Book excerpt: What is the basis for intolerance? This book addresses that question by developing a universal theory about what causes intolerance of difference in general, which includes racism, political intolerance (e.g. restriction of free speech), moral intolerance (e.g. homophobia, supporting censorship, opposing abortion) 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.