For generations, the cup of coffee sat at the bedside of cardiac patients as a quiet suspect — blamed, avoided, and mourned. Now, researchers from UC San Francisco and the University of Adelaide have turned that long-held caution on its head, finding that daily coffee consumption may reduce the risk of atrial fibrillation by nearly 40 percent. In a world where medical certainty so often proves provisional, this study invites us to reconsider not just a beverage, but the humility required of all received wisdom.