Butler asks why, if free trade is such an eminently rational policy, protectionism has been rife throughout human history. The answer, he says, lies in our deep evolutionary psychology. For example, we have evolved with a strong bias toward our own group and a disposition to raise defences (including trade barriers) against others. We fear, and remember, losses more than gains because that aids our survival: so we dread the potential losses from foreign competition more than we welcome the gains. Likewise, rational arguments (such as the long-term benefits of trade) move us less than emotional appeals (such as the distress of losing a job). We can counter these biases says Butler, only by understanding and addressing them, and presenting the human case for free trade.