At the Plough and Stars in Cambridge, Massachusetts, I once heard an Irish banjo-player fly into a rage at someone’s refusal to stand him a ninth drink. ‘I play me music for nothin’,’ he explained. ‘And what do I get for it? Fock all!’ Maybe Michael Sandel, who teaches government at Harvard, just down the street, has met him. Sandel’s new book, What Money Can’t Buy, describes a confusion that is widespread even among policymakers and other putatively sober people: what should we do only out of love or duty, and what should we expect to get paid for?

There are still things money can’t buy, but the list gets shorter all the time. Walmart takes out insurance on the lives of its workers. New York theatre-goers hire professional queuers to collect free tickets to Shakespeare in the Park. Some right-wing lady in the American South is offering drug-addicted