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Homér 217
Ancient Greek epic poet, author of the Iliad and the OdysseyRelated quotes
Notre Dame head coach Charlie Weis, quoted at Ringer 23.com (undated)

“fool me once, shame on you. fool me twice, shame on me.”
Source: Count Your Blessings

“Wise men learn more from fools than fools from the wise.”
Plutarch's Life of Cato
Variant: Wise men profit more from fools than fools from wise men; for the wise men shun the mistakes of fools, but fools do not imitate the successes of the wise.

“Fools learn wisdom through misfortune.”
Source Book in Ancient Philosophy (1907), The Golden Sayings of Democritus