CICERO once said that “Nature has planted in our minds an insatiable desire to see the truth.” These days it would be truer to talk of an insatiable desire to check our e-mail and Twitter accounts, and to play a few games of Candy Crush Saga (as a British parliamentarian was recently caught doing during a committee meeting). It is reckoned that four-fifths of smartphone owners check their devices within 15 minutes of waking up, and that the typical user does so 150 times a day.This time it is not nature but man that has done the planting. Internet entrepreneurs devote a lot of thought to getting people hooked on their products. How else can they survive in a world in which hundreds of new ones are launched every day? And smartphones and tablets have helped greatly: what could be more habit-forming than devices that are always evolving, always there and always buzzing with fresh diversions?