It comes as no surprise to learn from a study published this week that, although Britons are twice as rich as they were in 1987, they are no happier.

The lack of relationship between wealth and happiness has long been common knowledge, and the knowledge itself has long been a source of happiness to moralisers who like the fact that money is not life's answer.

There are, though, two confusions involved in the idea that anything significant can be discovered by looking for a correlation between wealth and happiness. One concerns the nature of happiness, the other the nature of wealth.