"Better to remain silent and appear a fool, than to open your mouth and remove all doubt"

  My family has dinner together almost every night and we normally talk about our days.  My dad is a phys. ed. teacher and right now he teaches middle school boys.  He doesn't always have the brightest of students in his classes, which means very entertaining stories for us to listen to at the dinner table.  This is something that my dad used to say to my sister and I when he was talking about some of those students that weren't necesarily using theirs brains to the best of their ability.  My dad can be extremly sarcastic sometimes and has almost no patience for you if you aren't going to listen to him.  This generally ammounts to him making some sarcastic commment that sometimes the student doesn't understand, but would try to respond to as if his comment was literal and end up looking like a "fool".