The relentless American habit of optimism stirs our love-hate relationship with the US. The mindless “have a nice day” corporate smile on the face of an underpaid burger flipper is hideous to behold. But that can-do cast of mind also seems to power up the great engine of US inventiveness.

Barbara Ehrenreich, one of the sharpest US reporters and thinkers, has turned her laser analysis on the creed of positive thinking. Behind the smile she finds a national delusion that has become a cult of immense political significance. To outsiders the American dream is a puzzle. How does the United States delude itself that it is the classless land of opportunity when any league table or graph you choose to consult—I suggest The Spirit Level by Richard Wilkinson and Kate Pickett for examples (see Observations, BMJ 2009;338:b1293, doi:10.1136/bmj.b1293)—shows the US as not only the most unequal but the least socially mobile of all Western nations?

Ehrenreich has the answer: the power of positive thinking. Hyped up by motivational cheerleading in …