Why do people dig in their heels and adamantly refuse to admit they're wrong, even when the evidence is clearly against them? Why do people devote far more resources to fighting a battle than they can possibly recover, even if they win? How can both parties to a dispute be so certain of winning? Why do people resist changes that will make them better off? Who do people act contrary to their own beliefs? Why do people often find it so hard to figure out what they want? The answer to all these questions is that our minds are out of date. They evolved to resolve disputes among inhabitants of simple, stable, and homogeneous communities. The complex, diverse, and dynamic society we live in presents challenges that the mental tools we inherited from our ancestors are ill prepared to handle. You can learn how to overcome these challenges. Step one is learning to recognize when your mind is steering you in the wrong direction. Step two is learning how to get yourself back on track--and help others do the same.