿No es un indicio verosímil?