Related:

• A pointy head is the sign of a sharp mind.
• from the ancient Greek: Oxus = "sharp", Moros = "dull" -- Oxymoro
• A quiet tongue shows a wise head.
• A sharp tongue is the only edged instrument that grows keener with constant use. IRVING
• Be slow of tongue and quick of mind. CERVANTES
• I really would not be so bothered by people who speak out what they think, if before they spoke out, they actually did think.
  This is one of the main problems with a democracy....
• The narrower the mind, the broader the tongue. -- Confucius Say
• As sharp as a marble / bowling ball / beachball / pin head / bowl
• A sharp tongue is the only edged tool that grows keener with constant use.
  Washington Irving ['The Sketch Book', 1820]...