In the early 1970s, when a friend and I were newly hatched social psychologists, we decided to write a book on happiness. The head of an eminent Boston publishing house took pity on us and, over lunch, explained the facts of life. ‘No one wants to read a book on happiness’, he said kindly. ‘Happy people don’t; why in the world would they want to? They are already happy. Unhappy people don’t want to, either. Why in the world would they want to read about happy people when they are feeling sullen and miserable? Moreover, it’s faintly embarrassing to be seen on a bus or park bench reading a book on happiness. It’s like being caught reading a book on paedophilia. A passer-by will question your motives.’ And so my friend and I went our separate ways; he to write a book on loneliness, and I, a book on anger.