I witnessed this firsthand at my weekly bridge game. My bridge partner, in her early forties and fully vaccinated, insisted that we play outside, in cold, damp weather. My opponent, in his sixties and also vaccinated, asked why we should suffer. She explained that the evidence was not yet established that indoor activities with vaccinated people were safe. The discussion got heated, and my friend later asked me if she was being unreasonable. I shrugged and said that we all have to do what makes us comfortable, but the evidence is encouraging that vaccinated people not only can’t transmit the virus but also face essentially no risk of severe illness. She nodded—and said that she’d play bridge inside when there was definitive evidence that it was completely safe. Such evidence may never come. Science is rarely that definitive.