YESTERDAY, GLENN GREENWALD made what I think is the most essential point about classified information and national security: Governments can, and all too often do, cover up their own venal and illegal acts by using the claim of national security to remove from public scrutiny any information that would reveal that wrongdoing. That makes leaks of classified information critical to democracy. Without principled whistleblowers within the government who disclose secret information about policies and actions that have the potential to harm the public interest, this country would have descended into tyranny long ago.

And that is the real reason why the Bush administration is so apoplectic about Mary McCarthy: She revealed information about legally and ethically questionable policies that Bush would never have been able to implement if they had been subject to public scrutiny.

All of the leaks about which Bush followers are so upset have a common attribute - they all reveal conduct by the government which is highly controversial and, in many cases, opposed by most citizens. None of the leaks falls into the category of the clear-cut case where national security is harmed without any public interest being served (the classic example being the advanced disclosure of troop movements, which is designed only to help the enemy without sparking any serious debate over a legitimately controversial issue). All of the leaks which are targeted by Bush followers for outrage and criminal prosecution all exposed government misconduct while avoiding any genuine national security harm. Their most significant impact, by far, was on the political front, not the security or military front.

There is virtually no significant government scandal in our country's history which did not rely upon disclosure of classified information to the press in order to expose the government's misconduct. The illegality of the Nixon administration was exposed almost exclusively through leaks by government employees of classified information, and virtually every Clinton scandal was achieved via leaks of classified and other secret information by sources hostile to the administration. Leaks of classified information are a critical part of how we check abuses on government secrecy; both sides have always used them and still do; and the government's power to punish leakers -- when used selectively and aggressively -- becomes the power to conceal one's wrongdoing.

If we had the society which Bush followers are seeking to impose -- where anyone is imprisoned who discloses, or writes about, any information marked "classified" by the government -- Watergate misconduct would never have been exposed. We would not know that the administration was eavesdropping on us without warrants in violation of the law. We would not know that our government systematically used torture as a routine interrogation device nor that it disappeared terrorist suspects to black prisons. And we would not have learned of the substantial doubts which existed, and the evidence bolstering those doubts, regarding Saddam's weapons capability prior to our invasion. Nor, for that matter, would we have recently learned about the administration's apparently advanced plans to wage war on Iran.

These types of unauthorized disclosures, more than anything else, are what accounts for the fact that Americans finally realized what type of government we really have, and caused literally millions of Americans to abandon this President and his administration. Is it really any wonder why the president's followers are so eager to imprison the people responsible for these types of leaks, while insistently ignoring the leaks designed to help the president? This has nothing to do with national security or with safeguarding classified information. It is about punishment, vengeance, and deterrence -- all focused on those who have exposed, or who could expose, government misconduct that results in political harm to George Bush.