By now, almost everyone knows what Edward Snowden did. He leaked top-secret documents revealing that the National Security Agency was spying on hundreds of millions of people. The key to Snowden's effectiveness, according to Thomas Devine, the legal director of the Government Accountability Project (GAP), was that he practised civil disobedience" rather than "lawful" whistleblowing. "None of the lawful whistleblowers who tried to expose the government's warrantless surveillance ... had any success," Devine told me. "They came forward ... but the government just said, 'They're lying. We're not doing those things.' And the whistleblowers couldn't prove their case because the government had classified all the evidence." The NSA whistleblowers were not leftwing peace nuts. They had spent their professional lives inside the US intelligence apparatus - devoted, they thought, to the protection of the homeland and defense of the constitution. They were political conservatives, highly educated, respectful of evidence, careful with words. And they were saying, on the basis of personal experience, that the US government was being run by people who were willing to break the law and bend the state's awesome powers to their own ends. They were saying that laws and technologies had secretly been put in place that threatened to overturn the democratic governance Americans took for granted and shrink their liberties to a vanishing point.