Post-factual politics has united scientists and civil society in a public defence of truth, however, the battle may already have been lost to a binarity of facts and emotions. Analysing and comparing scientists’ protests against the Trump presidency with famous scientific controversies in modern medicine, this innovative book redefines truth as a negotiation in public discourse between the interplay of values, beliefs and facts. It shows that in order to understand post-factual politics we must unveil emotion’s role in knowledge-making.