Nobody can disagree with the proposition that the press and the public have a vital interest in open government. Founding Father James Madison famously observed that democracy without information is "but prologue to a farce or a tragedy." But Madison also participated in the Constitutional Convention of 1787, which kept its proceedings secret to avoid premature public disclosure of its deliberations. Many historians view that secrecy as the key to the convention's success. While governments may hide behind closed doors, U.S. democracy was also born behind them.

It is not enough, then, to reflexively call for transparency in virtually all circumstances. The right amount is debatable, even for those who, like Madison, understand its utility. And so, the right question about the Freedom of Information Act is: "How much of it should we have?" Should information that is of use to citizens be disclosed if it might be of use to terrorists? That's not easy to answer.

Consider one example: Legislation that exempts from public disclosure information supplied by businesses regarding potential terrorist attack risks. To be sure, this exemption can be abused - citizens concerned about risks in their community are deprived of information, and corporations might hide relevant non-critical information under a false flag of "security."

But, just as surely, supplying this sort of information to the government is vital to ensure that critical infrastructure is protected. And disclosing information about these risks is dangerous, as terrorists might use it to harm the very citizens that governmental openness is intended to protect. Thus, total openness defeats one purpose of disclosure - keeping citizens safe - while total closure permits government misuse.

What's required is calibrated transparency, a measured, flexible transparency suited to the needs of oversight without frustrating legitimate limits. Calibrated transparency means that sometimes the public's right to know doesn't include everyone, but, for example, only our elected representatives.

That's not a perfect solution. But it provides the balance we need. After all, why do we seek transparency in the first instance? Not for its own sake. Without need, transparency is little more than voyeurism. Rather, the reason for transparency is oversight - it enables us to limit the executive exercise of authority. In the post-9/11 world, the form of that oversight must vary depending upon the extent to which transparency and opacity are necessary to the executive powers.

In short, Madison was not a hypocrite. Rather, opacity and openness each have their place, in different measures as circumstances dictate. The wisdom of Madison's insight - that both are necessary - remains as true today as it was more than 200 years ago.

Paul Rosenzweig is a senior fellow in the Heritage Foundation Center for Legal and Judicial Studies and a former Justice Department lawyer.