I raised the pistol at my dead friend's double. It was blocking our path. I'd blow its head off too - then I thought of the paradox that might have created. Paradoxes, I was losing count. "You ... killed me?" it blurted. "Move aside or you die again." Motionless, it reminded me of the complications that would cause. Kill it now, blow its head off, and how could I then do the same in the future I'd run from? Staring at its headless double,...