People like to hear themselves talk. People like to be thought of as witty and wise. Some people project the idea that they know everything or most everything...and want to share what they know with you.
What I think about when I read Voltaire's quote is that we all have 2 ears and one mouth so we should listen twice as much as we speak.
I also think about what I was taught when I was a young man: when you encounter someone who has all the answers, walk away. Adding to it, I learned that the time I think I have a
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Perhaps Voltaire was talking about being a thoughtful person. Thoughtful people ask great questions, not just a lot of them. The questions they ask show they're thinking and can often make you stop and question your own thought processes or your own views of a problem. Great, thoughtful questions can cut through all the clutter and get to the meat of an issue. They add to the dialog instead of turning attention away from it like poor questions can do.
Do you ask many questions? What kind of questions do you ask? Do they add to the discussion at hand?