What are the root causes of intolerance? This book addresses that question by developing a universal theory of what determines intolerance of difference in general, which includes racism, political intolerance, moral intolerance and punitiveness. It demonstrates that all these seemingly disparate attitudes are principally caused by just two factors: individuals' innate psychological predispositions to intolerance ("authoritarianism") interacting with changing conditions of societal threat. The threatening conditions, particularly resonant in the present political climate, that exacerbate authoritarian attitudes include, most critically, great dissension in public opinion and general loss of confidence in political leaders. Using purpose-built experimental manipulations, cross-national survey data and in-depth personal interviews with extreme authoritarians and libertarians, the book shows that this simple model provides the most complete account of political conflict across the ostensibly distinct domains of race and immigration, civil liberties, morality, crime and punishment, and of when and why those battles will be most heated.