Whether he is a scoundrel or a hero, it is clearer all the time that Edward Snowden has done us a good turn. Shortly before Mr Snowden’s first big download in June, President Barack Obama gave a landmark speech in which he defended the US war on terror while pleading for vigilance against its excesses. Franklin Roosevelt once said: “I agree with you. I want to do it. Now make me do it.” Though Mr Obama was talking about America’s counter-terrorist and data intelligence complexes, his speech contained a similar appeal. Shortly afterwards, Mr Snowden took him up on the challenge.

Mr Obama has yet to provide a convincing response – ask Brazil’s Dilma Rousseff, or Germany’s Angela Merkel. Mr Snowden may yet force him to. From Mr Obama’s point of view there are silver linings to the National Security Agency bombshells. Something of this kind was going to happen sooner or later. If a high-school dropout could get hold of troves of classified information, so can many others. Bradley Manning, a US army private, had already demonstrated that. US intelligence agencies are meant to be smart. Mr Obama now knows how dumb they can be.

Mr Snowden has also reminded us that there is more at stake over America’s sprawling data intelligence complex than hunting terrorists. Washington has done a good job of preventing big attacks on the US homeland since the terror attacks of September 2001. Both George W Bush and Barack Obama deserve credit. Both also deserve blame for having over-learned the lessons of 9/11. US intelligence does not have a particularly stellar history. It has a tendency to bungle covert action and to miss what is coming – from the Bay of Pigs debacle in Cuba to the World Trade Center attacks. There is also its extraordinary litany of domestic abuses exposed by the Church committee in the 1970s.