In the early 2000s, Clive Bates was one of Britain's foremost advocates against cigarette smoking and Big Tobacco. Today he is one of the world's foremost proponents of e-cigarettes as a way to help people quit smoking and reduce the harms caused by combustible cigarettes. There's no better teacher about tobacco harm reduction than Clive, which is why I pressed him on the toughest questions: Aren't the risks of e-cigarettes still unknown? Shouldn't we be concerned about people developing a lifelong addiction to vaping nicotine? [...]