The death at age 78 of our oldest friend, coming as it does in a season when so many are thinking of generational change, is a moment to tell the story of what we like to call the world’s most powerful man. That’s how, during the early 1980s, we described Jim Rosenstein. If he were alive today, he would dispute this story — and so would anyone else who knew him. They’d insist that we have too lively an imagination.