Taken together, the [Edward Snowden] revelations have brought to light a global surveillance system that cast off many of its historical restraints after the attacks of Sept. 11, 2001. Secret legal authorities empowered the NSA to sweep in the telephone, Internet and location records of whole populations. Six months after the first revelations ... Snowden agreed to reflect at length on the roots and repercussions of his choice. He was relaxed and animated over two days of nearly unbroken conversation. Snowden offered vignettes from his intelligence career and from his recent life as an indoor cat" in Russia. But he consistently steered the conversation back to surveillance, democracy and the meaning of the documents he exposed. "For me, in terms of personal satisfaction, the mission's already accomplished," he said. "I already won. As soon as the journalists were able to work, everything that I had been trying to do was validated. Because, remember, I didn't want to change society. I wanted to give society a chance to determine if it should change itself. All I wanted was for the public to be able to have a say in how they are governed," he said. Snowden ... had come to believe that a dangerous machine of mass surveillance was growing unchecked. Closed-door oversight by Congress and the Foreign Intelligence Surveillance Court was a "graveyard of judgment," he said, manipulated by the agency it was supposed to keep in check. The NSA's business is "information dominance," the use of other people's secrets to shape events. At 29, Snowden upended the agency on its own turf.