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If the fool would persist in his folly he would become wise.
'The fool doth think he is wise, but the wise man knows himself to be a fool.'
Young men think old men are fools; but old men know young men are fools.
Attribution
Quote text and notes from Wikiquote: Michael A. Stackpole (page history), available under CC BY-SA 4.0. Source quality and labels are our own summary of what Wikiquote records.