IT IS DIFFICULT not to look cynically upon the timing of President Bush's dramatic unveiling of a plan for a Cabinet-level Department of Homeland Security, announced Thursday night.

But such cynicism, however appropriate, would miss the larger point and might well muddle more significant questions that must be asked about the proposed department.

First: Does the country need a centralized department to combat terrorism? And if so, is this the way to organize it?

Right now, the answers to those questions run the gamut from "could be" to "maybe."

That's why Connecticut Sen. Joseph I. Lieberman's suggestion that Congress skip public hearings on the plan and fast-track its passage is unwise. Mr. Lieberman, a Democrat, is sponsor of a similar, if less far-reaching, proposal in Congress. But supporting the concept ought not translate into the rubber-stamping of a complex and apparently hastily assembled plan for a new Cabinet agency that, if organized badly, would only add to the chaos.

And chaos seems not too strong a word to describe the lack of coordination, information-sharing and plain common sense endemic in the agencies charged with the nation's security before Sept. 11. Say what the White House will, it is no coincidence that the president's announcement came at the end of the first day of hearings on Capitol Hill outlining the scope and nature of those agencies' failure.

Clearly, what had passed for this nation's defense against terrorism wasn't working; President Bush admitted as much in his speech Thursday. Not so clear, however, is how to fix it.

The administration proposal calls for the creation of a Cabinet department that would absorb some 22 or more existing federal programs and agencies, grouped into four broad areas of national security. Agencies as disparate as the Coast Guard (border and transportation security) and the Lawrence Livermore National Laboratory (chemical, biological, radiological and nuclear countermeasures) would come under the new department. So would the Federal Emergency Management Agency, perhaps best known to Americans as the feds to call when a hurricane hits.

The idea, apparently, is that putting such agencies under one organizational roof will clarify their mutual anti-terrorist mission and allow them to better coordinate their efforts. But how will their being in the same massive department -- one that will employ almost 170,000 people -- make that difference? Will they still be performing their non-security-related functions, even though they are in the Department of Homeland Security? And will it be worth the huge job of reorganization in an already over-bureaucratized federal system to achieve that goal?

As the American people have learned in the last few weeks, perhaps the most fundamental flaw in this country's intelligence operations before Sept. 11 was that the FBI and the CIA were operating in a culture of secrecy, power-hoarding and strict hierarchical command. Much of that is necessary, of course. But they were keeping secrets from each other. Yet neither of those agencies will be part of the administration's proposed Homeland Security Department.

The group of agencies bunched under "information analysis and infrastructure protection" will have access to "distilled reports" from the CIA and FBI, but they had that before. How is this an improvement?

Congress must work quickly -- but most important, thoroughly -- to find the answers to these and other questions about the president's proposal.

This may be the best way to shield the country from another terrorist attack. But if it isn't, our elected senators and representatives must say so. Because the last thing this country needs is yet another bureaucracy serving as a distraction from what Americans most rely on their government to do -- protect them from their enemies.