Does smoking cause lung cancer? How could you ever know? The second in a three-part series on causality, I’m joined by Dr. Shoshana Herzig to discuss how Austin Bradford Hill and Richard Doll set out to try and answer this question -- and along the way revolutionized the way we think about what causes disease. In this episode, we’ll talk about the first double-blinded randomized controlled trial, the long shadow of tuberculosis, and why epidemiology is beautiful.