In country after country, conspiracy theories and religious dogmas that once seemed to have been overtaken by enlightened thought are helping to loft authoritarian leaders into power. The effects are being felt by women, ethnic minorities, teachers, scientists, and students – and by the environment, the ultimate victim of climate change denial. We need clear thinking now more than ever. Christer Sturmark is a crusading secular humanist as well as a Swedish publisher and entrepreneur, and The Flame of Reason is his manifesto for a better world. It provides a set of simple tools for clear thinking in the face of populist dogmas, anti-science attitudes and pseudo-philosophy, and suggestions for how we can move towards a new enlightenment. In this interview, I speak to Christer Sturmark about the characteristics of knowledge and truth, why we are facing a crisis of reason, and the mental tools we all need to navigate our world.