Grist: Sometimes being a parent feels like a tedious vigil against death. The other day, when I asked my 4-year-old not to show me her somersault skills at the top of an unusually steep flight of stairs, she looked at me with wounded confusion.
"Why?" she asked.
"Well," I said, "because there`s a small chance you might fall, and you would land on the stairs, so you would keep falling, faster and faster, and every time you hit the ground you might break a bone, and maybe the broken end of your arm...