One afternoon twenty-odd years ago, a strange paranoid mood was upon me. As I walked down the aisles of a grocery store filling my shopping cart, I kept thinking, “Any one of these strangers I keep passing could, if he or she wanted, lunge at me with a knife, stab me in the chest, and kill me.” The possible bloodshed was extremely unlikely, I knew, but I became very uncomfortable each time someone walked by.
Back home, I told a roommate about my delusion. “That’s funny,” he said. “Sometimes I walk down the aisles thinking that I could kill any of these people if I wanted to.”