Last week's groundbreaking reporting by The Guardian and The Washington Post exposed an NSA surveillance system of breathtaking scale, breadth, and depth. Even if legal under some tortured interpretation of the law, this system leaves the Fourth Amendment an empty vessel. The sheer audacity of the NSA surveillance and the complicity of segments of all three branches of government and the private sector suggest that we need a basic re-evaluation of intelligence operations on the scale of the Church Committee in the post-Watergate era. On Sunday, The Guardian disclosed—at his request—that the source of the leak was Edward Snowden, a 29-year-old former technical assistant at the CIA and current employee of a defense contractor.

The president's defense of the surveillance programs last Friday depended on our trust in congressional oversight and judicial process. These made the program legitimate, he argued, as he doubled down on his aggressive denunciation of the whistle-blowing that exposed the abuses. The president's defense, however, merely underscores the subversion of checks and balances by the post-September 11 constitution. It is precisely when traditional checks and balances fail that the fourth estate is so crucial.

Secrecy breeds error

Secrecy undermines the foundation of learning: criticism. People on the inside of the national security establishment cannot be trusted to make reasonable judgments—not because they are bad people (one assumes that, for the most part, they are deeply committed and well-intentioned)—but because they inhabit a deeply error-prone system that lacks the basic elements of self-correction. Saddam Hussein is dead today because he created a system in which no one could tell him that if he kept obscuring the fact that he had no WMD, he would die.

Open societies thrive not because they have smarter people, or better armies, or perfect markets. They thrive because, in their very imperfection, they enable continuous learning. Open societies can’t always act as effectively as non-open societies. For a while, planned economies looked like they were better at putting Sputnik in orbit, and spy agencies unfettered by democratic qualms, we feared, could foment revolution from Korea to Cuba. But in the long run, openness made us learn, adapt, and become better. That is why, eventually, either China will open up or America will continue to lead into the twenty-first century. But only if we stay an open society.

Secrecy has been allowed to metastasize under the Bush-Obama national security system. As the FISA Court order to Verizon showed, even the operation of the law is secret. The Department of Justice issues secret memos; these become unchallenged interpretations of law that FISA Court judges are asked to endorse without the benefit of an opponent's criticism. Any good lawyer knows that if you read the briefs of one side only, they seem overwhelmingly persuasive—until you read the other side's brief. These decisions, in turn, remain secret, and thus immune to criticism even after they have been issued. And that complete immunity from criticism insulates them from good reason. They are, by design, hobbled, incapable of embodying good judgment.

Congressional oversight suffers from similar information imbalances. When Senators Feinstein and Chambliss tell us that the intelligence gathered is invaluable and the civil rights violations minimal, we cannot trust their judgment: Their honest judgments reflect information that is one side's brief for its own perspective. Legislators can work their way out of this dynamic in extraordinary cases, but such divergence is not the normal course. Congressional overseers who come with a critical frame of reference and interpret the information skeptically—like Senators Wyden and Udall, who obliquely raised the alarm for years—are caught in a Catch-22: They can only learn enough to criticize knowledgeably by signing away their freedom to criticize publicly.

We’re told to trust the government’s surveillance package as a whole, as a black box. But when we see two products of that opaque system that are so totally out of whack with the proper balance between national security and constitutional rights, we can have no confidence in the system. Asking us to simply trust the black box is a completely inadequate response.

The torture program was enabled by spooks cooperating with national security types in the executive manipulating the information available to the select few who participated in congressional oversight and wildly overstating the value of their work. The Senate Select Committee on Intelligence report on the incompetence, dissimulation, and sheer futility of that program remains a national security secret. But we know the basic storyline. And there is absolutely no reason to believe that the system of checks and balances that failed so spectacularly there has performed impeccably here, or that the self-affirming assertions of the spies about the critical value of their work are systematically more credible.

Only a genuine, aggressive, independent, and transparent review process can restore the confidence necessary to maintain security under the American Constitution. We need a new Church Committee to assess the NSA's work in this post-September 11, big data moment.

The public-private partnership for social surveillance control and big data

The public-private surveillance partnership has reached a degree that would have sounded like conspiracy theory mere weeks ago. If you have ever seen an advertisement pop up on your laptop screen for something you were just searching for on your smartphone, you've encountering the tip of the big data iceberg. Marketing is at the forefront of combining big data with behavioral sciences: The New York Times last year described how Target had figured out how to infer from purchase data that a customer was pregnant, and used this insight to persuade soon-to-be moms that Target was the best one-stop shop. What we learned last week is that the NSA also knows that you're pregnant, maybe before you’ve even told your parents. The leaks suggest that the NSA actually has deeper data than any of these private companies, because it has direct access to data from almost all of them.

Imagine if your Google searches, e-mails, Facebook messages, and Skype calls all fell under the control of a single entity, which employs some of the world's best mathematicians and behavioral scientists to make sense of this wealth of data. Each company by itself likely knows more about your health risks or secret desires than you are willing to admit to yourself. What the NSA can know by cross-referencing these sources is mind-boggling. No secret service in the history of the world had feelers into so much of society's life. Even if every neighbor spies on the lives of others, the sheer imperfection of analog life makes it impossible to know or predict as much as our ubiquitously computerized society makes possible.

What makes this new public-private partnership work is the American constitutional structure of the early twenty-first century. Privacy law experts have long explained that Europe protects against private surveillance, but permits more government surveillance, while the U.S. is the opposite. Our lax control of what private companies can collect has underwritten the creation of some of the world's most invasive surveillance and analysis techniques in the name of marketing and consumer sovereignty. But now we learn that our panic-stricken response post-September 11 has created a constitutional structure that has given us the worst of both worlds.

The technology companies named in the PRISM presentation have all denied cooperating with the program, or even knowing about it. What should we believe? We have two options. One is that the companies are telling the truth and that the U.S. government has for seven years hacked into the systems of some of the country's biggest companies. The other option is that the U.S. government used a combination of secret court orders, promises of immunity, and appeals to patriotism to get technology companies to cooperate. Whichever interpretation you think more likely, there seems little doubt that the NSA program reveals a deep danger caused by the levels of private surveillance that our law permits.

The fourth estate and the morality of whistleblowers: Shoring up the last line of defense

The critical role that the press and the whistleblower played last week underscores the threat that the Obama administration's scandalous assault on press freedom poses to American democracy. The only reason we now know more about the scope and scale of the Bush-Obama surveillance state is that one young man, Edward Snowden, consciously took the risk of lengthy imprisonment to leak these materials, and that reporters and editors were not cowed by the threat of being considered criminal co-conspirators.

If we learn anything from the events of the past week, it is that journalists and their sources are the safety valve of last resort when the other three branches have failed to protect the American people and our constitution. Nowhere is secrecy so great, and the checks and balances of the three branches so fragile, as in national security. There, more than anywhere, we need a robust fourth estate. That is what the First Amendment's freedom of the press is for. Snowden has given us the gift of public accountability and the possibility to have a more open, democratic debate about the post-September 11 national security constitution. His disclosures just may be the kind of wakeup that shakes us out of the Bush-Obama constitutional panic response, just as the Army-McCarthy hearings and Watergate shook us out of earlier great national security constitutional stumbles.

Yochai Benkler is is a professor at Harvard Law School and co-Director of the Berkman Center for Internet and Society at Harvard.