Avoiding security cameras and cutting up your supermarket loyalty cards might, on the other hand, make you a modern paranoiac, of which these authors guess there are increasingly many. How do they know? Well, according to psychological studies, "around 15 to 20% of the population have frequent paranoid thoughts", far more than the 1% of people who have severe paranoia associated with psychosis. Also, lots of people believe in internet conspiracy theories; and folk in general are bad at comparing risks being more afraid, for example, of paedophiles than they are of road traffic accidents. (Though if you changed the examples, you would probably find that people have always been bad at comparing risks.)

The essay takes in Shakespeare's The Winter's Tale, tabloid-newspaper fearmongering and a spiffy virtual-reality paranoia test, and ends by heartily recommending cognitive behavioural therapy. Still, I couldn't help wondering whether the book protested too much. Paranoia, the authors intone, "permeates our society, more than we've ever suspected and possibly more than ever before". Doesn't that sound a little, er, paranoid?