How does a zipper work? Rate your understanding on a scale from 0 (no clue) to 10 (easy-peasy). Write the number down. Now sketch out on a piece of paper how a zipper actually works. Add a brief description, as though you were trying to explain it very precisely to someone who'd never seen a zipper before. Give yourself a couple of minutes. Finished? Now reassess your understanding of zippers on the same scale.

     Leonid Rozenblit and Frank Keil, researchers at Yale University, confronted hundreds of people with equally simple questions. How does a toilet work? How does a battery work? The results were always the same: we think we understand these things reasonably well until we're forced to explain them. Only then do we appreciate how many gaps there are in our knowledge. You're probably similar. You were convinced you understood more than you actually did. That's the knowledge illusion.
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     In sum: think independently, don't be too faithful to the party line, and above all give dogmas a wide berth. The quicker you understand that you don't understand the world, the better you'll understand the world

The Art of the Good Life / Rolf Dobelli