The introductory chapter explains the puzzle of autocratic reverse waves that un-do liberal democratic progress. As an explanation, the book highlights the reactionary backlash to revolutionary challenges. As left-wingers inspired by a "successful" revolution try to spread radical change across countries, fearful right-wingers try with all means to block these efforts. Radical diffusion thus provokes reactionary counter-diffusion. Both the hopes of the left and the fears of the right are exaggerated, however, because cognitive heuristics that humans commonly employ suggest distorted, problematic inferences. With this argument, the book contributes to the debate about the nature of rationality, which recent theories of democratic breakdown have renewed. To substantiate its arguments, the book uses comparative-historical analysis based on a wealth of primary documents and secondary literature. A summary of the following chapters concludes this introduction