Every year, about a month before Christmas, my sister, my mother and I sit down at the kitchen table (headquarters in an Italian family) and plan Christmas Eve dinner. Every year, my sister counts the number of fish I’m serving. (Seven are required to make Christmas Eve one of the hap happiest evenings of all.)

One year, I tried to pull a fast one. I was planning on making just six fish. My sister, otherwise known as our culinary commander, counted the number on her fingers. A brief eruption ensued. “You only have six fish,” she accused. “Well,” I stammered lamely, “what’s the difference? Six fish vs. seven? Who’s gonna care?”