“Factfulness is … recognizing that a single perspective can limit your imagination, and remembering that it is better to look at problems from many angles to get a more accurate understanding and find practical solutions. To control the single perspective instinct, get a toolbox, not a hammer. • Test your ideas. Don’t only collect examples that show how excellent your favorite ideas are. Have people who disagree with you test your ideas and find their weaknesses. • Limited expertise. Don’t claim expertise beyond your field: be humble about what you don’t know. Be aware too of the limits of the expertise of others. • Hammers and nails. If you are good with a tool, you may want to use it too often. If you have analyzed a problem in depth, you can end up exaggerating the importance of that problem or of your solution. Remember that no one tool is good for everything. If your favorite idea is a hammer, look for colleagues with screwdrivers, wrenches, and tape measures. Be open to ideas from other fields. • Numbers, but not only numbers. The world cannot be understood without numbers, and it cannot be understood with numbers alone. Love numbers for what they tell you about real lives. • Beware of simple ideas and simple solutions. History is full of visionaries who used simple utopian visions to justify terrible actions. Welcome complexity. Combine ideas. Compromise.”