Why is the Mona Lisa the most famous painting in the world? Why did Facebook succeed when other social networking sites failed? Did the surge in Iraq really lead to less violence? And does higher pay incentivize people to work harder? If you think the answers to these questions are a matter of common sense, think again. As sociologist and network science pioneer Duncan Watts explains in this provocative book, the explanations that we give for the outcomes that we observe in life-explanations that seem obvious once we know the answer-are less useful than they seem. Watts shows how commonsense reasoning and history conspire to mislead us into thinking that we understand more about the world of human behavior than we do; and in turn, why attempts to predict, manage, or manipulate social and economic systems so often go awry. Only by understanding how and when common sense fails can we improve how we plan for the future, as well as understand the present-an argument that has important implications in politics, business, marketing, and even everyday life.