Thirty years ago, I was hiking alone on a section of the Appalachian Trail known as "Rocky Top" when I encountered two stocky young men. The thought occurred to me that they could easily kill me, toss my body in the brush, and get away scot-free. Whether the thought occurred to either of them, I will never know. I passed them by with a brief nod and moved on quickly to the turn-off leading to my parked car. But I remained troubled, and remain so today, by the fact that I had been so completely at risk. I had been...