Current public debates, not just about climate change and corona restrictions, seem to become increasingly ‘irrational’. Why does rationality seem to be in decline? Pinker takes the reader on a tour deforce through the different ingredients of rational thinking. We learn about the foundations of logic and probability, how to process evidence to update our beliefs, and how to make good decisions based on our knowledge. In these parts of the book, Pinker covers a lot of ground, but manages to present sometimes complex material in an accessible way. Each chapter uses intuitive examples and illustrations that make the book an entertaining read, despite material that is usually covered in statistical textbooks (which are probably the opposite of what we call “entertaining reads”). How does all this help us understand irrationality in current debates? In Chapter 10 Pinker finally turns to this question – the ‘chapter most of you have been waiting for’. He discusses a number of explanations such as motivated reasoning or the ‘myside bias’, where reality and truth become negotiable and adjustable depending on the political position they originate from. These, and several others, are common fallacies in human thinking, and Pinker presents a number of scientific findings attesting to this. Not surprisingly for a book with a psychological focus, however, most of the research presented here takes an individualist perspective, drawing on psychological experiments or surveys. Political scientists will therefore ask how this affects democratic debates in the aggregate, or even democracy as a whole. These are important questions, and as Pinker’s book shows, there is some real cause for concern – but also a need for more political science research.