ON SUNDAY the secretary of homeland security, Tom Ridge, announced that his department had "new and unusually specific information about where al Qaeda would like to attack," coming from sources that provided intelligence of a quality "rarely seen." He provided the public with a list of five likely targets, including the World Bank and International Monetary Fund buildings in Washington. Security measures around those buildings were duly increased.

On Monday law enforcement officials were telling the media -- mostly off the record -- that the intelligence showed the existence not of an ongoing plot but rather of an old al Qaeda surveillance operation dating several years. Some said it did not warrant a raised security alert and closed streets.

On Tuesday the White House restated its case, pointing journalists toward additional sources of intelligence that hadn't been revealed on Sunday. According to Mr. Ridge, "The detail, the sophistication, the thoroughness of this information, if you had access to it, you'd say we did the right thing."

The trouble is, we don't have access to that information, and therein lies the difficulty for the public, the police and the intelligence officers who are trying to reveal as much of what they know as they can, and trying to prevent another cataclysmic terrorist attack at the same time. By its very nature, intelligence is vague: If it were not, the FBI presumably would have foiled the plot and arrested the plotters. But the vagueness of intelligence puts a special burden on those who seek to convey it to the public and the police.

Much of this confusion could have been avoided if, for example, Mr. Ridge and the intelligence officials who provided the original background briefings had been clearer about the significance, age and multiple sources of the new material: both "old" surveillance information that al Qaeda gathered before Sept. 11, 2001, as well as separate, powerful evidence of ongoing operations, which could not be presented in the same detail. Part of the problem is also Mr. Ridge's inability to resist boosterism in his public pronouncements, whether through references to the president's "leadership" or to his own department's achievements. At least one part of the difficulty DHS faces in telling the public about terrorist threats, however, is not of Mr. Ridge's making: the credibility gap that this administration suffers because of past intelligence failures.

Nevertheless, it is worth noting that the intelligence officials who have described this information are apolitical professionals who believe they have made significant gains in their understanding of al Qaeda's methods in the past few days. They are not well served by a homeland security bureaucracy that continues to struggle to find a believable and useful way to communicate with the public, nor by an administration that has misinterpreted intelligence. But their efforts to protect the nation from a genuine threat should not be minimized.