In “A Manifesto for the Truth” published in German news magazine Der Spiegel on Sunday, Snowden said current debates about mass surveillance in many countries showed his revelations were helping to bring about change.

“Instead of causing damage, the usefulness of the new public knowledge for society is now clear because reforms to politics, supervision and laws are being suggested,” the 30-year-old ex-CIA employee and NSA contractor wrote.

“Citizens have to fight against the suppression of information about affairs of essential importance for the public. Those who speak the truth are not committing a crime.”…

Society, said Snowden, could only understand and keep a check on these problems via an open, ruthless and informed debate.

He said some governments that felt exposed by the revelations had at first launched a “persecution campaign” to repress debate by intimidating journalists and threatening them with prosecution.

“At that time the public was not in a position to judge the usefulness of these revelations. People trusted that their governments would make the right decisions,” he said.