For over two thousand years, scientific progress has relied on different methods of establishing fact from fiction. From the medieval Islamic world ot the recent pandemic, the reasoning went: achieve logical perfection, and you would be rewarded with ultimate, universal truth. But there is far more to proof than axioms, theories and laws: when demonstrating that a new medical treatment works, persuading a jury of someone''s guilt, or deciding whether you trust a self-driving car or a financial transaction, the weighing up of evidence is far from simple. Bestselling author, statistician and epidemiologist Adam Kucharski ranges across science, politics, philosophy and economics, to explore how truth emerges - and why it falters.